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MazdaSpeed 3/6 - Suspension & Brakes Discussion for suspension items like coilovers, springs, sway bars, mounts,chassis bracing and brakes.


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 Old 09-25-2014, 02:39 PM   #121
 
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I made the level pads in my 1-car garage. I simply outined the tire contact surface, then used taunt fish line and a level.

Knowing the floor sloped down toward the door, I checked the slope and decided it was negligible, considering the measurments I wanted to do. I 1st checked across front outlines, measured gap, and used a stack of thin plywood & laminate to shim an oversized footprint. Then went to the back, and repeated the process. Marked 2 of the 4 contact squares with shim height, & marked shims as to where they went.

Camber: drop line down by wheel ctr, measure difference in offset from common wheel points, then used arctan to get angle in degrees.

Toe: taunt string attached to jack stands, both sides of car. Tedious!

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 Old 09-27-2014, 10:46 AM   #122
 
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Originally Posted by phate View Post
I still have the stock front bar, and I think I'll leave it for now. When I moved the rear bar to the stiffer setting, I noticed more front end grip - it felt better and it started to heat the outside of the tires more than it had been (even though there is more total roll stiffness). I think it's just too much front bias right now. Since I put the suspension on, we've noticed the front tires are getting worked much harder than the rears, in terms of wear. I'm going to continue increasing the rear roll stiffness while leaving the front (for now), because it seems to make the front tires much happier, and I have available play items in the rear to offset the reduced grip from the extra load. Meaning I think I'll be able to bring up front grip while maintaining rear grip.

I put together my own suspension calculator (based on Staniforth's methods) that includes calculations for roll stiffness/roll stiffness proportion, weight transfer, tire loads, roll angle, and suspension frequencies. I think we discussed it a bit in this thread - it's the one I made that doesn't include ARB info; but not knowing the rate of the WL bar (since it has multiple bends...and not knowing if the standard formulas apply) makes it moot. If I can ever get a few weights, I'll test and add that section to the calculator........
Thanks for putting up the static side shot of the car, the visual really helps put things in perspective. Based on the dynamic pics, it appears to be more biased as a highly tuned DD, vs a highly tuned autocross car. Meaning there is more roll that would make turn in damped, and braking dive may induce alignment changes at turn in.

I agree with your prior post about going with stiffer springs. FCM spec'd a softer rear spring than all the racers (some being engineers too) that wrote books, including Staniforth, would have suggested. And you are now running an upgraded rear bar at the stiffest setting, likely to compensate for the excessive rear MR used by FCM. I suggest plugging in the actual rear MR in your Excel program to see what it suggests for a rear spring, based on Freq. It also would be interesting to run your program with FCM' rear MR, and see if you get the same springs based on freq.

The Staniforth method was challenged in a couple forums regarding redundent use of the sprung mass at the central CG, as well as the components of this mass over the axles at their local CG. I think the doubters were wrong, but I would just verify the Staniforth method has the CG of the sprung weight about 60% toward the front, with a lever arm down to the roll axis to form the "roll couple" or "Roll Moment". And the front and rear componets of the total sprung mass just become G forces acting at the F & R roll centers, with lever arms down to the pavement.

About the rears way bar stiffness, it could be measured, or calculated. I derived the basic formula (created by Fred Puhn) for a simple sway bar, using beam theory. I figure I could modify the formula to account for the extra flex from the huge central offset. But I bet a spring rate tester could be used to measure the bar rate, with some creative jigging. We spoke of other ways to do the measurment:

Bar rate measurment on car

Another way would be to get a friend from work to do a simple beam model of the bar in about 1/50th the time needed to alter the Puhn formula. Once the rate is measured, it can be scaled for another diameter. If it is modeled using FEA, checking another dia would just take a quick change in the input file material properties. Of course an acurate sketch of the bar and holes would be needed.

.
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 Old 09-28-2014, 09:22 AM   #123
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Originally Posted by KevinK2 View Post
Thanks for putting up the static side shot of the car, the visual really helps put things in perspective. Based on the dynamic pics, it appears to be more biased as a highly tuned DD, vs a highly tuned autocross car. Meaning there is more roll that would make turn in damped, and braking dive may induce alignment changes at turn in.

Spring rates were chosen based on target frequencies, not overall roll resistance. That was the priority, and I stuck with it. Considering the limited choice of ARB's, it would take a lot more spring to bring the roll gradient down and maintain a decent roll resistance bias (there are huge front ARB's, but not any rear ARB's). Too high of spring rate can and does result in reduced grip.

I agree with your prior post about going with stiffer springs. FCM spec'd a softer rear spring than all the racers (some being engineers too) that wrote books, and Staniforth would have suggested. And you are now running an upgraded rear bar at the stiffest setting, likely to compensate for the excessive rear MR used by FCM. I suggest plugging in the actual rear MR in your Excel program to see what it suggests for a rear spring, based on Freq. It also would be interesting to run your program with FCM' rear MR, and see if you get the same springs based on freq.

I've done that and it results in a pretty high rear spring requirement to the tune of 1,100lb/in - nearly double what I'm currently running. Considering the amount of rotation I currently have, I bet the car would be way too loose and ultimately slower. I still think Shaikh was correct in his MR adjustment based on actual bounce frequency - flat ride is achieved with the current setup, and it wouldn't if the bounce frequency was significantly lower like the mechanical MR suggests. It actually seems to occur at a slightly higher speed than what I need (2nd gear maxes out at 62mph int he current setup) so going with a higher rear spring rate will bring that down a bit. I considered that might happen when I ordered springs, so it's not a surprise.

