Suspension by the Numbers - Car Setup How To

[Gandalf]

Have Koni FSD's on Cobb springs, Cobb rear sway, 6 pc chassis brace set, RE-71's in 225/50-16 on 16x8 re-enforced FD wheels, EBC yellow pads, SS lines and ATE blue fluid. Not my first time but not Clint level shit either. A little sarcasm included in my previous post.

 

[Redline]

Have Koni FSD's on Cobb springs, Cobb rear sway, 6 pc chassis brace set, RE-71's in 225/50-16 on 16x8 re-enforced FD wheels, EBC yellow pads, SS lines and ATE blue fluid. Not my first time but not Clint level shit either. A little sarcasm included in my previous post.

Gotta have full coilovers/full adjustability for that Clint-level, corner-balanced, measuring and optimizing everything performance standard, LOL

 

[Gandalf]

I need to replace the FSD's soon but can't afford 2k Coil overs. I'll probably get a set of the Bilsteins.

 

[Redline]

I need to replace the FSD's soon but can't afford 2k Coil overs. I'll probably get a set of the Bilsteins.

I hear ya. I REALLY wanna do some SCCA to join MSM and get the coilovers. But I think I'd have a hard time convincing the wifey on my DD. Being fully bolted, BNR'd, eth'd/meth'd already means she has already accommodated my hobby a lot, LOL. We still cart around our 1-year-old in the back seat all the time, haha
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I need to replace the FSD's soon but can't afford 2k Coil overs. I'll probably get a set of the Bilsteins.

The MSM ones are ~1.6k IIRC, for MSM members. Steal of a deal.

 

[phate]

You lost me at Hello. I don't want to understand your voodoo, just want you to tell me what to buy. Geez.

MS6 if you want to go fast.
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I need to replace the FSD's soon but can't afford 2k Coil overs. I'll probably get a set of the Bilsteins.

The Bils are awesome. @VTMongoose is working on the MS3 Bilstein coilover conversion, so that is an option that allows for upgrade down the road.

 

[VTMongoose]

There may or may not be bilsteins on my car right now in fact...details to come...

I will say to do it properly, did cost me way more than I originally intended. But there will be a lot of flexibility for people who want to do things a little differently, and a little more cheaply. The only real problem is the ride height issue. My setup with the shortest springs I could get raised my car 1/8" in the front with the adjuster all the way down. This is not going to be good for about 99% of people who want the "lowered" look. Personally I am very happy that I was just able to get this shit to fit my car, and at the ride height I want.

 

[461_SS]

That probably because you still have the front stock spring perches attached. I know on the Koni's you lose some "low" adjustment with the perches still attached if I remember. You're also running a helper spring which takes up some room as well as a 7" spring.

Come out to a few AutoX events and I'll show ya how it's done ;-) Sucks I missed the Hershey one. Save that for the end of the season!

 

[VTMongoose]

That probably because you still have the front stock spring perches attached. I know on the Koni's you lose some "low" adjustment with the perches still attached if I remember. You're also running a helper spring which takes up some room as well as a 7" spring.

Yes, running the helper springs was an optional addition by myself because I actually want my springs to stay in place when I jack up the car and not have to guide them into their spots every time I lower the car. Believe me, the problem is not as simple as it appears. I did exclude most of the details in my thread because this has been a months-long process between me and ground control trying to get this sorted. Bottom line, the perch is completely non-removable from the Bilsteins. It is welded in so many places, you would be better off fabricating a new shock body from scratch. Furthermore the perch also sits a lot higher on the Bils than on the Koni's...about an inch or so.

Definitely will be doing as much autocrossing as possible this season.

 

[461_SS]

Yes, running the helper springs was an optional addition by myself because I actually want my springs to stay in place when I jack up the car and not have to guide them into their spots every time I lower the car. Believe me, the problem is not as simple as it appears. I did exclude most of the details in my thread because this has been a months-long process between me and ground control trying to get this sorted. Bottom line, the perch is completely non-removable from the Bilsteins. It is welded in so many places, you would be better off fabricating a new shock body from scratch. Furthermore the perch also sits a lot higher on the Bils than on the Koni's...about an inch or so.

Definitely will be doing as much autocrossing as possible this season.

Are you going to be around this Sunday? Philly SCCA is doing a rust off at Warminster. It would be good for you as you'll get as many runs as you want basically. If so, I'll stop over and help instruct you if you want.

The springs will go back into place as the car goes down without guidance. Never had a problem and my car is up down and up more than I can count during the summer haha. You can just shake the car to get the springs to settle if they don't, but I've never had to do that.

