whats a good spring rate for coilovers?

kingoftarmac · Post by **kingoftarmac** » Wed Feb 01, 2012 7:35 pm

whats a good spring rate for coilovers that are only going to be used for daily driving?

Odometergears · Post by **Odometergears** » Fri Feb 03, 2012 2:36 pm

Million dollar question. I could give you a starting point but then you have to adjust from there. Everything depends on everything. Weight, balance, shocks, tires, rims, swaybars...

I'll give you my set up.

Corner weights:
1018 LF 927 RF
3377 total
719 LR 711 RR

57.6% front
51.2% cross
51.4% left 48.5% right
42.3% rear

I have 600lbs 7 inch 2.5 in the front
450lbs 7 inch 2.5 in rear

17 inch tires. 235's I think. Car is in storage for winter.
21mm front 19mm rear sway bars. Rear is adjustable

Struts and shocks are Bilstein. They were valved for the corner weights of the car.

What I just figured out was the internal bump stops on the front struts are bottoming out so I am not getting a lot of travel in the front. The struts are HD's. One of the differences between HD's and Sports is the travel. Going with the coilovers, I missed the travel calculation. I should have been using sports. I'm sending the struts and shocks back to CA, Bilstein, for adjustment.

Hope this helps. I also added all urethane bushings on the body, motor mounts and suspension.

Pete K · Post by **Pete K** » Mon Feb 06, 2012 8:58 am

This question comes up about every 12 months and there's at least as many opinions as there are posters, usually more!

I agree that it's totally based on every other factor you've got going. My little 520i runs 250lb front, 225 lb rear on 225/50/16s (Toyo Proxes track tires). She only weighs 2700 lbs including me though.

I also run bigger sway bars at 26 and 21 mm.

I've been thinking of going up to 450 lb front and 350 lb rears, but the car and I are currently in different countries.

I've seen a track day special that had 1000 lb springs in it!

Let us know what you end up with.

Cheers

wkohler · Post by **wkohler** » Thu Feb 09, 2012 4:34 am

My only coilover experience is with E28s, but they're similar in the weight distribution, etc. I ran 440 front and 400 rear, but I'd suggest running something like 350 front, 450 rear. Having a higher spring-rate in the rear actually works better from a comfort standpoint, too since the car settles at the same time after going over a bump, etc. I never believed it until I installed Dinan springs on two of my other E28s. They used a higher rate in the rear and the car was far more composed daily and in high-performance situations like an autocross. I parted the other car before I ever got the chance to play with the springs.

The dampers are just as important as the springs. Honestly, for street use only, I don't see much point in coilovers. I'd put the money used for that into refreshing all of the bushings, etc. I think it will be far more rewarding, especially considering the structural weaknesses these cars have.