Coilovers: anyone try flat ride + front sway?

[IamFODI]

Looking at Öhlins R&T with Swift springs. 100% street setup for now, with Michelin PS4S in the stock sizes. Looking to increase agility, responsiveness, etc. without big NVH increases or problematic limit behavior.

Default spring rates are 342/684. I'm thinking of going 228/799 for flat ride (roughly the same % increase front and rear) with appropriate damper re-valving, and adding a Dinan front sway bar to get the front roll stiffness back.

Lots of E46 folks seem to love flat ride but I haven't found any feedback from E9x people. Any thoughts?

[tdott]

Originally Posted by IamFODI

Default spring rates are 383/685. I'm thinking of going 228/799 for flat ride (roughly the same % increase front and rear) with appropriate damper re-valving, and adding a Dinan front sway bar to get the front roll stiffness back.

When I was looking into it, it was recommended I go 400/1300.

Didn't end up going with the re-valve service, I went with a set of 3 ways instead.

[IamFODI]

Originally Posted by tdott

When I was looking into it, it was recommended I go 400/1300.

Holy smokes!

400 in front looks like 2 Hz or just above. That’s a bit high for me but I guess it makes sense. 1300 looks insane in the rear though.

[tdott]

Originally Posted by IamFODI

400 in front looks like 2 Hz or just above. That’s a bit high for me but I guess it makes sense. 1300 looks insane in the rear though.

Not my calculations but this was provided for the rates:
"1.9 Hz front, 2.0 Hz rear, for about 5% rear (Flat Ride) bias which will make the car more like it was from the factory, but with a more 'GT' ride and handling balance."

[IamFODI]

Originally Posted by tdott

Not my calculations but this was provided for the rates:
"1.9 Hz front, 2.0 Hz rear, for about 5% rear (Flat Ride) bias which will make the car more like it was from the factory, but with a more 'GT' ride and handling balance."

Interesting. Either they have the wrong motion ratios, or they know something I don't...

[M3SQRD]

I had to run a much higher front rate relative to rear rate on my e46 M3 (with GC F/R sway bars) to control the loss of front camber. It started out as a brand new street car and within 2 years it became a dedicated track car. Two-way Motons with spring rates > 800 lbf/in. The e92 M3 camber curve is slightly better than the e46 M3 but still needs a higher front rate relative to the rear to help control camber loss (F8x is an improvement but still needs a decent amount of negative camber and spring rate). I owned two e92 M3s at the same time with the same suspension setup except for spring rates. I found 400/650 (400/700 is recommended by many different suspension companies/race shops) to be a great street setup whereas the 2nd M3 had 700/1000 for a dual-purpose track-street setup.

I don’t know of any off-the-shelf suspensions that come with rates close to what your suggesting. The stock suspension rides the front bump stops so the soft front spring rate can add confusion because its effective rate is higher. Calculating ride frequencies is a good way to come up with an initial set of rates on a new chassis (e9x has been around for quite a while now ) but from my 30+ years of setting up suspensions I’ve always ended up with very different rates once things have been sorted out. I think you’d need a massive front sway bar to get the sharp turn-in response you’re looking for but then I wouldn’t be surprised if you encountered mid-corner steady-state oversteer. Springs are relatively cheap so start where you want and then adjust from there.

[IamFODI]

Thanks for your feedback, M3SQRD!

Originally Posted by M3SQRD

The stock suspension rides the front bump stops so the soft front spring rate can add confusion because its effective rate is higher.

Do you know of any measurements of the front bump stops? It'd be useful to know how much spring rate it's really contributing.

IIRC -- and please don't quote anyone but me on this -- Barry at 3DM guessed that in most cases the bump stop isn't contributing enough to make the effective spring rate much higher than 200 lbs/in. Do you think it's more than that?

Originally Posted by M3SQRD

I think you’d need a massive front sway bar to get the sharp turn-in response you’re looking for but then I wouldn’t be surprised if you encountered mid-corner steady-state oversteer.

I'd love it if you could help me understand this. In my mind, the front sway bar would not only sharpen the front end but also fight the oversteer. Is this incorrect?

