e46 M3 suspension setup, or how to not downgrade your car with suspension mods

[Tbonem3]

I should have said that it'll depend on strut. I have MCS and can run anything I want, bottom perch height-wise - plenty of adjustment. On my Bilstein b6 with GC conversion, 7" was 325lb so at 400lb, I would look for 6.25" like tck vvs or a 6" with extended travel like eibach's xt.

I run tck 400lb which is only in 60mm & it says 6.5" but really is 6.25" tall.

[r4dr]

IMO, using stock mounts defeats a very useful feature of aftermarket coilovers/plates for us - reducing ride height for free through reduction of stack height in camber plates from GC, Vorshlag, TMS and probably others.

If you just want stock like height (14"+) then you'll have plenty of travel I suppose.

There's a caveat on this with the Ohlins, isn't there? Hence the need for those 3DM spacers when you shorten the stack height with aftermarket camber plates. I was always under the impression that the R&T struts were designed specifically for stock top mounts, leading to the ride height issues without the strut spacers.

[Tbonem3]

Ah ok. I'm not up to speed on the ohlins and that spacer issue. I want as much travel as possible at a pretty low height of like 13.25" so maybe someone like me wouldn't even bother with the spacer.

Is the concern, without a spacer, that the car would sit too low with aftermarket plates?

Couldn't you just move the bottom perch upwards to compensate? Droop will be very short, I imagine.

[Obioban]

There's a caveat on this with the Ohlins, isn't there? Hence the need for those 3DM spacers when you shorten the stack height with aftermarket camber plates. I was always under the impression that the R&T struts were designed specifically for stock top mounts, leading to the ride height issues without the strut spacers.

The strut spacer is the result of the setup being developed with european kingpins and US kingpins being different.

[Obioban]

Ah ok. I'm not up to speed on the ohlins and that spacer issue. I want as much travel as possible at a pretty low height of like 13.25" so maybe someone like me wouldn't even bother with the spacer.

Is the concern, without a spacer, that the car would sit too low with aftermarket plates?

Couldn't you just move the bottom perch upwards to compensate? Droop will be very short, I imagine.

The problem is that the Ohlins have very little total travel-- so to have them function properly, you pretty much MUST optimize ride height for bump/droop travel.

Without the strut spacers on a US spec car, you have to be lower than the suspension geometry is good for. Similarly any camber plate that increases bump travel too much does the same.

[Tbonem3]

Ok so then it does seem that they engineered them for the taller/thicker stock mounts :/

Too bad stock mounts are as expensive as camber plates these days!

[jet_dogg]

The strut spacer is the result of the setup being developed with european kingpins and US kingpins being different.

Euro and US m3s use the same kingpins.

[Obioban]

Euro and US m3s use the same kingpins.

Hmm, seems like you’re right.

well, something is different and I forget what, it seems. Whatever it is, the result is that the US cars need the strut spacer and the euro cars don’t.

[Thoglan]

Hmm, seems like you’re right.

well, something is different and I forget what, it seems. Whatever it is, the result is that the US cars need the strut spacer and the euro cars don’t.

Yeah weird, Euro car here and with ohlins and GC street camber plates I sit at about 13.25" hub to fender with the right bump/droop without the use of the spacer. When using the spacer it put me further outside of the range. Not sure what else would be different in the geometry though.

[r4dr]

Hmm, seems like you’re right.

well, something is different and I forget what, it seems. Whatever it is, the result is that the US cars need the strut spacer and the euro cars don’t.

Is this true for US cars regardless whether it's using stock top hats or camber plates?

[Chas3n]

For those on a budget, my current setup according to the calculator and butt dyno is flat ride.

Bilstein B4
Eibach pro kit springs
Hotchkis F/R sways medium front, soft rear

Great comfort, bumps even with Hankook v12 (awful sidewalls) feel smooth, car turns in very well, and isnt unsettled at motion changes/apex bumps. Couldnt be happier, as it nearly feels my like old MCS setup. Ride height is fixed, but low enough where it looks OE+ but not low enough where its compromising the control arms/bushings.

[Cronenberged]

I went with a build directly built by FCM.

H&R street coilvers
450lb 6" f spring
800lbs 6" r spring
GC weighted jacks
GC front Sway bar stiffest setting
OE rear sway bar.

Will give some feed back as soon I get everything in and on the car.

[duracellttu]

For those on a budget, my current setup according to the calculator and butt dyno is flat ride.

Bilstein B4
Eibach pro kit springs
Hotchkis F/R sways medium front, soft rear

Great comfort, bumps even with Hankook v12 (awful sidewalls) feel smooth, car turns in very well, and isnt unsettled at motion changes/apex bumps. Couldnt be happier, as it nearly feels my like old MCS setup. Ride height is fixed, but low enough where it looks OE+ but not low enough where its compromising the control arms/bushings.

What are you spring rates? Also, did you measure corner weights?

I went with a build directly built by FCM.

H&R street coilvers
450lb 6" f spring
800lbs 6" r spring
GC weighted jacks
GC front Sway bar stiffest setting
OE rear sway bar.

Will give some feed back as soon I get everything in and on the car.

Also curious if you measured your corner weights before FCM recommended spring rates? Were these spring rates aimed towards a sporty or more race focused setup?

[mrgizmo04]

I went with a build directly built by FCM.

H&R street coilvers
450lb 6" f spring
800lbs 6" r spring
GC weighted jacks
GC front Sway bar stiffest setting
OE rear sway bar.

Will give some feed back as soon I get everything in and on the car.

With those rates it sounds borderline pitchy, and adding GC on full stiff to those front rates sounds very understeery...

Did FCM suggest these rates/bar settings? Are you running heavy aero/splitter to counter?

Sent from my SM-G950U using Tapatalk

[duracellttu]

With those rates it sounds borderline pitchy, and adding GC on full stiff to those front rates sounds very understeery...

Did FCM suggest these rates/bar settings? Are you running heavy aero/splitter to counter?

Sent from my SM-G950U using Tapatalk

Per the spreadsheet, those spring rates give you a 1% flat ride.