The Staniforth method was challenged in a couple forums regarding redundent use of the sprung mass at the central CG, as well as the components of this mass over the axles at their local CG. I think the doubters were wrong, but I would just verify the Staniforth method has the CG of the sprung weight about 60% toward the front, with a lever arm down to the roll axis to form the "roll couple" or "Roll Moment". And the front and rear componets of the total sprung mass just become G forces acting at the F & R roll centers, with lever arms down to the pavement.

.
At this point, my choice is to increase rear spring rate to increase the rear roll stiffness. I don't see much of a downside to this right now.
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 Old 09-28-2014, 11:44 AM   #124
 
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Originally Posted by phate View Post
At this point, my choice is to increase rear spring rate to increase the rear roll stiffness. I don't see much of a downside to this right now.
You may not be limited to the 28.5 mm front sway bar upgrade. Steeda makes a high quality 26mm front bar.

Steeda 26mm front bar

MS6 Sway Bar Analysis

It's for the Fusion and M6, but, since Racing beat lists a 28.5mm bar for the M6 and the MS6, it is possible the 26mm will fit the MS6 too.

Racing Beat 28.5mm front bar


Regardless of bars, simply designing to a higher frequency for about a 20-30% change in rates would reduce dive. If the 26mm front bar fits, the % increase in both the front and rear bar over stock sizes would be 40%. That would not change the Tot-WT-balance very much, compared to a 28.5 front bar.

Originally Posted by phate
I've done that and it results in a pretty high rear spring requirement to the tune of 1,100lb/in - nearly double what I'm currently running. Considering the amount of rotation I currently have, I bet the car would be way too loose and ultimately slower.
Agreed

I still think Shaikh was correct in his MR adjustment based on actual bounce frequency - flat ride is achieved with the current setup, and it wouldn't if the bounce frequency was significantly lower like the mechanical MR suggests.
Based on the car I won my class in, the last 2 of 3 years competeing, before I went for HPDE fun, the pic's are not as flat as I was cornering and hard braking. And videos from the nationals seemed to show stiffer suspensions. I am not suggesting rediculus rates for no roll, rather a modest increase in most rates. But if you like it as is, that's all that matters.

EDIT 9-29: How did Shaikh measure the rear bounce freq? I would think with both shocks released, and checking the rear bounce rate, vs a corner test. But even that does not simulate the freq calc, which represents taking the corner weight as a lumped mass on a spring, which reflects a primary rigid body motion (pure up and down) vs the higher order secondary mode (only rear goes up and down) that happens with the test I described.

It actually seems to occur at a slightly higher speed than what I need (2nd gear maxes out at 62mph in the current setup) so going with a higher rear spring rate will bring that down a bit. I considered that might happen when I ordered springs, so it's not a surprise.
Ok I'm ready for a lesson
How will increasing the rear spring rate from the current set-up reduce your max speed in 2nd gear?

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 Old 09-28-2014, 11:57 AM   #125
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See my notes in red about proportion of roll resistance. I don't want to increase load transfer across the front axle, so anything more up there is out of the question right now.
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 Old 09-28-2014, 01:57 PM   #126
 
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Understood, and if you are commited to a frequency basis, nothing could be done with the 26mm bar. But if the rear spring rate was increased to compensate for the 40% stiffer front bar, the reduced roll would help preventing any rear wheel lift you perceived.

I'm sorry if I was not clear about the calculators. One question was how well your version agreed with FCM's frequency method, on spring rates, with the larger MR chosen by FCM.

Just a reminder, you have done a mega job creating this suspension build thread! With all your precise measurements, anyone could now do a full design with the two online programs I mentioned.

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 Old 09-30-2014, 11:19 AM   #127
 
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Possible +2mm front sway bar (26mm). Would require stiffer rear springs. Results:

1) less body roll, quicker response at turn-in.
2) with WL rear bar at stiff setting, both bar rates are 40% stiffer vs OEM.
3) less likely to lift rear wheel at a tight corner.

Then to offset the stiffer roll up front, rear spring rates would need to be increased (unless you can find the 25mm corksport and add a stiffer hole to it, and trim off the end).

Steeda 26mm Fusion and Mazda6 Front Bar:



Similar to bar designed for the MS6:

AutoExe_MS6_Front_Sway_Bar
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 Old 09-30-2014, 12:13 PM   #128
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Damnit, quit editing posts hours after you've posted. I come back and there's half an extra post 3 posts up.


Originally Posted by KevinK2 View Post
Possible +2mm front sway bar (26mm). Would require stiffer rear springs. Results:

1) less body roll, quicker response at turn-in.
2) with WL rear bar at stiff setting, both bar rates are 40% stiffer vs OEM.
3) less likely to lift rear wheel at a tight corner.

Then to offset the stiffer roll up front, rear spring rates would need to be increased.

Steeda 26mm Fusion and Mazda6 Front Bar:



Similar to bar designed for the MS6:

AutoExe_MS6_Front_Sway_Bar
I am going to stiffen the rear first before stiffening the front. Stiffening the front is not out of the question, but I'm not there yet. Small iterations will be made from here. I don't see any other way of doing it without introducing too many variables at any one time.

There are 4 springs from QA1 that fit our cars with very little work and no modification. None of the big spring manufacturers make a spring that will work without making custom adapters or having custom springs wound. It's not like I'm running, or could run, a 2.5" ID spring back there. There are limitations here that you are completely overlooking or don't know of. The 600lb/in rear springs I have are the second stiffest spring available. The 700lb/in springs are the stiffest available. If I can't balance out the car with the 700's and WL bar on the stiff setting, it's going to require a different approach and that approach won't include stiffening the front at all.