[M3SQRD]

Originally Posted by IamFODI

Thanks for your feedback, M3SQRD!

Do you know of any measurements of the front bump stops? It'd be useful to know how much spring rate it's really contributing.

IIRC -- and please don't quote anyone but me on this -- Barry at 3DM guessed that in most cases the bump stop isn't contributing enough to make the effective spring rate much higher than 200 lbs/in. Do you think it's more than that?

I'd love it if you could help me understand this. In my mind, the front sway bar would not only sharpen the front end but also fight the oversteer. Is this incorrect?

I believe I have a stock e92 M3 bump stop still sitting around...

I know with lowering springs, people switch to an e36 M3 bump stop and shave the e92 strut guide by 0.35” to yield about ~0.6” of travel. I believe the stock setup has around the same amount of travel. So any suspension travel > 0.6” means you’re riding on the bump stop. Not sure what the stock bump stop rate is but IIRC it’s somewhere in the middle of an aftermarket soft and stiff bump stop.

My comment about a massive sway bar to get sharp turn in is because of the soft front spring rate. However, you have such a large spring rate delta front-rear that the sway bar effective spring rate won’t be enough to balance out the relatively high rear spring rate so the car would then start to transition to oversteer. With the rates I’m running I’ve dialed out almost all understeer and your F/R spring ratio is much lower so I’d expect the balance to be biased toward oversteer.

[Richbot]

A lot of your *perception* of ride comes from the rearend - You can REALLY crank up front rates (as seen in almost all coilover setups that double or triple the stock front rate) without makign the car too terribly jittery

So if ride is a priority, pay a LOT more attention to getting your rear dampers set up than adding a bunch of rear spring - Agree with the 650 rear recommendation above.

I am still chasing the ride quality my MCS setup had and most of what I am chasing is the super-good control the rear shocks offered, the one-hit, no-memory rearend is the hardest thing to get right, one-hit-and-done starts to feel pretty harsh with springs that don't budge

The E9x doesn't experience the same camber loss as the E46, the solution is no longer to just not let the suspension move up front, so I don't think adding bar up front will introduce much oversteer, at least not mroe than you can easily tune around with alignment and tire pressure, if you're also using a stiffer than stock spring and damper with itnernal bumpstops

On *stock* springs, adding a front bar helps dial *out* some understeer, bceause of that camber loss he's talking abuot above (And it helps stay off the bumpstop for longer). This was my experience with stock dampers and stock springs, and with the MCS + stock springs; I ran the bar on full stiff (on staggered hoosiers) to get the balance where I wanted it.

But now on my car, which has a Sachs ~320lb/in front coilover on it right now, that's no longer the case and more bar = more understeer, and I now have the Dinan bar on full soft to get the balance where I want it. So many variables, but that's been my experience

[IamFODI]

Originally Posted by M3SQRD

I believe I have a stock e92 M3 bump stop still sitting around...

Would be awesome if we could get some measurements on that! I'm sure it's been done but I couldn't find numbers or a graph anywhere.

Originally Posted by M3SQRD

My comment about a massive sway bar to get sharp turn in is because of the soft front spring rate. However, you have such a large spring rate delta front-rear that the sway bar effective spring rate won’t be enough to balance out the relatively high rear spring rate so the car would then start to transition to oversteer. With the rates I’m running I’ve dialed out almost all understeer and your F/R spring ratio is much lower so I’d expect the balance to be biased toward oversteer.

Makes sense.

Is this about total roll stiffness (springs + sways) across each axle? The numbers I'm running suggest that 228/799 springs with a Dinan front bar can net more roll stiffness in front than in rear (from a stockish front/rear balance to more front-biased, depending on the setting). Sounds like you're less than sanguine about calculated results though, yeah?

[IamFODI]

Originally Posted by Richbot

On *stock* springs, adding a front bar helps dial *out* some understeer, bceause of that camber loss he's talking abuot above (And it helps stay off the bumpstop for longer). This was my experience with stock dampers and stock springs, and with the MCS + stock springs; I ran the bar on full stiff (on staggered hoosiers) to get the balance where I wanted it.

