Still not happy with suspension...

[z31maniac]

(This was a "Jay" conversation, not a "Ground Control" conversation. )

Jay

I hope the guy has free long distance!

Bazinga!

[bwh13]

Here is what I have learned so far:

The Bilstein Sport and HD have the same damping specs. The Sport can be used with shorter springs due to the length of the internal bumpstop (at least that is what I understand to be the difference).

With shorter springs, the Sport will still hit the bumpstops regularly, due to the available stroke length of the strut.

Everyone who has the Sports and shorter springs is riding around hitting the bumpstops all the time. Some don't mind it as they are not adversely impacted by this. Others, such as myself, think it feels like riding in my dads old truck.

I have driven some high dollar (Lambo, Ferrari, Porsche, Ford GT, etc) cars that had firm suspensions, but controlled the bump portion of the suspension travel with excellent results; not too soft, not too firm. This is what I expect the suspension to feel like.

Suspensions are supposed to use the bumpstops; how often they do is part of the equation when a shock/spring combination is assembled and on a car. In my case the Bilsteins don't appear to meet my criteria for an acceptable ride quality since they will allow the bumpstops to act like part of the suspension stroke more often with the shorter springs.

From what I can gather from the specifications of the suspensions BMW offered for the 325is back in 1988, the Bilstein Sport struts would work just fine with the available springs back then, specifically the M-Technik springs.

These springs gave the car approx .75" drop from the standard BMW springs (again, as far as I can tell). This amount of drop would work well with the travel available in the Bilstein Sports, keeping the suspension from bottoming onto the bumpstops most of the time; only large impacts would result in bumpstop compression.

For the E30, a compression stroke of approx 3" appears to be the optimum length. This means a stroke of 1.5" and a bumpstop compression of 1.5" should work (the bumpstops do compress, they just look like a solid piece). With the Bilstein Sport and the H&R Sport (and any other spring that drops the car 1.3"), the available stroke is siginifcantly less than that, since the struts were designed to work with the .75" lower M-Technik springs. So if the strut is working with a shorter spring, the available travel is reduced by the amount the spring lowers the car, more or less. In the case of the Bilstein with H&R Sport springs that travel is reduced by approx 1/2", compared to the travel available with the M-Technik spring. That 1/2" is all part of the bumpstop compression.

Using a shorter overall length strut with a shorter spring would allow the strut to maintain it's total travel close to the standard strut.

In addition to this, adding a heavier engine to the mix really requires a higher rate spring to compensate for the extra weight.

What all this adds up to seems to be that with the heavier engine and the shorter springs (which aren't really that much stiffer than the stock springs), the front suspension travel is just about gone, except for the bumpstop compression.

So I'll have to start over and figure out what springs and struts/shocks will best suite the way I want the car to ride, even if I have to give up some handling to do it...

Sorry for the long post

[brandondan1]

Good information. I recently went back to stock suspension because of this same issue (had bilstein sports). I'm sorry, but ride quality is a lot more important to me than being 'stanced', especially on a daily driver.

I'll have to look into Konis or ASTs the next time I lower my car.

[nando]

Here is what I have learned so far:

The Bilstein Sport and HD have the same damping specs. The Sport can be used with shorter springs due to the length of the internal bumpstop (at least that is what I understand to be the difference).

With shorter springs, the Sport will still hit the bumpstops regularly, due to the available stroke length of the strut.

Everyone who has the Sports and shorter springs is riding around hitting the bumpstops all the time. Some don't mind it as they are not adversely impacted by this. Others, such as myself, think it feels like riding in my dads old truck.

I have driven some high dollar (Lambo, Ferrari, Porsche, Ford GT, etc) cars that had firm suspensions, but controlled the bump portion of the suspension travel with excellent results; not too soft, not too firm. This is what I expect the suspension to feel like.

Suspensions are supposed to use the bumpstops; how often they do is part of the equation when a shock/spring combination is assembled and on a car. In my case the Bilsteins don't appear to meet my criteria for an acceptable ride quality since they will allow the bumpstops to act like part of the suspension stroke more often with the shorter springs.

From what I can gather from the specifications of the suspensions BMW offered for the 325is back in 1988, the Bilstein Sport struts would work just fine with the available springs back then, specifically the M-Technik springs.

These springs gave the car approx .75" drop from the standard BMW springs (again, as far as I can tell). This amount of drop would work well with the travel available in the Bilstein Sports, keeping the suspension from bottoming onto the bumpstops most of the time; only large impacts would result in bumpstop compression.

For the E30, a compression stroke of approx 3" appears to be the optimum length. This means a stroke of 1.5" and a bumpstop compression of 1.5" should work (the bumpstops do compress, they just look like a solid piece). With the Bilstein Sport and the H&R Sport (and any other spring that drops the car 1.3"), the available stroke is siginifcantly less than that, since the struts were designed to work with the .75" lower M-Technik springs. So if the strut is working with a shorter spring, the available travel is reduced by the amount the spring lowers the car, more or less. In the case of the Bilstein with H&R Sport springs that travel is reduced by approx 1/2", compared to the travel available with the M-Technik spring. That 1/2" is all part of the bumpstop compression.

Using a shorter overall length strut with a shorter spring would allow the strut to maintain it's total travel close to the standard strut.

In addition to this, adding a heavier engine to the mix really requires a higher rate spring to compensate for the extra weight.

What all this adds up to seems to be that with the heavier engine and the shorter springs (which aren't really that much stiffer than the stock springs), the front suspension travel is just about gone, except for the bumpstop compression.

So I'll have to start over and figure out what springs and struts/shocks will best suite the way I want the car to ride, even if I have to give up some handling to do it...

Sorry for the long post

pretty much nailed it

springs that are the "right" rate for you and your car, and good damping will definitely improve things. Stiffer doesn't have to mean poor ride quality, since that almost always comes from good damping not soft springs. I almost tripled my spring rate without changing much else, but since I stopped bottoming out all the time my ride quality actually improved significantly. Now I'm looking at another upgrade as my current struts are pretty well dead, I think I can keep similar rates and improve ride quality even more with better damping.

[Jean]

I have the same problem with H&R Sports + Bilstein Sports, and I much preffered my previous much stiffer springs with the same shocks. Can't wait to switch again.

When the road is smooth it's fine, but it's really shitty otherwise. The stiffer springs gave a stiffer ride, but it was more forgiving of really bad road surfaces such as sharp bumps and so on.

[bwh13]

Yes on smooth roads the set up works just fine, but any sharp edged bump just about makes my teeth rattle. Not my idea of a fun to drive car.

I thought about going to stiffer springs, but then realized I just should have ponied up and bought the GC kit with SA Konis to begin with.

Will be pulling off the Bilsteins and H&R's within the next month and getting the GC kit...