 

[VTMongoose]

Are you going to be around this Sunday? Philly SCCA is doing a rust off at Warminster. It would be good for you as you'll get as many runs as you want basically. If so, I'll stop over and help instruct you if you want.

The springs will go back into place as the car goes down without guidance. Never had a problem and my car is up down and up more than I can count during the summer haha. You can just shake the car to get the springs to settle if they don't, but I've never had to do that.

I would love to come, but I need a new clutch unfortunately (it slips above 350 wtq or so right now) before I hit the dragon. I'll be down swapping that with the Nator AL guys.

I'm surprised you don't have any problems with the springs. The included GC bearings wouldn't seat properly in the OE top hat for me unless I guided them in by hand for some reason. Of course I have the GC camber plates now, so that might be a non-issue.

 

[SavSpeedMS3]

I have been looking at getting a set of H&R springs. I've read a few really good reviews.

 

[Redline]

Been doing tons of research, and came here again, @phate. I have a question regarding this comment you made:

"The big caveat: Ride quality is more a function of the shocks than the spring rates and frequencies. If you have shocks that have ridiculous amounts of high speed damping, the car is going to ride like crap (I'm looking at you...every...budget (and even some expensive) coil over kit out there). As a reference, my MS6 is set up at 2.2 Hz front and ~2.47 Hz rear and the ride quality is decent. It's not uncomfortable except for some weird mid-speed bumps. Sharp bumps get sucked up like you wouldn't believe, and low speed transitions are great. It's all about the shocks."

In your opinion, are OTS Koni Yellows and OTS Bilstein B8s "high quality" shocks in terms of not having, as you said, "ridiculous amounts of high-speed damping"? I ask because I'm leaning toward the GC coilover kit and plan on retaining my front Koni Yellows and rear Bilstein B8s.

Maybe one day if I get a daily beater and can retire the Speed to weekends and tracking/auto-xing fun duty, I could get both sets of dampers revalved to be optimized for the spring rates I settle on. Based on this chart, and assuming 2,200 sprung weight front/1,400 sprung weight rear, I'm leaning towards using the frequency method of spring selection and going with ~430 lbs/in front and ~370 lbs/in rear with a goal of a 1.9/2.1 F/R ride frequency:


This chart assumes a motion ratio of 1, so I think my calculations are correct, but only for the front. But then I see what @VTMongoose did in his thread, here: http://mazdaspeeds.org/index.php?threads/johns-bnr-s3-daily-driver-performance-build.726/ , and I'm concerned that I need to factor in 1.10 for the front 1.28 for the rear? So I should I apply 1.10/1.28 multipliers to my estimated front/rear spring rates to get what I'm going for, ending up with ~410/470?

Sorry for all the questions. I'm reading a ton. I just didn't see you mention any multipliers in your post about figuring spring rate according to frequency, Clint, nor in here http://www.optimumg.com/docs/Springs&Dampers_Tech_Tip_1.pdf in terms of implementing them.

 

[ConeKiller]

This chart assumes a motion ratio of 1, so I think my calculations are correct, but only for the front. But then I see what @VTMongoose did in his thread, here: http://mazdaspeeds.org/index.php?threads/johns-bnr-s3-daily-driver-performance-build.726/ , and I'm concerned that I need to factor in 1.10 for the front 1.28 for the rear? So I should I apply 1.10/1.28 multipliers to my estimated front/rear spring rates to get what I'm going for, ending up with ~410/470?

pretty sure those aren't multipliers, those are divisors. In this application, motion ratios decrease the effective spring rate.

 

[VTMongoose]

@ConeKiller 's motion ratios are spring/wheel. Some equations online use wheel/spring. Make sure you invert appropriately when specified. I found this out when doing my calculations (I was getting weird numbers)

 

[Redline]

@ConeKiller 's motion ratios are spring/wheel. Some equations online use wheel/spring. Make sure you invert appropriately when specified. I found this out when doing my calculations (I was getting weird numbers)

So that would be why the MS Coilovers and KW v3s have spring rates in the 400/290 range? That would make sense to me.

But if you're still on 440/500, wouldn't that feel wonky? Is that what you landed on/stayed with after all (if I'm reading your thread correctly)?

 

[phate]

That chart is misleading - it is not SPRING rate, it is WHEEL rate. That's the effective spring rate at the wheel, after the loss of leverage is factored in. That loss of leverage is from the motion ratio, which is the first thing described in the OP. You need to be able to convert from spring rate to wheel rate through the motion rate, THEN look at everything else. MR's simplify the process and put everything on a level playing field (wheel rate playing field).