Originally Posted by KevinK2 View Post
You may not be limited to the 28.5 mm front sway bar upgrade. Steeda makes a high quality 26mm front bar.

Steeda 26mm front bar

MS6 Sway Bar Analysis

It's for the Fusion and M6, but, since Racing beat lists a 28.5mm bar for the M6 and the MS6, it is possible the 26mm will fit the MS6 too.

Racing Beat 28.5mm front bar


Regardless of bars, simply designing to a higher frequency for about a 20-30% change in rates would reduce dive. If the 26mm front bar fits, the % increase in both the front and rear bar over stock sizes would be 40%. That would not change the Tot-WT-balance very much, compared to a 28.5 front bar.

Agreed



Based on the car I won my class in, the last 2 of 3 years competeing, before I went for HPDE fun, the pic's are not as flat as I was cornering and hard braking. And videos from the nationals seemed to show stiffer suspensions. I am not suggesting rediculus rates for no roll, rather a modest increase in most rates. But if you like it as is, that's all that matters.

EDIT 9-29: How did Shaikh measure the rear bounce freq? I would think with both shocks released, and checking the rear bounce rate, vs a corner test. But even that does not simulate the freq calc, which represents taking the corner weight as a lumped mass on a spring, which reflects a primary rigid body motion (pure up and down) vs the higher order secondary mode (only rear goes up and down) that happens with the test I described.



Ok I'm ready for a lesson
How will increasing the rear spring rate from the current set-up reduce your max speed in 2nd gear?

.




Let me add some context to that quote you pulled:

flat ride is achieved with the current setup, and it wouldn't if the bounce frequency was significantly lower like the mechanical MR suggests. It (the point where flat ride is achieved, in terms of speed) actually seems to occur at a slightly higher speed than what I need (2nd gear maxes out at 62mph int he current setup) so going with a higher rear spring rate will bring that (the point where flat ride is achieved, in terms of speed) down a bit. I considered that might happen when I ordered springs, so it's not a surprise.

What car did you set up and win in, and what class did you win? Was it nationals, like you're implying? No one here knows anything about what you've done or even who you are. If you need a more direct question: why should we listen to anything you have to say about how to set up a car? You've brought up a few good points in this thread and others, but you harping on one thing over and over or you giving very general suggestions (some of them aren't even suggestions, they're just you talking about something somewhat related) doesn't really move the conversation forward. We're on the internet and you could be some 16 year old kid who's really good at Googling stuff. I don't think that's the case, but you get the idea.
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 Old 09-30-2014, 01:54 PM   #129
 
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Originally Posted by phate View Post
Damnit, quit editing posts hours after you've posted. I come back and there's half an extra post 3 posts up.
I simply added descriptive content to the question I had asked, with the hope that you would answer the question about a test method, which is still unanswered. I do appeciate it when you provide answers in a discussion, but I'm sorry if I was overbearing in that case.

I am going to stiffen the rear first before stiffening the front. Stiffening the front is not out of the question, but I'm not there yet. Small iterations will be made from here. I don't see any other way of doing it without introducing too many variables at any one time.
Agree.

There are 4 springs from QA1 that fit our cars with very little work and no modification. None of the big spring manufacturers make a spring that will work without making custom adapters or having custom springs wound. It's not like I'm running, or could run, a 2.5" ID spring back there. There are limitations here that you are completely overlooking or don't know of. The 600lb/in rear springs I have are the second stiffest spring available. The 700lb/in springs are the stiffest available. If I can't balance out the car with the 700's and WL bar on the stiff setting, it's going to require a different approach and that approach won't include stiffening the front at all.
I know you have adjustable spring perches in the rear, I forgot you were still using variable diameter springs.

Let me add some context to that quote you pulled:

flat ride is achieved with the current setup, and it wouldn't if the bounce frequency was significantly lower like the mechanical MR suggests. It (the point where flat ride is achieved, in terms of speed) actually seems to occur at a slightly higher speed than what I need (2nd gear maxes out at 62mph int he current setup) so going with a higher rear spring rate will bring that (the point where flat ride is achieved, in terms of speed) down a bit. I considered that might happen when I ordered springs, so it's not a surprise.
I have never heard of "flat ride" issues, if you mean riding roughly, until you pass through the natural frequency the suspension was designed to. If that's the case, I suspect it is not an issue. Among other things, as a Certified PE in Mechanical Engineering, I designed many agitators for industrial use, and "natural frequencies" were a significant issue there, like when blade passing frequencies, relative to static baffels, could cause high amplitude excitation of the agitator.

I have never been in a car ( except my full race car, on a highway that had a rough ride due to rigid body mode vibration caused by drops at concrete joints ) where this was an issue. As I implied before, I don't know what issue you are worried about.

But it seems like a contradiction to say raising the rear spring rates, which increases the natural frequency at issue, will cause you to hit this "rough ride" point at a lower speed.

Answers to your last paragraph later, but here is a link to the "DP" 1968 GT-6 that I built by myself ( and the 3-spoke wheel I designed using Nastran & Patran and a stack of papers from Prof Hull at USC @ Davis), and the club I raced at for 3 years, and won my class the last two. I never said/implied/etc that I raced in the National Run Offs. Find a quote and I'll eat it.

group1 - MisterTool

Brandywine Motorsport Club

.
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 Old 09-30-2014, 07:21 PM   #130
 
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CanyonRider's Autox Pictures ..... seems to be less roll.