But now on my car, which has a Sachs ~320lb/in front coilover on it right now, that's no longer the case and more bar = more understeer, and I now have the Dinan bar on full soft to get the balance where I want it. So many variables, but that's been my experience

That's an interesting dynamic. Thanks for laying it out.

Whatever setup I go with, I'm hoping that staying at or very near stock non-Comp ride height will help avoid camber loss.

I remember reading your Sachs suspension kit commentary. Are you still on the stock rear spring? Does the car pitch any more or less than it used to, even if it's tolerable?

[derbo]

I too am curious.

That said I have 400/700 with MCS 2WNR and very happy with it on the street. I don't have a lot of track time with it yet so hopefully that changes in the coming year after all this mess dies down.

[derbo]

Bringing this back from the dead.

Starting doing some math.

Front 325lb || Rear 900 is roughly 1.86Hz, 1.85Hz, roughly slightly pitch.
Add a front sway Eibach sway bar 29mm tubular, brings the front roll couple (FRC) to about 76.2%


Reference Stock:
Front 160 || Rear 550 lbs/in , 1.3Hz || 1.45Hz , 1.11 Flat Ride
26.5mm tubular front , FRC = 75.6%


IamFODI I know you ended up with Ohlins. Did you ever want to revisit flat ride + big front sway?

I'm thinking about buying a 325lb 6" spring to test as I am now on 600/900 setup and I don't like how it pitches on the street bumps.


Current setup:

Front 600 || Rear 900
Ride Frequency 2.52Hz , 1.85Hz , 0.73 Pitch ride
FRC = 76.6%

[IamFODI]

Originally Posted by derbo

IamFODI I know you ended up with Ohlins. Did you ever want to revisit flat ride + big front sway?

Short answer: Yes, but not enough to actually try it.


Long answer:

AFAICT, if I were to try this, I'd be among the first. For various reasons, I'm not the guy and this isn't the car for that.

If I went with softer front springs to get flat ride, they'd have to be MUCH softer than the out-of-the-box Öhlins rates I'm running. If my experience is any indication, I'd be crashing into the bump stops constantly without a much different bump stop (something along the lines of the very long and progressive stock one) and/or a lot more damper stroke (ideally with a longer damper body). Basically I'd need new damper bodies and bump stops, likely custom.

I didn't want to try much stiffer rears because they'd have to be well over 800 lbs/in and/or true coilovers, which for some reason almost no one ever seems to run on the street. I don't understand why, but I've learned that if everyone or no one is doing something, there's probably a reason whether I understand it or not. That doesn't mean the reason is good, but it does mean I had to anticipate more challenges than I'm currently willing to address.

I also saw some evidence from Obioban's experience that was not encouraging for me. As a preface, he went flat ride on his E46 M3 and was blown away by how good it was. To call him satisfied is an understatement. He calls it the best mod he's ever done, which is really saying something given the number of mods under his belt and how great his car is in every way right now. With that in mind, two things gave me pause:

1. By the time he settled on an anti-roll bar setup that got him to a relatively neutral handling balance, he ended up with a much higher calculated FRC% than stock. In other words, if he had just matched stock FRC% with his stiffer-than-stock springs, he'd have ended up with a ton of oversteer. This made me not want to try flat ride with stiffer-than-stock springs unless I knew there was a front ARB out there that could get my FRC% much higher than stock if needed. When I ran calcs on 228f/799r springs, the stiffest front bar I could find for the E9x M3 (Dinan on position 3) was barely enough to get stock-like FRC%. And with stiffer springs than those, the front ARB would have to be even stiffer. Either way, I needed to know there was a front ARB that was much stiffer than the Dinan one, and I couldn't find one.

2. His front ARB -- again, the one he needed to neutralize the oversteer -- was apparently stiff enough to rip out one of the mounting brackets. So, I thought, even if I could find a front ARB stiff enough for my purposes, it might require parts of the car to be reinforced, and I didn't feel like taking that chance.

