MS6 Suspension Data & DIY Bilstein Coilovers

[KevinK2]

Originally Posted by KevinK2 We know the rate is based on active coils, and with so few active coils in these high rate springs, especially the 800's, the change in last coil supported at the flat ground spring ends, based on load, appears to give the initial progressive rate ...

Originally Posted by Phate With the 800's, you can literally see the inactive section move further into the first coil (from each end), which is likely the cause of the 'progressive' spring rate.

Looks like you're saying the same thing, so we agree here.



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[KevinK2]

Originally Posted by phate The ride isn't bad at all. The 600's were super comfy just cruising around town, and the 700's aren't much worse. With the 850F/700R, it's about the same ride quality (maybe slightly better) as a stock sprung, stock shock 1st gen MS3. I've been so impressed by these dampers since I got them back. Shaikh just posted this video, I thought it was pretty interesting.

It appears, as indicated by the video, that the dampers are the center point for making your suspension so well behaved on the street with relatively stiff springs. The video referenced another FCM video where he consulted for an Audi owner, and he tested having no dampers in the car, with very interesting results. When consulting on ME problems, I often used limit analysis, which is what this is.
FCM Test Drive with No Dampers

Originally Posted by BAT-man His videos support a theory I've been a proponent of for quite some time - one should not be afraid of body roll, within reason ....

I agree. But to get an idea of what works, you can google images of SCCA National results, and focus on ~similar sedans, like BMW. The roll transient is related to delayed response. Based on some of Phates videos, inspite of his near FTD lap times, there may be some 10ths to be saved with less roll.

Note I have consistently cautioned against excessive roll bar stiffness, that kills the independence of the independent suspension. On my tracked Rx7, I ran moderately stiff bars with otherwise stock suspension, and when jacking up one side of the car, there was near zero droop on the lifted wheel, and little compression of the loaded wheel. Lucky the Summit Point track was mostly smooth. Stock bars went back on after the last HPDE.


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[BAT-man]

Originally Posted by KevinK2 It appears, as indicated by the video, that the dampers are the center point for making your suspension so well behaved on the street with relatively stiff springs. The video referenced another FCM video where he consulted for an Audi owner, and he tested having no dampers in the car, with very interesting results. When consulting on ME problems, I often used limit analysis, which is what this is. FCM Test Drive with No Dampers I agree. But to get an idea of what works, you can google images of SCCA National results, and focus on ~similar sedans, like BMW. The roll transient is related to delayed response. Based on some of Phates videos, inspite of his near FTD lap times, there may be some 10ths to be saved with less roll. Note I have consistently cautioned against excessive roll bar stiffness, that kills the independence of the independent suspension. On my tracked Rx7, I ran moderately stiff bars with otherwise stock suspension, and when jacking up one side of the car, there was near zero droop on the lifted wheel, and little compression of the loaded wheel. Lucky the Summit Point track was mostly smooth. Stock bars went back on after the last HPDE. .

Yup. I've taken off the rear sway on my FC and run a stock front, and that's in spite of using it as a part time drift car.

...On July 4th I even take the front one off

[phate]

We autocrossed both Saturday and Sunday this past weekend. Car setup:

850F/700R springs, stock front bar with poly bushings, my rear bar on full soft, 255/40/17 RS3 V2's.

Saturday was spent figuring out tire pressures and learning how the RS3's behaved on concrete. Overall, both Johanna and I liked them quite a bit more than the Rivals. We ended up with 37/37.5psi front/rear. That gave us just a bit of oversteer if we asked for it, but nothing crazy and it was completely manageable. The RS3's may not have as much overall pure lateral grip compared to the Rivals, but they are much better at combined cornering and braking or acceleration. We realized that a little too late on Saturday, so neither of us did great - we ended up 3rd and 4th out of 5 (ouch!) and 18th and 23rd out of 104, overall.

We came into Sunday armed with this knowledge and knew we had to push the car and ourselves to have any chance of keeping up. We ran 3rd heat (last one), and right out of the gate we were on par with the fastest times of the day, thus far. Things were looking up. I was trying to trail brake more than I ever have and think I did ok with it. I was getting on the gas HARD coming out of turns and for the first time experienced some inside front wheel spin. I need to address this, somehow. It was enough to end up 1st and 2nd in class (out of 10) and 6th and 14th, overall out of 105 drivers.