OTS coil over kits run a very soft rear spring for who knows why. I think they assume that you will get enough rear bias by going with a gigantic rear bar - which is a pretty good assumption if you just go off of what everyone on the forums does. Realistically, though, the typical aftermarket companies have no idea what frequencies their suspensions will put your car at - call up any of them if you don't believe it.

I've autocrossed MS3's with both the KW V3 and MSM coil overs. I thought both of those cars could use a lot more rear spring. YMMV.
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Sorry for all the questions. I'm reading a ton. I just didn't see you mention any multipliers in your post about figuring spring rate according to frequency, Clint, nor in here http://www.optimumg.com/docs/Springs&Dampers_Tech_Tip_1.pdf in terms of implementing them.

Take a look at the examples I wrote out in the frequency method post. They both work backwards from target rate and sprung mass to get a wheel rate, then back even further to get a required spring rate. Motion ratios

 

[Nliiitend1]

OTS coil over kits run a very soft rear spring for who knows why. I think they assume that you will get enough rear bias by going with a gigantic rear bar - which is a pretty good assumption if you just go off of what everyone on the forums does. Realistically, though, the typical aftermarket companies have no idea what frequencies their suspensions will put your car at - call up any of them if you don't believe it.

I've autocrossed MS3's with both the KW V3 and MSM coil overs. I thought both of those cars could use a lot more rear spring. YMMV.

I think they do it to keep the ride quality more "OEM-like."

Yes, super stiff rear springs certainly look great on paper with this car, but I think with the rear suspenion geometry (with it's built-in "bind") and it's small amount of travel (the OEM bumpstops do as much as the springs in this car to contribute to effective wheel rate, IMO) before jounce bumper engagement, even the softer springs end up getting you to the same place (approaching infinite wheel rate) - they just get the car to do it a little more slowly and allow a small amount of "easy travel" to soak up road bumps and make the car live-able on streets like we have here in Chicago.

I sort of feel like the springs on the 3 are a tender spring in a tender/main setup, with the aforementioned bushing bind and jounce bumper engagement acting as the main spring.

Just my rambling thoughts (that are not in any way backed up by actual measuring or doing any real math) on the matter, anyway.

 

[Redline]

That chart is misleading - it is not SPRING rate, it is WHEEL rate. That's the effective spring rate at the wheel, after the loss of leverage is factored in. That loss of leverage is from the motion ratio, which is the first thing described in the OP. You need to be able to convert from spring rate to wheel rate through the motion rate, THEN look at everything else. MR's simplify the process and put everything on a level playing field (wheel rate playing field).

OTS coil over kits run a very soft rear spring for who knows why. I think they assume that you will get enough rear bias by going with a gigantic rear bar - which is a pretty good assumption if you just go off of what everyone on the forums does. Realistically, though, the typical aftermarket companies have no idea what frequencies their suspensions will put your car at - call up any of them if you don't believe it.

I've autocrossed MS3's with both the KW V3 and MSM coil overs. I thought both of those cars could use a lot more rear spring. YMMV.
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Take a look at the examples I wrote out in the frequency method post. They both work backwards from target rate and sprung mass to get a wheel rate, then back even further to get a required spring rate. Motion ratios

I hear ya. But in that table I posted, if the motion ratio is 1, then it's irrelevant anyways. You multiply (4(pi)^2)(ride frequency^2)(sprung mass)(motion ratio^2). If the motion ratio is 1, 1 squared is still 1. So everything in the formula leading up to that is multiplied by 1, so it's effectively irrelevant, correct? So in cases like this, spring rate:wheel rate would be 1:1 (in other words, the same), if I'm understanding this correctly.

 

[phate]

I hear ya. But in that table I posted, if the motion ratio is 1, then it's irrelevant anyways. You multiply (4(pi)^2)(ride frequency^2)(sprung mass)(motion ratio^2). If the motion ratio is 1, 1 squared is still 1. So everything in the formula leading up to that is multiplied by 1, so it's effectively irrelevant, correct? So in cases like this, spring rate:wheel rate would be 1:1 (in other words, the same), if I'm understanding this correctly.

Seems irrelevant, really. You don't have a 1.0 motion ratio and I don't know of any cars that do - so it's wheel rate. Once you have target frequencies as a design requirement, you work backwards to wheel rate, then further back to spring rate using the motion ratio.

 

[Chemmedic]

Thanks for the excellent info. I have a lot of reading to do.