[boony1968]

I'm picking up an '18 M2 with the M Performance Suspension. I intend to autox the car SCCA B Street which means I must run the stock springs. The DA dampers are within the rules provided the ride height is near stock.

So, two questions - Will the stock springs mount correctly on the MPS perches? And, should the valving and adjustment ranges on the MPS dampers play nice with the rates of the stock springs?

[M Fifty]

The fronts will - but not sure about the ride height. There's quite a bit of adjustment though.

The rears will also - but I think they'll be too long by quite some way is you leave the height adjustable perches in there. Even with the MPS rear springs they're pretty much at the limit of adjustment at the specified (lower) ride height, while the stock springs are a couple of inches longer.

But, as the rear springs and dampers are separate, stock rear springs and stock upper mounts will be no problem.

As the 'road' setting for the MPS dampers are in the top third of the adjustment range, backing them off to suit the 30% (?) softer stock springs shouldn't present difficulties.

[boony1968]

Thank you. My biggest concern was the front spring perches. The rears will have to go a complete stock setup anyway, so no issue on that end. Ride height will need to be as close to stock as possible on the front too. From what I read a stock ride height is within the adjustment range even with the (I assume shorter) MPS springs.

[jetbill]

Originally Posted by boony1968

Thank you. My biggest concern was the front spring perches. The rears will have to go a complete stock setup anyway, so no issue on that end. Ride height will need to be as close to stock as possible on the front too. From what I read a stock ride height is within the adjustment range even with the (I assume shorter) MPS springs.

Agreed rear no issue.

Front MPS spring is a bit different at the bottom vs stock I believe. I can take a pic of each for you.

Since the title of the thread is regarding spring changes for the MPS...I wanted to mention I'am currently running 250/800 (1.6 / 1.82 hz calculated ride frequency "flat ride"with 65.3% Nominal FRC) 2.5" linear coil springs with Dinan front sway full stiff and GC plates (F3.5 /R2.0 camber).

Edit: Now on 400/800 both 8" , slight pitch (2.0 / 1.82 hz calculated ride frequency (slight pitch) with 68.2% Nominal FRC during normal driving but 400 seems to hold the car up better.
Ironically @ these rates and close to full soft (C9/R15 & C10/R16) on both compression and rebound the car is super compliant "wife mode", from here I'll add front comp and rear rebound for more rotation
I'll run these rates at Sebring a few weeks from now and Autox and report back, i suspect the out of the box C6/R9 F and C6/R12 R street setting would work ok for Sebring (bumpy) vs the track setting (C4/R7 and C4/10).

[jetbill]

Here ya go
Stock vs. MPS front progressive

[boony1968]

Thanks, looks like it won't work up front. I'll give it a shot. Luckily, I was about to pick up a complete stock suspension from a forum member.

[jetbill]

Originally Posted by boony1968

Thanks, looks like it won't work up front. I'll give it a shot. Luckily, I was about to pick up a complete stock suspension from a forum member.

Maybe Vorshlag can make you a custom lower perch.

http://www.vorshlag.com/forums/showthread.php?p=58767

[boony1968]

I just pulled a front wheel and confirmed your pic. For my class I'll have to put the convert the front back to 100% stock. The stock springs will go back in the rear too but I'll give the adjustables at least one event. Might be better than 100% stock.

[M Fifty]

Maybe if you tried the HAS kit from the M3/4?

[TexasUp]

Originally Posted by boony1968

I just pulled a front wheel and confirmed your pic. For my class I'll have to put the convert the front back to 100% stock. The stock springs will go back in the rear too but I'll give the adjustables at least one event. Might be better than 100% stock.

Hope it works out. If you need to convert back to stock, I'd be interested in the coilovers.

[boony1968]

Originally Posted by M Fifty

Maybe if you tried the HAS kit from the M3/4?

Thanks, but I can't see how that would help. It doesn't seem possible to change the lower mount on the M strut to accept the stock spring.

Originally Posted by TexasUp

Hope it works out. If you need to convert back to stock, I'd be interested in the coilovers.

The rear seems to be at the correct height with the M shocks and stock springs. I'll shoot you a PM if they don't work out and I decide to sell the entire setup.