Ground control bmw e9x complete street/sport kit

[ConceptE92]

Hello BimmerPost Family!

Please delete if not allowed. I posted this under suspension as well, but figured later that this might be a better place.

I have done some searching and have tried to contact Ground Control themselves, however, I cannot get a solid answer almost by no one with some solid explanation.

I have previously owned a 2012 E92 M3 with the coilover conversion kit from GC, however, now I am looking to purchase the Complete Street Kit for a different 2011 E92 M3 that I own. Having said that, I am looking to find out the spring rate that some of you have ran that have owned this kit.

I previously lived in FL where the roads were pretty flat, and I believe at the time I ran a 400F/700R spring rate on the conversion kit which was perfectly fine, nothing to worry about. I took the car to the track about 4-5 times a year around Homestead MotorSpeedway and Palm Beach and no complaints, note that the again the flat surface didn't bother.

Now that I live in GA, I have done some track days here at Road Atlanta with my E46 M3. On this particular car the Spring Rates are 600/900 and the car feels great, however, this car is a lot lighter (3,100 lbs) vs the E92 M3.

It has been 5 years since I have owned the conversion kit on my 2012 E92 M3 which I no longer own, so what I remember may have felt fine back then, however, I am looking to get the right kit w the right spring rates around this time.

What do you recommend?
What spring rates do you run at Road Atlanta and other tracks that have more elevation change to them?
I understand that higher spring rates doesn't necessary improve grip, matter of fact opposite in extreme cases depending on pavement, however, I am trying to dial in the correct numbers. In terms of tires, I am running RE71 as the tire, 275/35/18.

Please let me know what you recommend and what your experience has been. I am also open to other suspension setup, however, I do have a budget I would like to stick of $2K.

Looking forward to your response,

Thank you,


AR

[tsk94]

500/800 or 600/900 is pretty common setup for a light duty track car that's still going to be driven on the road. I think either of those would work well for you. Go the stiffer option for more track performance and softer for more civilized street use. Those Koni's can also only be valved to handle so stiff of a spring. I've heard ~700lb/in is the limit for those single adjustable ones before they need more work done to them, which would cost more. The rears being divorced mean the shock don't see the same spring rate as the spring itself, so ~900 in the back is still fine.

Suspension geometry between the E46 and E92 is vastly different, so you can't really compare spring rates between the two. I think around the 600/900 range would be more then sufficient for the amount you're tracking and what tires you plan to run.

[ConceptE92]

Originally Posted by tsk94

500/800 or 600/900 is pretty common setup for a light duty track car that's still going to be driven on the road. I think either of those would work well for you. Go the stiffer option for more track performance and softer for more civilized street use. Those Koni's can also only be valved to handle so stiff of a spring. I've heard ~700lb/in is the limit for those single adjustable ones before they need more work done to them, which would cost more. The rears being divorced mean the shock don't see the same spring rate as the spring itself, so ~900 in the back is still fine.

Suspension geometry between the E46 and E92 is vastly different, so you can't really compare spring rates between the two. I think around the 600/900 range would be more then sufficient for the amount you're tracking and what tires you plan to run.

Exactly what I was after! I will probably end up going the 600/900 route and report back once installed. Thanks for your feed back!