[subieworx]

One of things that has always bugged me about this car is how rough it is over sharp large bumps. It really is brutal and only made worse with lowering springs. After installing the H&R sports it became mostly horrible to the point I don't like driving the car on a regular basis and find myself dodging bumps at every chance.

There are two issues that cause this problem on the car. The first is there is almost no bump travel in the suspension. As measured, there is only 3.75" of total stroke in the front shock which is nothing. I'm used to building and tuning subaru suspensions were we typically have twice that on a good set of coilovers. (cheap shit can GTFO!)

This lack of travel is noticeable on the stock springs, but once the car is lowered, such as on H&R sport springs, it's really apparent. In measuring the bump stop up front it comes in at 2.5" total free length. Long story short once the car is under it's own weight, the bump stops are about half compressed. Seeing as we have many bump stops around (we are a suspension focused shop after all) I figured I would swap in some different ones to see how it rides. the following pics are of the new v old stops. I will post reviews once I get it aligned and on the road later on.

Stock bump stop on fully extended strut shaft.



Bump stop I will be trying. It is almost half the length of the stock one.



Side by side.

[3X3=5]

Thanks for posting some hard numbers on the suspension travel and bump stops. I asked about this a few weeks ago and the thread didn't get very far. But I basically saw the same thing as you - with so little travel to begin with, the suspension must be riding on the bumps stops once lowering springs such as H&Rs are installed. It made for a terrible ride. I asked what the hell am I supposed to do here since you're not supposed to trim bump stops, but the suspension shouldn't ride on them either. I guess the solution is aftermarket. Which bump stops did you use here?

My previous post on this topic: http://www.e90post.com/forums/showth...rim+bump+stops

[subieworx]

The issue with trimming bump stops is you lose progression of the stops. Stock, the bottoms are very soft getting progressively more stiff as they rise to the top. Most people like to cut the bottom run off leaving a stop that is very hard and engages harshly. The stops I am using are designed for situations where there is little bump travel. They are soft at the beginning, though more stiff than the stock soft, and ramp up to stiff very quickly. This should allow the shocks more travel to damp the motion of the spring before "going solid" once it gets hard into the stops. We'll see how it works. This is all just theory at the moment, but theory that we have applied many times in the past to other cars.

[Chowbow]

Ground control also has aftermarket bump stops for this application.

[francisomar]

For what application were intended originally those bump stops?

[ajsalida]

What are those original bump stops from? Sport package or what? I was just looking over RealOEM and there are several sizes of bump stops available from the factory (and I am assuming different stiffness characteristics).

BTW I have run shorter race bump stops (off of coilovers) on street Bilsteins with lowered springs (on another car) and man they were sweet until I used up all the travel...also ran Bilstein + H&R sports on an e36 M3 with trimmed stops, same comments. Bang!

The decreased travel from lowering + increased segment of travel w/o bump stop + harder short stop makes for some high shaft velocities when bottoming out.

I am setting up to swap out my xi spring for standard sport springs and was going to try some stiffer factory bumps, they're pretty cheap. Sticking with factory shocks for now.

Lot of trade offs.

[subieworx]

You should see what the stock bump stops look like then. They are more than half way compressed and every moderately sharp bump hit forces the entire front end of the car to rise as there is no travel left. As a comparison, with these stops in there now there is no free play (travel before stops) in the system. Even with these shorter stops...

Now the problem....I'm beginning to think there is no room for actually lowering the car outside of using shortened shock bodies to get more travel. Switching to the shorter bump stops seems to have lowered the front end of the car 1/8" or so. This is just further proof to me that these springs are horribly designed.

Those are the stock bump stops from the sport package.

After aligning it I took it out and it definitely feels better over 80% of bumps. It is more controlled and less jarring. It is still harsh over large bumps, but that won't be solved without going back to OEM springs.

[ajsalida]

Originally Posted by subieworx

Now the problem....I'm beginning to think there is no room for actually lowering the car outside of using shortened shock bodies to get more travel.

This is basically the conclusion I've come to on every car I've ever lowered. You have to have some suspension travel off the stops or it's pointless.