CanyonRider-autox-shakedown


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 Old 09-30-2014, 08:27 PM   #131
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I don't know how he measured the bounce frequency. I only asked him why it was different and that was his explanation. He said that he measured the mechanical ratio as ~.58 or .59, which is nearly what I measured at .57. He is aware of the discrepancy, but didn't offer any more than that.

Flat ride is how quickly the rear settles in relation to the front to reduce pitch, allowing the front and rear to settle at the same time. Flat ride sources:

Shaikh, himself, talking about flat ride:

^He touches on full bore race cars vs streetable vehicles in terms of frequencies at the end.

He also mentions Maurice Olley, which is where the idea comes from. A quick google search should bring up some good articles, many with some math that will take me a while to sort through I just pulled up a paper written by H Marzbani if you would like to take a look. It, of course, has many references that will also be helpful.




CanyonRider's 6 is ~300lbs less weight than my car. The last weight I saw for his car was 2,926lbs and mine comes in right at 3,340 in its current state. Also, last I knew, he was running 700/500 lb/in springs front/rear with a 27mm rear bar and 28.5mm front bar. I have no doubt that his car rolls less than mine. [He's also on asphalt in that picture, which is typically a far cry from the grip of the concrete I normally run on.]
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 Old 10-01-2014, 11:43 AM   #132
 
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[quote=phate;2715395]I don't know how he measured the bounce frequency. I only asked him why it was different and that was his explanation. He said that he measured the mechanical ratio as ~.58 or .59, which is nearly what I measured at .57. He is aware of the discrepancy, but didn't offer any more than that.[quote] thanks!

Flat ride is how quickly the rear settles in relation to the front to reduce pitch, allowing the front and rear to settle at the same time. Flat ride sources:

Shaikh, himself, talking about flat ride: Fat Cat Motorsports - What is Flat Ride and why should you care? Suspension design concepts - YouTube

^He touches on full bore race cars vs streetable vehicles in terms of frequencies at the end.

He also mentions Maurice Olley, which is where the idea comes from. A quick google search should bring up some good articles, many with some math that will take me a while to sort through I just pulled up a paper written by H Marzbani if you would like to take a look. It, of course, has many references that will also be helpful.
The term "flat ride" is the same as the more commonly used "settled ride" description of the ride after a fast change in the road surface, like a gradual speed bump. In the video,
Shaikh talks mostly about ride frequencies and some about "flat ride", but little about damping.

This is what is being refered to:



From: www.audizine.com Upgrading the Suspension

These are single event damping curves, based on fraction of "critical damping", which is where there is just enough damping to prevent any overshoot in the return stroke. Many can recal doing a shock test, giving an impulse to the rear bumper, and for american cars the ratio "zeta" from the graph is between .5 and .75. It is much less for that guy with no money, driving down the street in an old beater with a shock that has leaked out. That end of the car is bouncing at a low frequency around 1 hz.

We have discussed the ride frequencies, and the general rule is 10-15% higher freq in the rear, but in racing, there are exceptions as Greg Lockhart (automotive suspension engineer) discussed in this prior link:

eng-tips.com, frequency based design

CanyonRider's 6 is ~300lbs less weight than my car. The last weight I saw for his car was 2,926lbs and mine comes in right at 3,340 in its current state. Also, last I knew, he was running 700/500 lb/in springs front/rear with a 27mm rear bar and 28.5mm front bar. I have no doubt that his car rolls less than mine. [He's also on asphalt in that picture, which is typically a far cry from the grip of the concrete I normally run on.]
The bars is the major reason he rides flatter. I ran his spring and bar case through my 1995 spread sheet (Fred Puhn + Me), using true MR's, and he has 55% total weight transfer front bias, and a 52% Roll Stiffness bias, with a 63% front total weight bias. Roll at 1 G was less than 1 degress, not including tire rate, and s bar bushing flex.

Based on weight distribution, he has an abundance of rear roll stiffness. It would be great to run your car throught the program, if the rear bar stiffness could be determined, as I discussed before. If someone were to take careful measurments off a WL rear bar, or a stock bar with the lever arm lengths from a WL bar, I have a colleague from work who could quickly model the bar and determine stiffness, for both holes. I think he could use a solid-works input file.

For related documents, check part-1 and part-3 of the Tech Tips on Springs and Dampers:

http://www.optimumg.com/technical/technical-papers/

.
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 Old 10-05-2014, 03:35 PM   #133
 
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Originally Posted by phate View Post
Flat ride is how quickly the rear settles in relation to the front to reduce pitch, allowing the front and rear to settle at the same time.......

....He also mentions Maurice Olley, which is where the idea comes from. A quick google search should bring up some good articles, many with some math that will take me a while to sort through I just pulled up a paper written by H Marzbani if you would like to take a look. It, of course, has many references that will also be helpful....
Is the paper by H Marzbani at this site?

Flat Ride; Problems and Solutions in Vehicle : Nonlinear Engineering

This paper deals with the issue I was hinting at earlier in post #124 :

Originally Posted by Kevin
... the freq calc, which represents taking the corner weight as a lumped mass on a spring, which reflects a primary rigid body motion (pure up and down) vs the higher order secondary mode ....
The "frequency method" of spring selection is NOT a calculation related to the pitch motion the car actually goes through initially. Rather, it is a vertical bounce frequency, as I described in the quote above.

Based on the Abstract of Marzbani's paper, it seems like he is going after the for-aft pitch mode frequency of the actual rigid body vibration that occurs., when excited by a cross road "bump" at a limited speed. And yes, I would like to take a look. I think this is looking more at production suspension design, vs racing applications.

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 Old 10-05-2014, 03:47 PM   #134
 
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Dude do you just enjoy talking to yourself?