My fastest:

YouTube Short

YouTube Short

Johanna's fastest:

YouTube Short

YouTube Short

Setup thoughts:

1) Poly bushings in the front end helped the turn in oversteer we were having the last time we were on concrete
2) The car could use a little more rear bias. It was still understeering in the big sweepers.




That concludes the season for us. Awesome event, fun course, lots of good competition. And that brings us to this winter. There are a few projects I've been thinking about, so I've started a list:

1) chop and flare for the 275's - this is the top priority
2) Address the front wheel spin - not sure about this yet
3) Lighten the car a bit - exhaust and lightweight battery are the main sources

[ItsNox]

Man those runs looked fast!

Have you considered getting a 51r sized battery and putting it in the trunk?

Edit: of course you have. you built your own rear sway bar lol

[phate]

Originally Posted by ItsNox Man those runs looked fast! Have you considered getting a 51r sized battery and putting it in the trunk? Edit: of course you have. you built your own rear sway bar lol

I'm looking for something even lighter

[MSP611]

like this clint:

Braille Battery B2015K, Braille Advanced AGM Lightweight Racing Batteries | Braille Battery

this is the lightest ive seen without sacrificing too many CCA's

they do have a 11.5lb one tho but low CCA's

[xfeejayx]

Out of curiosity since you rode along, where would you put my car with respect to bias?

I was a little blown away how it behaved this weekend; neutral but had drift mode when wanted. Obviously the grip is a whole different level. Didn't really feel any under steer.

Sent from my Nexus 5 using Tapatalk

[Code Monkey]

You can buy/make 1-2 lbs batteries now. A 6-lbs Braille will also work, although you would have to disconnect it and put it on a tender if you do not use your car every day. At this weight it does not make any sense to relocate to the trunk as the cable and bracket will weight more than the battery itself.

[phate]

Originally Posted by MSP611 like this clint: Braille Battery B2015K, Braille Advanced AGM Lightweight Racing Batteries | Braille Battery this is the lightest ive seen without sacrificing too many CCA's they do have a 11.5lb one tho but low CCA's

Originally Posted by Code Monkey You can buy/make 1-2 lbs batteries now. A 6-lbs Braille will also work, although you would have to disconnect it and put it on a tender if you do not use your car every day. At this weight it does not make any sense to relocate to the trunk as the cable and bracket will weight more than the battery itself.

Thanks. I've seen Braille's get used fairly often in race cars and they're a consideration. Lithium batteries are a lighter option, and I've just discovered LiFePO4 and LiPO setups that weigh in at just a couple pounds. I need to do more reading about them, as some batteries require a minimum charging voltage or they can be damaged very quickly.

Originally Posted by xfeejayx Out of curiosity since you rode along, where would you put my car with respect to bias? I was a little blown away how it behaved this weekend; neutral but had drift mode when wanted. Obviously the grip is a whole different level. Didn't really feel any under steer. Sent from my Nexus 5 using Tapatalk

I usually can't tell from riding shotgun unless it's major over or understeer. You typically drive within the limits of the car, so I didn't notice. I'd have to drive it some time

My only suggestion is to forget the idea of 'neutral' handling, and try to figure out why one end isn't sliding at least a little bit. Play with steering input in sweepers to see if the car can turn sharper or if you're really on the limit of front end grip, or give it a bit more gas to see if it understeers, or lift just a bit to see if it oversteers. Also factor in tire pressure differentials front to rear - I interpret significantly higher rear pressures as a fix for a pushy car. It moves you away from where the tire achieves max grip, and it makes the rear of the car stiffer making it seem more rear biased than it would be if the tire was at 'max grip pressure'.

[Code Monkey]

You could make something like this for autox and switch to a larger battery for daily duty.

[phate]

Some pictures from the weekend:


^The bumper brackets finally gave up completely. Luckily they'll get tied together with the future flares



My favorite picture, Johanna coming into the finish a little sideways and full throttle




@xfeejayx; about to capsize:

[MSP611]

Originally Posted by Code Monkey You can buy/make 1-2 lbs batteries now. A 6-lbs Braille will also work, although you would have to disconnect it and put it on a tender if you do not use your car every day. At this weight it does not make any sense to relocate to the trunk as the cable and bracket will weight more than the battery itself.

isnt this more of the situation where u want more room upfront in the engine bay just for ease of maintenance (possibly for BT guys) and to balance out the weight distro' a lil?