Having said that of course I'm going to TRY the OEM "i" sport springs on my 335xi with shorter sport bumps stops. I got them cheap so we'll see what happens. At some point I'll go with Bilsteins and some other type of spring. I was not pleased with the H&R sports on the Bilsteins I had on my old M3.

A lot of manufacturers say they engineer their components specifically for blah blah blah but that often turns out to be a load of crap.

Appreciate the info on the stock bumps. I think there is an M3 version that is shorter, I may go with that.

[subieworx]

Originally Posted by ajsalida

A lot of manufacturers say they engineer their components specifically for blah blah blah but that often turns out to be a load of crap.

Ain't that the truth. Can't tell you how many times I have run into this over the years in this business.

[3X3=5]

Originally Posted by subieworx

You should see what the stock bump stops look like then. They are more than half way compressed and every moderately sharp bump hit forces the entire front end of the car to rise as there is no travel left. As a comparison, with these stops in there now there is no free play (travel before stops) in the system. Even with these shorter stops...

Now the problem....I'm beginning to think there is no room for actually lowering the car outside of using shortened shock bodies to get more travel. Switching to the shorter bump stops seems to have lowered the front end of the car 1/8" or so. This is just further proof to me that these springs are horribly designed.

Those are the stock bump stops from the sport package.

After aligning it I took it out and it definitely feels better over 80% of bumps. It is more controlled and less jarring. It is still harsh over large bumps, but that won't be solved without going back to OEM springs.

I'm glad someone else finally agrees with me!! When I posted on this before everyone said "well it shouldn't be riding on the bump stops with the H&R sport drop" but it was pretty damn sure it was clear that it was. Then when I asked about cutting them most people said "no you can't cut them, it's bad, etc." Well WTF then. So really the only solution with the H&R sports (at least on stock shocks) is to get new, shorter bump stops. Or my solution was to just get coilovers, though I haven't had a chance to install them yet.

[subieworx]

I think the best solution for performance and ride quality on stock like shocks is to go back to the stock springs. Bump stops help but are not perfect. I will say that the car feels much better than before. I have driven about 45miles since the swap and definitely can stand the ride more. I think swapping in shorter bump stops is a MUST for anyone running lowering springs.

[francisomar]

So, you are using zsp bump stops or are they for another car application? I'm asking cause I am doing some suspension work next week and want shorter ones as well, I am now on the factory zsp suspension

[subieworx]

They are different.

[V1_R]

Originally Posted by subieworx

They are different.

... so where are they from then matey?

[subieworx]

Can't say. But you wouldn't be able to buy them anyway.

I'm not completely satisfied wit them either. Seems that h&r either purposely or inadvertently is using the stock bump stops as part of the main spring rate as the car is .25" lower now and causes some rubbing in the front. I am thinking about going back to the stock springs for noe until I get some coilovers.

[francisomar]

Maybe getting a similar in height poly bump stop would be better than getting a shorter one

[Imperator]

How much more/less apparent is that with the Eibach Pro-Kit over the H&R? I assume the Eibach springs are using a rate that is closer to OEM/Sport, although they don't lower the car as much as the H&R springs do.

Has anyone pulled out part numbers or diagrams from the new BMW Performance suspension kit? I assume it is packaged with different springs, shocks and bump stops.

[marconi118]

Dinan uses on the E92 M3 the bump stop of the Z3 E36 (read on one tread in the M3 forum) but I could not find out if it is a Z3M or a Z3 3.0i and the part No

[marconi118]

Originally Posted by Imperator

How much more/less apparent is that with the Eibach Pro-Kit over the H&R? I assume the Eibach springs are using a rate that is closer to OEM/Sport, although they don't lower the car as much as the H&R springs do.

Has anyone pulled out part numbers or diagrams from the new BMW Performance suspension kit? I assume it is packaged with different springs, shocks and bump stops.

Yes the performance system has shorter (0.5") stops

[subieworx]

Here's a pic of the Z3M bump stop. I will order one of these up tomorrow to take a look at. It appears to be about .5" shorter than the stock 335i sport bump stop.

[hatred]

should be lower.

[subieworx]

Here's the difference between stock and the Z3M bump stops.

The z3m stops are much softer to start and ramp up to very stiff very quickly. The first .5" is softer than the stock first .5", but go to the same stiffness after that.