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We still have no idea who you are or why we should even pay attention to your rabble. It's also my understanding you don't even drive a ms6 so what you doing in here anyways

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 Old 10-06-2014, 08:13 AM   #135
 
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Who am I?

I drive an 04 Mazda6 5 dr. Based on my 20 year old suspension spread sheet, I tuned the suspension to perfection by just adding a 22.5mm rear bar, as the Excel spreadsheet predicted was necessary.

I spent 30 years as a Professional Mechanical Engineering Consultant for a large chemical company with plants all over the world. Working at a high level to solve problems in engineering mechanics, vibration, stress, etc at all, that the local engineers could not solve. On average each job I did resulted in $1-2 million dollars savings in more run time in oversold markets. I also was a guest lecturer at the University of Delaware in "Machine Design".

Based on 1000's of miles of big track time in 3 different cars, in 2007 I posted a MS6 alignment thread in a earlier forum, that had 90,000 views . And at Summit Point, I was solo-qualified for years, and asked to be an instructor ... I declined based on some crashes I saw where the instructor took a beating.

Alignment .. "in Spec" Not Good Enough - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum

In the same forum, I reviewed Mazda's publication on the MS6 AWD, and showed non believers at the time that the system did not have a control feedback loop to assure 50-50 traction control, and that the rear could have more than the published 50% traction limit. The goal was to use my control system experience, to inform interested MS6 owners how their MS6 worked.

Other background info is included on post 129.

Deldran, if you bothered to read the posts, you would understand that Phate had answered my last post, and I was simply replying to him about that reply, with related info. Get a life!
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 Old 10-06-2014, 08:21 AM   #136
 
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Congrats, you still don't need to post in threads acting like you know everything and what phate is doing is incorrect. phate has done more for this platform than most will ever do. Your know it all attitude and telling a very well established member of this community that he is doing it wrong, is extremely disrespectful

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 Old 10-06-2014, 08:32 AM   #137
 
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He politely told me where I was wrong! I understand you are a follower of his, and it would help if you could itemize where I actually said he was wrong.
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 Old 10-06-2014, 08:33 AM   #138
 
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Your not out right saying it your being extremely passive aggressive

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 Old 10-06-2014, 08:54 AM   #139
 
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Sure Dude, I'm done with you.
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 Old 10-06-2014, 09:01 AM   #140
 
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Ok hopefully your done with this thread to. Peace

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 Old 10-06-2014, 01:08 PM   #141
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Aw you guys

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 Old 10-16-2014, 08:13 PM   #142
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Back to important things for a moment. I've already updated the OP with this info:


Bump Steer Profiles!!!






Pics of the setup:











For this, I used a laser level that projects a vertical line away from the wheel surface [don't worry, sketches and even a video included below]. I had the wheel off and set it on top of the rotor. I thought this would be closer to the axis of toe rotation than the wheel face. The problem with this is that there is fore-aft wheel movement during bump travel that you have to account for when projecting onto another surface - read: the wheel center migrates forward or backward during vertical wheel movement (bump/droop). Projecting the laser onto a second surface apart from the car would require taking this movement of the laser level into account, but that's a lot of work.

So, to take care of that variable, I projected the beam onto a mirror and reflected it back onto a ruler I attached just below the laser level. With this, the projected beam and measuring stick move together, so only the rotation of the laser level via toe change will alter the projected position on the ruler. [Note: Even though I know it's not completely accurate, I'm making an assumption that the laser level travels on a completely vertical trajectory through bump travel to make the data collection and calculations simpler - scrub is not accounted for.] Now, because we can assume the mirror is a flat plane, we can simply measure the distance from the level to the mirror and the mirror to the ruler. The sum of this distance is the long leg of a right triangle. As the toe angle changes, the projected line moves along the ruler and we now have the measure of the short leg of a triangle measuring from the start position and the current position.

It's a simple calculation using the arctan and we have the angle. Take these measurements at different points in bump travel (I did every 1/2") and we can easily see how toe changes through bump - aka bump steer. If you want to, for whatever reason, convert these back to "toe inches", you just multiply the tire radius (1/2 height) by the tangent of the angle.

Sketch of Setup

Sketch of Calculations

Remember to work in degrees for this stuff on your calculator. Or, if you really want to work in radians, more power to you.

If you would like to see this setup in action, check out this video.



So, you can draw your own conclusions from the charts, but here's mine from an autocrosser's perspective:

I set the car's ride height not knowing bump steer profiles, and I set it up to be a minimum of 3" of bump travel to max bump. So, I'm essentially only looking at the last 3" of bump travel from full bump, and operating in the first 1-2" of that range for typical peak cornering loads.

The rear: not great. The outside rear tire that's experiencing cornering load is steering the opposite way that I want the car to go. That's true for my current set up during the first 2" of bump...the last 1" of bump travel moves to toe out, but we aren't operating in that region. Raising the car makes this worse. Lowering the car is out of the question since I need the bump travel for actual bumps.
Solutions: give the car some static toe out so the toe will be nearly 0 at cornering loads. Alter some "things" to start getting toe out earlier in bump travel...


The front: A better situation than the rear. Setting the car up 3" away from max bump travel wasn't totally ideal up here. Hindsight is 20/20, right? The first 1.5" of bump travel is good in that it goes toe out rather than toe in (thinking about the outside/loaded tire) . That means it just needs more steering input as the car rolls in a corner, rather than turning more into the corner by itself requiring constant correction.
Solutions: Raise the car just a bit.