[xfeejayx]

Originally Posted by phate Some pictures from the weekend: ^The bumper brackets finally gave up completely. Luckily they'll get tied together with the future flares My favorite picture, Johanna coming into the finish a little sideways and full throttle @xfeejayx; about to capsize:

I could probably measure how much camber the front left needs off that pic.

Sent from my Nexus 5 using Tapatalk

[phate]

Lightweight battery thread:

Shedding Weight - Ultra Light LiFePO4 Batteries





In other news on shedding weight. Last time I was driving up to autocross, the car suddenly got louder Got there and checked it out and found this dangling by the last hanger, so I pulled it off...



This exhaust is from the previous owner and it was pretty cobbled together. Flowmaster chambered mufflers...Anywho, I weighed this one muffler and it weighs 11lb, so I'm guessing I'll drop ~25lb getting rid of them and a few feet of piping.

The car isn't all that loud, the last videos I posted are without that muffler, so I'm thinking I'll do a straight dump to the ground just below the rear seat.






The last source of weight savings for this winter will be an AC system removal. Compressor, condenser, and lines up to the firewall. I'm not allowed to remove any of the HVAC system in the cabin, so it's staying. I'll add more as I order the belt and pulley for this project.

[Code Monkey]

A pulley? Just relocate the alternator to the front. Shorter belt = a few ounces saved + you can shorten the alternator wires, good for another ounce or two.

[phate]

Alternator can't be relocated, per the rules.

[zenit]

Imma leave this here:

[Code Monkey]

^ Same suspension, the guy on the left clocked in at 400 lbs though.

[KevinK2]

Originally Posted by Code Monkey ^ Same suspension, the guy on the left clocked in at 400 lbs though.

Perhaps same rate springs, 850/700, but looks like a higher CG. Phate's custom rear bar is much stiffer than any upgraded oem bar, partly due to hard plastic vs poly bushings and low MR on oem rear. I pushed the custom rear bar concept in December last year, when the idea of using rear bump stops to add roll resistance did not work out:

Custom Rear Bar, post 235
"It's tough trying to stiffen the rear springs with bump stops that have velocity based properties, when a larger sway bar would work best. I designed a bar for rear swing axles, under the axles, but with a transverse leaf spring so there was much more area to work with. If the rules allow it, I'd make sure there is no way to do this, allowing some loss of ground clearance."

Custom Rear Bar post 236
"If this were possible, the motion ratio could be much improved allowing a smaller dia bar that is much stiffer than oem. And with two sets of mounting holes at the lever arms, the arm length could have stiff and stiffer positions."

Bar Rates at Wheel: (Phate)

WL Soft Setting: 43 lb/in
WL Stiff Setting: 52 lb/in

New Bar Soft: 72 lb/in
New Bar Stiff: 190 lb/in

Also, Phate upgraded suspension bushings with either hard poly whiteline bushings, or soft poly oem type 1-piece molded bushings from Russian contacts. Not sure if xfeejayx did the same.



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[Nliiitend1]

[phate]

A few irons in the fire...First, the lightweight battery project is well under way. Everything has been shipped and I should have parts next week.



Second, fender flares! CanyonRider over at mazda6club used flares from jdmflares.com second time around. His first version were of unknown origin and ~2" front and rear, then he replaced them with the 'wide zg flares'.

His first version of flares starts here. Second version starts here.

I considered some from the same site, but I don't think fiberglass would stand up to even 1 good cone hit. I generally liked the dimensions of the first set he had (the second set is really huge) so I went looking for something similar. For all things rice, eBay is the place to go. I found some ABS flares with a 2" lip from seller jdmff (in case anyone needs this in the future).

Some pictures from their ad:

Pic 1
Pic 2
Pic 3 (dimensions)

They're coming from Russia, so they'll probably be here in January, haha.




