Suspension compliance issues...

[bwh13]

I have the Bilstein HD's with Eibach Pro Sport (1.25" drop or so) with the IE sway bars on the 88 325is. Poly rear subframe bushings. With the TRM 15x8 wheels shod with BFG GSport 225/50-15's set at 30 front 32 rear psi, every little raised crack in the road jars the car.

It's almost as if the springs/shocks are just not moving at the initial point of impact on the sharp edge bumps. At higher speeds it's not as much of a bother, but below 40 or so it's just annoying.

I only have about 1K miles on the setup, but I would expect them to be broken in by now.

Any insight if this is the way it's supposed to feel?

[E30_fiend]

more than likely the shocks are blown. Never use Bilstein HDs on lower cars. They will blow 9 times out of 10.

Your best bet is to get some Bilstein sports and use those. I have a friend that used to run the billy sports with the eibach kit and it was actualy a nice ride. He had a little too much power so it squatted too much for his taste.


Get new shocks

[Stephen]

^what he said

You're probably riding on bumpstops and most likely blown.

[bwh13]

I don't think the shocks are blown. That doesn't make any sense given the way I've barely driven the car. I haven't hit any large bumps etc that would cause a blown shock. Lowering the car only 1.25 wouldn't blow the shocks either...

It may be the HD's are just too stiff.

[ShortSkinnyKid]

I don't think the shocks are blown. That doesn't make any sense given the way I've barely driven the car. I haven't hit any large bumps etc that would cause a blown shock. Lowering the car only 1.25 wouldn't blow the shocks either...

It may be the HD's are just too stiff.

The HD's aren't meant for lowered cars, the sports are. I would imagine the ride quality would be negatively affected by using the wrong shocks. They aren't designed for the lessened flow of travel.

I had 3 of 4 shocks/struts blown, lowered the car (with bilstein sports and H&R sports) and the ride quality improved dramatically.

[Alpine003]

Bilstein HD and Sports are high pressure shocks unlike Koni's which are low pressure. This could be the reason why you are experiencing those characteristics.

I personally prefer KONI's due to better ride refinement on a DD car with streetable rate springs. The low pressure design makes it more compiant over smaller rougher surfaces. But Bilsteins do take more punishment over the long haul hence being more reliable but not as refined imo. My impressions are based on owning Bilstein Sports, HD, Koni Yellow OTS, Tokico, KYB, FK, Suspension Techniques.

There are some shock dyno's floating around somewhere that demonstrates the dampening characteristics of both.

[Stephen]

And also, eibachs arent really 1.25. Theyre actually pretty low.

[E30_fiend]

Eibach springs sit you about 2 inches lower than stock. and HD's arent valved for lower springs, they are valved for stock height cars. I.E. if you drop the car on HDs, they are basically bottoming out shocks the whole time while driving because the valving isnt meant to allow that kind of compression.





Taylor

[bwh13]

OK that makes sense about the Eibachs being lower than they state, thus putting the HD's outside their intended stroke range.

Raising the car up a bit wouldn't bother me too much if I can get better sharp edge compression characteristics from the shocks.

Just hate spending more $...

[z31maniac]

Already been said, but yes it sounds like you are riding on the bumpstops. My S52 car is low enough that bumping my spring rates from 350/500 to 550/750 actually significantly improved the ride quality because the car was no longer hitting the bumpstops.

[bwh13]

Yes that would help me quite a bit too since the S52 I have does weigh more than the M20.

[Alpine003]

Eibach springs sit you about 2 inches lower than stock. and HD's arent valved for lower springs, they are valved for stock height cars. I.E. if you drop the car on HDs, they are basically bottoming out shocks the whole time while driving because the valving isnt meant to allow that kind of compression.
Taylor

This thought had crossed my mind but the op said every "little" raised crack and I thought that to mean very minor bumps in which it shouldn't compress enough to hit the bumpstops.

Also Eibach does have Pro Kit and Sportlines but not sure on the e30 applications. But even the Pro Kit tends to lower more over time. They've always had issues with sag from my experience.

Definitely get stiffer springs if you've got an S52 in there, that would explain the above...