The car is staying as-is for the rest of this season since we only have two weekends left. This winter will bring a few changes, and will be corner balanced at different ride heights next season taking this info into account.
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 Old 10-18-2014, 10:59 AM   #143
 
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Originally Posted by phate View Post
Back to important things for a moment.
amen!

It's a simple calculation using the arctan and we have the angle. Take these measurements at different points in bump travel (I did every 1/2") and we can easily see how toe changes through bump - aka bump steer. If you want to, for whatever reason, convert these back to "toe inches", you just multiply the tire radius (1/2 height) by the tangent of the angle.

Remember to work in degrees for this stuff on your calculator. Or, if you really want to work in radians, more power to you.
Great post and analysis. I agree with using degrees for anything related to toe / toe-in. Once you get into inches, the ?where? becomes an issue:

1) from wheel center to tire OD --- what you refered to here (=radius)

2) from rear of tire to front of tire --- what I have measured, and what Hunter uses

3) rear to front of tire, on a 28.6" optional size --- Hunter machines

The first two methods are easy to realistically visualize. The last comes into play when a Hunter alignment was done, with no input of actual tire diameter. This issue is mostly when reading an alignment sheet that has inches or mm's for the toe measurments, and no degrees. From Hunter Engineering:

Originally Posted by Hunter Eng'g
Toe measurements are always measured as degrees, but can be displayed either as angular or distance measurements. To display toe as an angle, select the units of degrees or degrees and minutes. To display toe as a distance, select the units of inches, millimeters, inches @ reference diameter, or millimeters @ reference diameter.

When toe is displayed as a distance, it refers to the difference in track width between the
trailing and leading edges of the tires or wheels. The critical question is, At what diameter of tire or wheel is this distance measured? A larger diameter means a greater distance for a given angle. If the units are inches or millimeters, the diameter is assumed to be 28.648 inches, thus providing a simple conversion of 2 degrees of toe equals 1 inch for toe (or 25.4 millimeter of toe). If the units are inches @ reference diameter or millimeters @ reference diameter, the system uses the reference diameter that is entered on the Vehicle specifications primary screen.

NOTE: Domestically, the units of inches @ reference diameter are used primarily by the heavy truck industry. The units of millimeters @ reference diameter are used primarily in
Europe.

http://huntereng.com.br/suporte/3850T_V11.pdf
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 Old 10-18-2014, 09:18 PM   #144
 
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Clever idea on the mirrors... I bought a laser for suspension measurement but I hadn't connected the dots as to how to make it work yet. I will steal this idea Also I need a garage/driveway to measure it.

If you haven't already- do you know whether you car goes full bump @ AutoX turns in front? (Mine doesn't with GC springs). If you're not reaching that point taper/reversal point. IMO there's not much you can do about the slope of that line, but it keeping it as linear as possible is probably best.

EDIT:
This-
Solutions: give the car some static toe out so the toe will be nearly 0 at cornering loads. Alter some "things" to start getting toe out earlier in bump travel..
I would do carefully... I know it's been tried in subbie forum community and most people did NOT approve. I usually run some toe out, but there is a definite sweet spot, depending on a complex combination of weight management, surface traction (big deal with toe), and how/when you turn in. When it's worked successfully: you get early rotation, then the rear grips and stabilizes which is great. The other side of that equation is too much rotation and a spin. I found it to be safe to use small amounts of rear toe- however, that was stock springs. My rear wheels aren't driven though...

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 Old 10-19-2014, 07:14 PM   #145
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The car doesn't get to full bump in steady state turning. I don't think I've felt it go full bump at all, actually. I'm not so worried about the front, it's an easy fix of just raising the car if it needs it.

The rear is where the trouble lies. I already have an idea that might tweak things enough to solve the bump steer without inducing much more bind. It's even legal, lol.

I'll write more this week about the spring change once results are posted and I can double check times. We autocrossed the car both yesterday and today with the new springs. Today the car was a different animal and I'm pretty sure it was faster overall, AND easier to drive fast.
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 Old 10-20-2014, 03:20 PM   #146
 
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Originally Posted by phate View Post
The rear is where the trouble lies. I already have an idea that might tweak things enough to solve the bump steer without inducing much more bind. It's even legal, lol.


Originally Posted by phate View Post
I'll write more this week about the spring change once results are posted and I can double check times. We autocrossed the car both yesterday and today with the new springs. Today the car was a different animal and I'm pretty sure it was faster overall, AND easier to drive fast.
On Saturday afternoon (after prepping some BBQ ribs for Sunday), I had a vague feeling I was supposed to do something this weekend, then I checked the CCSCC calendar.
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 Old 10-20-2014, 05:15 PM   #147
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Originally Posted by zenit View Post




On Saturday afternoon (after prepping some BBQ ribs for Sunday), I had a vague feeling I was supposed to do something this weekend, then I checked the CCSCC calendar.

Ha! Oh well. We have one event left in November. The trophies in November are always CCSCC hoodies if that entices you at all!

I checked my usual "measuring sticks" from the event, and none of them are working right hahaha. One was on street tires, another in a different car, and my main competition went from 275 wide Hoosier A6's to 315 wide A6's They went on to set the fastest time of the day, lol. I think they'll be even faster after getting comfortable with them and tweaking their setup to maximize potential.

Even though I was only .9s behind them and I was 6th overall Sunday out of 74 (19th overall on Saturday with 84 drivers, bleh), I think I'll really have to work next season to best them. I'll likely be on 255 wide RS3's which I'm hoping will be worth >1s over the current, nearly dead, nearly bald NT05's. The rest will have to be made up for with driver mod and a few more tweaks to the car. I think it can be done. For my wallet's sake, I hope so - I don't want to run rcomps.