Lastly, I've been thinking about the minor front inner wheel spin I was getting at the last autocross. I'm not really sure what I'm going to do, but I have some ideas. [Other ideas welcome!]

1) Since I won't have to worry about rubbing fenders anymore, I can afford to lower the car just a bit more, which should reduce weight transfer a bit.

2) I've also said the car needed more rear stiffness, so we'll bump up rear bar stiffness just a touch relative to where it's at now - that should put a bit more load on the inner front.

3) Lower the front upper perches to allow more droop travel

4) Add rear bump stops that only engage in roll with pitch (cornering and acceleration).

5) Stop trying to accelerate so hard out of corners

[KevinK2]

Originally Posted by phate Lastly, I've been thinking about the minor front inner wheel spin I was getting at the last autocross. I'm not really sure what I'm going to do, but I have some ideas. [Other ideas welcome!] 1) Since I won't have to worry about rubbing fenders anymore, I can afford to lower the car just a bit more, which should reduce weight transfer a bit. 2) I've also said the car needed more rear stiffness, so we'll bump up rear bar stiffness just a touch relative to where it's at now - that should put a bit more load on the inner front. 3) Lower the front upper perches to allow more droop travel 4) Add rear bump stops that only engage in roll with pitch (cornering and acceleration). 5) Stop trying to accelerate so hard out of corners

Couple thoughts:

Canyon Racer's LSD

That front hood is heavy and mounted high, not sure if you reduced weight there yet? CR removed the frame structure .. not sure how much weight that saved.


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[MS3johanna]

Found you some new friends to go along with those JDM fender flares!!

[zenit]

You missed this friend, flare-hanna.

[phate]

Originally Posted by KevinK2 Couple thoughts: Canyon Racer's LSD That front hood is heavy and mounted high, not sure if you reduced weight there yet? CR removed the frame structure .. not sure how much weight that saved. .

Availability is the big one. Since nothing is marketed specifically for the Speed6, I don't know of anyone that has tried getting one. There's some speculation that the MS3 LSD would work, but I don't think it's been proven.


I can't do a whole lot to save weight in this class. No body/frame work other than fenders (but only up to the vertical plane of the wheel mounting surface when the wheels are pointed straight ahead)

[KevinK2]

Originally Posted by MS3johanna Found you some new friends to go along with those JDM fender flares!

Isn't the rear tuck on that 2nd pic breathtaking !! At least there is no chance of hydroplaning in the rain.



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[MS3johanna]

Originally Posted by zenit You missed this friend, flare-hanna.

I totes had this image url copied too!! But, I decided to go with the Protege instead. Thanks! more friends=more better!

[Mazdazilla6]

Regarding the inner tire slip.

1. Aren't you moving to a larger front tire? (might eliminate or mitigate the slip)

2. Is it legal to put air bags in the springs? Might be possible to pressurize them so they don't affect the spring rates normally but when you're coming out of corners they could help keep the front tires down by jacking up the spring rate when the spring gets to a certain point in travel. (Kind of like your bump stop idea, I think)

3. I was always under the impression that a front LSD on an AWD vehicle induces really bad understeer. Am I wrong?

[phate]

Originally Posted by Mazdazilla6 Regarding the inner tire slip. 1. Aren't you moving to a larger front tire? (might eliminate or mitigate the slip) 2. Is it legal to put air bags in the springs? Might be possible to pressurize them so they don't affect the spring rates normally but when you're coming out of corners they could help keep the front tires down by jacking up the spring rate when the spring gets to a certain point in travel. (Kind of like your bump stop idea, I think) 3. I was always under the impression that a front LSD on an AWD vehicle induces really bad understeer. Am I wrong?

Yep, good call. We're moving from a 25" tire to a 26" tire. That will help some by reducing thrust force a smidge. Another benefit is that they are likely going to be MUCH stiffer than any tire I've run before. Those will both be helpful.

Air bags are legal, but not something I want to work with. Bump stops are simpler and you can control stiffness/engagement point much easier since there are so many different ones offered. Early on in the thread I put together a list of ~20 bump stops from Eibach that could work in the 6.