Please note, I am not claiming to be authoritative here. This is all the hypothesizing of an amateur, and I'm probably wrong about a lot of it. I'm not saying flat ride can't work on this platform or is a bad idea or anything. The point here is that, with the meager tools at my disposal, I don't see good enough odds of success that I’d bet my own time and resources on it. I'm sure it could work; someone better than me just has to figure it out.

If you're interested in my extended opinions on my setup, I wrote a big post here.

[derbo]

Originally Posted by IamFODI

Short answer: Yes, but not enough to actually try it.


Long answer:

AFAICT, if I were to try this, I'd be among the first. For various reasons, I'm not the guy for that, and this isn't the car for that.

If I went with softer front springs to get flat ride, they'd have to be MUCH softer than the stock Öhlins rates I'm running. If my experience is any indication, I'd be in the bump stops constantly without a much different bump stop (something along the lines of the very long and progressive stock one) and/or a LOT more damper stroke (ideally with a longer damper body). Basically I'd need new damper bodies and bump stops, likely custom.

I didn't want to try much stiffer rears because they'd have to be well over 800 lbs/in and/or true coilovers, which for some reason almost no one ever seems to run on the street. I don't understand why, but I've learned that if everyone or no one is doing something, there's probably a reason. That doesn't mean the reason is good, but it did mean I had to anticipate more challenges than I'm currently willing to address.

I also saw some evidence from Obioban's experience that was not encouraging for me. For the record, he went flat ride on his E46 M3 and was blown away by how good it was. To call him satisfied is an understatement. He calls it the best mod he's ever done, which is really saying something given the number of mods under his belt and how great his car is in every way right now. With that in mind, two things gave me pause:

1. By the time he settled on an anti-roll bar setup that got him to a relatively neutral handling balance, he ended up with a much higher calculated FRC% than stock. In other words, if he had just matched stock FRC% with his stiffer-than-stock springs, he'd have ended up with a ton of oversteer. This made me not want to try flat ride with stiffer-than-stock springs unless I knew there was a front ARB out there that could get my FRC% much higher than stock if needed. When I ran calcs on 228f/799r springs, the stiffest front bar I could find for the E9x M3 (Dinan on position 3) was barely enough to get stock FRC%. And with stiffer springs than those, the front ARB would have to be even stiffer. Either way, I needed to see a front ARB that was much stiffer than the Dinan one, and I couldn't.

2. His front ARB -- again, the one he needed to neutralize his car's handling -- was apparently big enough to rip out one of the mounting brackets. So, I thought, even if I could find a front ARB big enough for my purposes, it might require parts of the car to be reinforced, and I didn't feel like jumping into that pool.

I am not saying any of this is authoritative. It's all the hypothesizing of an amateur, and I'm probably wrong about a lot of it. I'm not saying flat ride can't work on this platform or is a bad idea or anything. The point here is that, with the tools I have, I don't see good enough odds of success that I'd want to bet on it. I'm sure it could work; someone better than me just has to figure it out.

If you're interested in my extended opinions on my setup, I wrote a big post here.

Thanks for that. Interesting as when I use a 32mm Hollow Dinan, my FRC was well over 80% with some of the flat ride combos I was looking at.

What numbers are you getting for stock FRC? Do they match what I wrote?

Reference Stock:
Front 160lbs/in || Rear 550 lbs/in , 1.3Hz || 1.45Hz , 1.11 Flat Ride
26.5mm tubular front , FRC = 75.6%

My current setup:
Front 600lbs/in || Rear 900lbs/in , 2.52Hz || 1.85Hz , 0.73 Pitch
26.5mm tubular front , FRC = 76.6%

Proposed attempt setup:
Front 325lbs/in || Rear 900lbs/in , 1.86Hz || 1.85Hz , 0.99 Pitch
29mm Eibach tubular front , FRC = 76.2%

[IamFODI]

Originally Posted by derbo

Thanks for that. Interesting as when I use a 32mm Hollow Dinan, my FRC was well over 80% with some of the flat ride combos I was looking at.

What numbers are you getting for stock FRC? Do they match what I wrote?