So, about the spring change. Saturday I had the rear bar on the softer setting with the 700's, and it was similar to the setup with 600's and stiffer rear bar. Overall, I was driving like crap but still wishing for more rear bias. For Sunday, I set the bar to the stiffer setting and it made a nice difference. The back end was drifting out just a little bit through the longer corners if you backed off the gas a bit and planted itself when throttle was applied. It was beautiful. The slalom this event was tighter by ~12' per cone, so much slower than usual. I was really working to bring the back end around but we weren't carrying enough speed through there to unsettle the rear much. In the areas where I could power out of a turn, I was able to get a bit of power on over steer but it usually wasn't much. Overall, very controllable over steer that was mostly helpful.

Where I'm headed now: I have the stiffest OTS rear spring available, and the WL bar is on the stiffest setting without any room to make it stiffer...The front bar is not perpendicular to the axis of the shock, which should be making the bar seem stiffer than it would be if it were perpendicular. It's not a huge angle, but it's a free adjustment at this point. The end links are too long, but I have a set of shorter end link tubes already made. I'm going to set it up so that it is perpendicular and see how the car reacts. If it helps, I'll probably pull the bar and add a row of holes in the blade to make it adjustable. If I'm remembering correctly, there is enough room to add holes near the end of the bar, making it softer. [That might happen sooner, we have a month until the next autox and I might feel like doing it between now and then.]

If that is making improvements and I run out of adjustment range, I think the non-speed 6 OE front bar is 23mm, vs the speed 6's 24mm front bar. @KevinK2;, can you confirm this? I've searched for quite a while and am pretty sure this is true.

Another option is to remove a front end link and effectively run it with no front bar at all...




Edit: Over the weekend, an entire set of rear control arms was delivered I'm going to measure these and start looking for bushings that will work for us.
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 Old 10-20-2014, 05:52 PM   #148
 
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Correct- FSB bumped from 23 to 24 mm
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 Old 10-20-2014, 06:04 PM   #149
 
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There's not much room on the OE FSB to play, but you could probably get another hole in there. Not sure if it will do any good tho, it'll be very close to the original, and due to the bend it wouldn't really change the math much...

Sorry for crappy pics- I finally got around to swapping out the LCA's & tie rod ends this past weekend tho, so they were handy
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 Old 10-21-2014, 12:18 PM   #150
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Originally Posted by phate View Post

The rear: not great. The outside rear tire that's experiencing cornering load is steering the opposite way that I want the car to go. That's true for my current set up during the first 2" of bump...the last 1" of bump travel moves to toe out, but we aren't operating in that region. Raising the car makes this worse. Lowering the car is out of the question since I need the bump travel for actual bumps.
Solutions: give the car some static toe out so the toe will be nearly 0 at cornering loads. Alter some "things" to start getting toe out earlier in bump travel...

.
I don't want to question your measuring methodology, but I think I have to.
I have a very hard time accepting that the 6 toes out when the rear goes up. or from bump to droop. That creates a very pretty dangerous snap oversteer situation when you lift off the throttle mid corner (trailing throttle oversteer). No modern cars have suspension geometries designed that way. Whether street cars or race cars, toeing out when the ass of the car goes up when you lift of the throttle is not something anyone designs on purpose.

When the rear goes down toe should go out.
When the rear goes up toe should go in.
That's pretty much standard for all cars. Race or street.

You sure there isn't something you need to take into consideration due to the mirrors? like reversing your angles or something?
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 Old 10-21-2014, 12:30 PM   #151
 
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Originally Posted by phate View Post
@Tomas I'm pretty sure he's right. AFAIK, the MS6's rear is pretty similar to our control blade type of setup. The saving grace of that feature is that if you have a static rear "0" toe alignment, even as the toe goes "out" as the ass end goes up, the total toe is still very close to 0.

Now if you run something like 1/4" rear toe out, and the rear end goes up- that's different. Lemme tell you about that
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 Old 10-21-2014, 12:43 PM   #152
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Just double checked my numbers and and I am certain the behavior I've described is correct.

Edit, I can describe how I know this better later today. I still have the original data sets.
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 Old 10-21-2014, 02:00 PM   #153
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Originally Posted by zenit View Post
@Tomas I'm pretty sure he's right. AFAIK, the MS6's rear is pretty similar to our control blade type of setup. The saving grace of that feature is that if you have a static rear "0" toe alignment, even as the toe goes "out" as the ass end goes up, the total toe is still very close to 0.

Now if you run something like 1/4" rear toe out, and the rear end goes up- that's different. Lemme tell you about that
Do you know for fact that the control blade on the 3 creates toe out when the rear lifts? I haven't measured it, but I don't think that's the case. If it were, you wouldn't just get snap oversteer, but the ass of the car would wabble all over the place under hard braking. Same as the 6.
Same as on any multi link rear suspension, I maintain that the basic design calls for toe in when in droop, and toe out when in bump from static ride height.

I'd have to read up more on it to find cases where the opposite might be true. But I doubt it.

I found a good ilustration of this on the interwebz.

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 Old 10-21-2014, 03:41 PM   #154
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Here's my concept and specifics of what I measured. Please double check my thinking.



Here's the setup:


^Note the scale reading 0"->12" from the rear of the car to the front of the car.

If you take a top view approach, it looks like this, initially:


If the car goes toe in, it would look like this (exaggerated, of course):


If the current reading on the ruler is greater than the last ruler reading, it means that it has moved toe in. If you went from a low wheel height to a higher wheel height (moving in a compression/bump motion), then it is moving toe in through bump.