The understeer thing...sort of. How they engage and transfer torque is really important for them to be beneficial. Here's a good read about using them for autocross: Autocross.dsm.org - DSM Specific Autocross Tech Articles - AWD Differential Tech

[Tomas]

I am fairly certain the MS3 F-LSD will work on the 6.
Thought about swapping it in while I had the 6 tranny out. Decided against it.
You can hais for cheap if you want.
And yes I troll threads to sell my shit.

[KevinK2]

Originally Posted by phate ... About front LSD:" The understeer thing...sort of. How they engage and transfer torque is really important for them to be beneficial. Here's a good read about using them for autocross: Autocross.dsm.org - DSM Specific Autocross Tech Articles - AWD Differential Tech"

Very good article. As simple as these things are, the Phantom Grip kits have proven to be effective in most cases. Not sure if they will work on the MS6. As with clutch type LSD's, the degree of lock is based on friction, and using extra GM or Redline LSD diff lube can tune (loosen) the degree of lock. I used this to loosen the lock on the rear Torson diff on my tracked FD-Rx7. Stopped the back end from coming around when pulling out onto a road with wet conditions.

Phantom Grip Kit

Redline Limited Slip Friction Modifier

As you said, a MS3 LSD may work.



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[KevinK2]

Originally Posted by phate That's exactly the idea. I need to incorporate this into my spreadsheet, now. The numbers I come up with for my current setup, where I typically run ~35psi with the rears being slightly higher: Front 850lb/in spring @ .73 MR -- 453lb/in WR 205lb/in bar @ .73 MR -- 109lb/in, but doubled in roll, so 218lb/in WR so 671lb/in wheel rate 1590lb/in tire (typically around 35psi). Combined rate of 472lb/in. Rear 700lb/in @ .57 MR -- 227lb/in WR 72lb/in @ 1.0 MR -- 72lb/in, but doubled in roll, so 144lb/in WR so 371lb/in wheel rate 1590lb/in tire (typically around 35psi). Combined rate of 301lb/in. Those are interesting if you go a little further with an assumption that the front and rear track widths are equal. I showed a page or so back that playing with track width up to 1" on one end of the car isn't a huge influence on roll bias, so the .2" difference we're ignoring is mostly negligible. Once you make that assumption, you can directly use the wheel rates to calculate roll bias. Without Tire Spring Rate Front WR + Rear WR = 671 + 371 = 1042lb/in Front Roll Bias = 671/1042 = 64.4% With Tire Spring Rate Front WR + Rear WR = 472 + 301 = 773lb/in Front Roll Bias = 472/773 = 61.1% Comparing to my 58.1% front weight bias, it shows the car might be much closer to neutral than I thought, when I wasn't including tire spring rate.

When you run the numbers with a 26mm Steeda front bar (24mm oem), does the rear bar adjustment allow the same target roll stiffness bias?

Knowing you lose almost 50% in bar stiffness due to poly bushings, vs the Puhn calculated rate, it's possible to make Nylon or Delrin split bushings for the front oem bar. One guy's design:



Or the JBR aluminum brackets for the MS3 may be a starting point.

Originally Posted by Tomas I have the racingbeat FSB. Barely noticeable change from stock. Car still rolls like a mofo. Not like the Hotchkiss FSB on the MS3 which really tightens down the front end.

I think the RB bar is a M3 design, at 28.6mm, it's only 2.6mm more than MS3 stock, 10% dia increase. But for a M3, it's a 36% dia increase. I think ...



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[phate]

Originally Posted by KevinK2 When you run the numbers with a 26mm Steeda front bar (24mm oem), does the rear bar adjustment allow the same target roll stiffness bias? Knowing you lose almost 50% in bar stiffness due to poly bushings, vs the Puhn calculated rate, it's possible to make Nylon or Delrin split bushings for the front oem bar. One guy's design: http://www.members.shaw.ca/kremer/swaybar2.jpg Or the JBR aluminum brackets for the MS3 may be a starting point.

This reminds me: I did a quick test of the Steeda bar a while back but never posted the numbers. I did it in ~20lb increments (I was short on time) so I didn't test the lower increments to watch initial rates.

Steeda Front Sway Bar - 385lb/in

I didn't measure bar deflection at the bushings this time, so I can't correct for bushing deflection.

