Is wheel rate supposed to be equal front to rear?

[THEhomelessONE]

Running 500f 800r, and I've noticed on dips the rear drops more than the front and it's annoying. What characteristics are there with equal wheel rates? I'd be pretty close to equal with 500f 950r.

[Mr. Tasty]

First of all, those numbers refer to lbsf/inch. 800lbf/inch means that 800 lbs of force is required to compress the spring by one inch.

The reasoning for increased rear spring rates, is because of the design of the e30 rear suspension, and also to increase over steering tendencies (which is considered more sporty.)

So for an answer, no the rear should not be dropping more than the front over bumps, the exact opposite.

[LJ851]

There is more than spring rates affecting this situation.

[camshaftgsxr]

Effective spring rate compared to actual front to rear weight distribution is what you need to be looking at 0.45 [x spring # lbs.] for the rear suspension, and 0.88 [x spring # lbs.] for the front suspension. Weight dist is about 53% ft 47% rr

shock absorbers will affect this as well. If you are using the koni single adjustable shocks then fiddle with the front rebound settings some to see if you notice a change.

my car is on 585# front springs and 750# rear springs and I don't notice any sort of discrepancies front to rear.

your springs 500# ft 800# rr = 440# ft and 360# rr given the 53/47 distribution of the e30 you are within a couple of pounds of being even given your spring rates and vehicle weight balance front to rear.

my springs 585# ft 750#rr = 514.8# ft and 337.5# rr blah blah weight dizzy blah blah blah blah softer in the rear, I prefer it blah blah infer what you will.



could be in your head as well...

[THEhomelessONE]

I know the verts are heavier in the rear than other e30's, and I have a Luke box back there with a couple amps. Threw my old eibach prokits on my cousins eta, and her car is a good 2 inches higher in the rear than mine was, front stayed about the same.

AGX's on full stiff all around, the rear definitely feels softer going over dips high speed, reason I started looking into wheel rates. Front wheel rate is 440, rear 360. Has anyone here tried equal f/r wheel rates? Worried how it will handle.

[camshaftgsxr]

it would be even worse than it is now, if it feels too soft now in the front and you are using a 2.5" coilover spring you can get a stiffer spring for about 150$ from eibach or swift, generally any deviation from effective wheel rate matching corner weights is to induce or reduce understeer or oversteer

[THEhomelessONE]

The front feels fine, it's the rear that feels soft. I think miata guys run matching wheel rates, wondering why BMW guys don't.

[nrubenstein]

Mostly, BMW people do not run matching wheel rates in coilovers because the decrease in ride quality is not worth the benefit.

You frequently see roughly matching wheel rates in non-coilover spring setups, but once you get to sufficiently elevated rates, it doesn't scale well. (Also because spring kits tend to be at least somewhat progressive, which offsets the ride quality issue.)

Also, people are frequently solving for rear grip, which generally means that you don't want it to be too stiff. Don't forget, also, that the rear suspension has a lot more travel available than the front. Simply solving for "dipping" is not a good way to set up the car.

[THEhomelessONE]

Makes sense. I don't care about ride quality, as long as the car isn't falling apart. There is an annoying part of the highway I need to slow down to 65 to not rub in the rear. Fenders are rolled flat, but the tire sidewall rubs against the fender arch. 225/50 16x9 +25.

So should I avoid using a 950r, and look into stiffer dampening instead? Was going to get rid of the rear sway if I went 950 too.

[lukeADE335i]

The simple answer is your rear tyres are too tall - 225/45 R16 is the correct size.

As for the rear, don't forget e30s tend to squat in the rear so you can get power down out of corners.


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[THEhomelessONE]

I guess I'll start saving towards better shocks, hoping to hear from someone having tried equal wheel rates in an e30.