Looking at my original data set, I measured from full droop through full bump using fender:wheel center measures. Notice the toe figures are increasing for the first part, then begin decreasing as we get towards full bump. I actually did this twice, because the jack slipped out from under the control arm.



Don't mind the chart on the right. I was just sketching and it doesn't apply.
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 Old 10-21-2014, 06:00 PM   #155
 
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Originally Posted by Tomas View Post
Do you know for fact that the control blade on the 3 creates toe out when the rear lifts?
Lemme see if I can bother some NATOR folks and borrow a driveway. I can definitely get this data.
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 Old 10-22-2014, 06:37 AM   #156
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Originally Posted by phate View Post



If the current reading on the ruler is greater than the last ruler reading, it means that it has moved toe in. If you went from a low wheel height to a higher wheel height (moving in a compression/bump motion), then it is moving toe in through bump.
Ok. I think I know where the problem is.
Phate you are correct in how you interpret the reading on the ruler.
If the the number is higher on the ruler after having gone up or down then that equates into toe in. However, you are assuming the distance between the hub (lazer) and the mirror stays constant through the droop to bump motion. The distance between the lazer and the mirror will be smallest when the lower control arm is on a horizontal level. When you lift or drop the hub then that distance will increase and that will increase the reading on the ruler. In other words, the distance between the mirror and the laser changes as the wheel goes up and down. When the wheel (laser) comes closer to the mirror then reading on the ruler will decrease. When the wheel moves away from the mirror then the reading on the ruler will increase.


Please see rainbow math below for moar gheyness.

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 Old 10-22-2014, 07:01 AM   #157
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Yep, I put that I was ignoring lateral wheel movement up in the original bump steer post. I would estimate it to be no more than 1" from max to min, but let's say it's 2". That makes it a 76" leg of the long triangle at max, throwing off my figures by a maximum of .037°...That's a 5.7% error, and I don't think that movement is anywhere near that much. [Edit: I'm placing the laser on the top of the rotor, so only ~6" from the center of the hub. That lateral movement will be less than the lateral movement at the contact patch.]

I also don't think it's enough lateral movement to actually alter the movement I've described. It just skews my calculations a bit.

@Tomas; I edited that a couple times just in case you caught it early. I'll leave it be, now ♥
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Last edited by phate; 10-22-2014 at 07:11 AM.
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 Old 10-22-2014, 07:52 AM   #158
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Well, I haven't used Pythagoras since I started masturbating. And I suck at math.
So if you say that's what the error % is then that's what it is.
I am still suspicious of the results however. As mentioned, the car would be pretty unstable if the rear toe /wheel travel characteristics were the way your charts show it.
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 Old 10-22-2014, 12:51 PM   #159
 
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I've never gone to the trouble of measuring myself, as I told Clint awhile ago when we talked about this, but I've always assumed the 3 toes IN under compression because it shares its "control blade" rear setup with the Focus and it was generally accepted as the case with that car when I was active in that community, so it doesn't surprise me that the 6 does as well.

The "passive rear steer" effect would get pretty sketchy at high speeds if it were the opposite...
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 Old 10-23-2014, 10:04 AM   #160
 
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Originally Posted by phate View Post
Even though I was only .9s behind them and I was 6th overall Sunday out of 74 (19th overall on Saturday with 84 drivers, bleh), I think I'll really have to work next season to best them. I'll likely be on 255 wide RS3's which I'm hoping will be worth >1s over the current, nearly dead, nearly bald NT05's. The rest will have to be made up for with driver mod and a few more tweaks to the car. I think it can be done. For my wallet's sake, I hope so - I don't want to run rcomps.
If the competition is on R-Comp tires, I think that gives them an edge on you. I only have experience on the bigger road-race tracks, and they were super sticky ... after a run, I could dig out a chunk of the soft rubber with my thumb nail. Worth several seconds there. You would need ones that don't require lots of heat up.

So, about the spring change. Saturday I had the rear bar on the softer setting with the 700's, and it was similar to the setup with 600's and stiffer rear bar. Overall, I was driving like crap but still wishing for more rear bias. For Sunday, I set the bar to the stiffer setting and it made a nice difference. The back end was drifting out just a little bit through the longer corners if you backed off the gas a bit and planted itself when throttle was applied. It was beautiful. The slalom this event was tighter by ~12' per cone, so much slower than usual. I was really working to bring the back end around but we weren't carrying enough speed through there to unsettle the rear much. In the areas where I could power out of a turn, I was able to get a bit of power on over steer but it usually wasn't much. Overall, very controllable over steer that was mostly helpful.

... If that is making improvements and I run out of adjustment range, I think the non-speed 6 OE front bar is 23mm, vs the speed 6's 24mm front bar. @KevinK2;, can you confirm this? I've searched for quite a while and am pretty sure this is true.

Another option is to remove a front end link and effectively run it with no front bar at all...
I do believe you are right about FSB being interchangeable. Racing Beat impies this:

Racingbeat Mazda-6/MS6/Sway-Bars

Wekk before race day, it looks like you could uncouple just one end of the FSB endlink, and tie it off, to check what no FSB is about. You will find a lot of lean, perhaps making the bump-toe change worse.

If you can find a CS 25mm rear bar, and add a "stiff" hole position to it, that would give you a 1mm stiffer bar (~17% stiffer), vs the whiteline. Prothane makes a low profile bushing kit for that size, in case axle boot clearance is an issue.

.
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Current Fleet: 04 Mazda6, 93 Rx7 TT, 76 Triumph 750 Trident

Tracked Cars: 68 Triumph GT6 (~full race prep'd), 81 Porsche 924 Turbo, 93 Rx7 twin turbo
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