I come up with a theoretical bench rate of 570lb/in, so it's a reduction of ~32%. The poly bushings supplied with the Steeda bar are significantly harder than the Whiteline bushings for their rear bar. They were very difficult to open the split to slide over the bar, so I just slid them on from the end. The Whiteline bushings are pliable enough that I can split them without a problem.


To answer your question: Yes, I have enough rear bar to compensate back to my current roll stiffness distribution. Even with solid bushings on the front bar so it is near the 570lb/in rate, I still have enough to just barely get more rear bias than I currently have.

[zenit]

Originally Posted by KevinK2 ... it's possible to make Nylon or Delrin split bushings for the front oem bar. One guy's design: .

If you any insight in how to implement bushing like this, let me know.
I was under the impression that delrin at least required semi-tight locational clearance type fit when used as a bushing. The MS3 stock bars that I've measured run pretty large diameter tolerances (+- 0.2mm) across the width of the bar.

I've never thought of a good way to make the two work together.

[KevinK2]

Originally Posted by zenit If you any insight in how to implement bushing like this, let me know. I was under the impression that delrin at least required semi-tight locational clearance type fit when used as a bushing. The MS3 stock bars that I've measured run pretty large diameter tolerances (+- 0.2mm) across the width of the bar. I've never thought of a good way to make the two work together.

Good question.

You don't need to make the bushing bore compatible across the width of the bar, just 2 places. Large dia variations occur at the bend points for obvious reasons. I just measured a stock rear bar off a my Mazda rx7, at the bushing location, and it was +/- .0015", vs your +/- .008" along the length of the bar. The example I showed was not off a machined bar, like Phate's custom fabricated rear bar.
http://www.members.shaw.ca/kremer/RSRProject.htm

I used split aluminum bar for an oem front bar bushings on one tracked car, with no trace of looseness or wear. I do sand off the coating where the bushings are.

I'd be interested in the diameter tolerance at your bushing locations.




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[zenit]

Originally Posted by KevinK2 ... I'd be interested in the diameter tolerance at your bushing locations. ... .

I'll have to pull my bar to measure, unless someone in NATOR IL has one lying around. I was originally collected the data after I first bought the car, and I was surprised just how large the tolerances were across the total of the bar, including the bushing surface- I didn't sand the down the paint though.

This what your flares need to look like @phate;

[KevinK2]

First, some mechanical properties. Note that there are many versions of Nylon and Acetal (Dupont's Delrin), including special low friction and wear versions with either chemical lube additives ( Delrin 500CL) or solids like Teflon ( Delrin 100AF). I have samples of both. "Nylatron" is a slippery version of Nylon, with solids of a chemical lube.
Nylatron family of Nylon bearing materials .
Mechanical Properties of Various Bearing Materials

From a design standpoint, you would want to reduce the contact width of the bushing, vs oem rubber and poly upgrades. In my own aluminum example, the metal bushing was 3/4" wide at contact with a 1" dia oem bar. The narrow contact reduces the effect of misalignment between the two support points on the bar ( perfect would be coaxial centerlines, hard to get with a cold formed bar shape). The narrow contact also increases the contact pressure at the plastic bushing, which typically reduces the coefficient of friction for these materials.

The theoretical stiffness of the sway bar, with infinitely stiff bushings, is approximated by a formula derived by Fred Puhn, an engineer and race car driver. From his book "how to make your car handle" :
Sway bar rate formula, Fred Puhn

Note the width dimension is to the imaginary intersection points. No dimensions refer to the bushing locations.

The softening effect on rate, due to poly and oem bushings, include how thick the bushing is, beyond the bar diameter, and the hardness of the bushing. It is also related to the ratio of the distance between the two bushings, vs the distance between the link holes at the end of the bar. If those two spans are about equal, then the softening effect is minimal. The smaller that Ratio of spans, the more softening occurs.




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[silvapain]

Originally Posted by zenit I'll have to pull my bar to measure, unless someone in NATOR IL has one lying around. I was originally collected the data after I first bought the car, and I was surprised just how large the tolerances were across the total of the bar, including the bushing surface- I didn't sand the down the paint though. This what your flares need to look like @phate;

I have my stock rear anti roll bar in my garage.

[Nliiitend1]

Originally Posted by silvapain I have my stock rear anti roll bar in my garage.

As do I.