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      12-27-2012, 09:05 PM   #27
italyix's Avatar

Drives: '08 E90 M3
Join Date: Dec 2011
Location: Bay Area

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Originally Posted by M3SQRD View Post
Ah, I misread your orig post - I thought 600 was being used in the stock location, and 1200 was being used in the coilover location...

So you are recommending a F/R 500/1200 lbf/in setup for a R spring mounted in the stock location (i.e., control arm mounted)? I do not know of a single person running that spring combo on a street or dual-purpose setup using Motons, Ohlins, JRZ, AST, or MCS dampers - are you running, or did someone recommend, this spring rate combo?

I'm currently running F/R 500/800 on JRZ dampers, and previously 600/800 on Moton dampers, R springs mounted in the stock location for both setups.
After reading the sticky in this section, and I quote: "The solution to the Type Three rear suspension compromise is to convert the rear to coil-over. By putting the coil spring around the damper, the motion ratio goes up from 57% to 83%, drastically reducing the leverage on the subframe. It increases the load on the body where the spring mounts, but the leverage is much less than on the subframe mounts. Also, because the action is more “direct”, the spring rate is much lower. If you want the rear rate to be a good match to a new, higher rate 500# front, then you can use a 600# coil-over spring, delivering a rear wheel rate of just over 400# that will work nicely. To do the same using the stock spring location would call for an unhealthy 1200# spring."

Although the above calculates a rear spring at a little over 400lb, it is actually around 500lb (600*0.83 = 498lb)

This would complement the front 500lb nicely.

Sway bars then can provide more "spring" when you need it (cornering that is)
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