Reference Stock:
Front 160lbs/in || Rear 550 lbs/in , 1.3Hz || 1.45Hz , 1.11 Flat Ride
26.5mm tubular front , FRC = 75.6%

My current setup:
Front 600lbs/in || Rear 900lbs/in , 2.52Hz || 1.85Hz , 0.73 Pitch
26.5mm tubular front , FRC = 76.6%

Proposed attempt setup:
Front 325lbs/in || Rear 900lbs/in , 1.86Hz || 1.85Hz , 0.99 Pitch
29mm Eibach tubular front , FRC = 76.2%

I was getting FRC% numbers in the mid-50s with the stock setup.

Guessing the calcs you're using are estimating ARB rates based on diameter and tubular vs. solid. Is that correct? If so, maybe that accounts for some of the difference.

I found an Eibach PDF that gave actual measurements for the stock ARB rates: 194 lbs/in front, 112 lbs/in rear. Attached it here. Dinan says their front ARB is 50% to 90% stiffer than stock, so 368.6 lbs/in max. Those are the values I used.

Again, not saying I did everything right.

[derbo]

Originally Posted by IamFODI

I was getting FRC% numbers in the mid-50s with the stock setup.

Guessing the calcs you're using are estimating ARB rates based on diameter and tubular vs. solid. Is that correct? If so, maybe that accounts for some of the difference.

I found an Eibach PDF that gave actual measurements for the stock ARB rates: 194 lbs/in front, 112 lbs/in rear. Attached it here. Dinan says their front ARB is 50% to 90% stiffer than stock, so 368.6 lbs/in max. Those are the values I used.

Again, not saying I did everything right.

No worries. I'm not sure I am doing everything right either. I do find it hard to believe that the FRC is below 68% if the stock E46M3 is that.

https://www.fatcatmotorsports.com/FC..._M3_Online.htm

A few friends and I extrapolated FCM's spreadsheet and adjusted all the values that were required in blue for our own chassis purposes. I've been working on the E90M3 one this past week.

Davisca455 was kind enough to get measurements of the swaybar based on this image:


Rear:
A = 8.3125"
B = 29.00"
C = 13.00"
D = .900"


Front:
A = 9.625"
B = 23.50"
C = 11.50"
D = 1.05"


Of course I dont have the exact measurements of the Dinan or Eibach sways as most likely B and C are different by a bit.

[tsk94]

Originally Posted by IamFODI

I was getting FRC% numbers in the mid-50s with the stock setup.

Guessing the calcs you're using are estimating ARB rates based on diameter and tubular vs. solid. Is that correct? If so, maybe that accounts for some of the difference.

I found an Eibach PDF that gave actual measurements for the stock ARB rates: 194 lbs/in front, 112 lbs/in rear. Attached it here. Dinan says their front ARB is 50% to 90% stiffer than stock, so 368.6 lbs/in max. Those are the values I used.

Again, not saying I did everything right.

That's correct for the stock setup. Usually mid 50's. But what it doesn't take into account is the bump stop activation and it's affect on spring rate with the stock springs.

[derbo]

Originally Posted by tsk94

That's correct for the stock setup. Usually mid 50's. But what it doesn't take into account is the bump stop activation and it's affect on spring rate with the stock springs.

I'm getting conflicting answers when using FCM spreadsheet for stock.

Hmm. What is the formulas you guys are using?

[tsk94]

Originally Posted by derbo

I'm getting conflicting answers when using FCM spreadsheet for stock.

Hmm. What is the formulas you guys are using?

I could send you my spreadsheet, I don't use the FCM one though. Didn't find it worked well.

The stock number will be low due to the ratio of front to rear spring rate, but it doesn't take into account the bump stops, which on the stock suspension activate very early on and bump up the spring rate big time.

[IamFODI]

Originally Posted by tsk94

That's correct for the stock setup. Usually mid 50's. But what it doesn't take into account is the bump stop activation and it's affect on spring rate with the stock springs.

Yup. Something an aftermarket setup likely won't have, which sets the bar (pun intended) for FRC% even higher.

[tsk94]

The FCM spreadsheet isn't good.

Use this one: https://robrobinette.com/Suspension_Spreadsheet.htm

Much easier and more intuitive. The only thing you need to know is the sway bar rate. Which for this car is easy to find out.