Cut the Bistein bump stops or not?

[Steve W]

I guess I've read every post regarding this subject but haven't really found a definitive conclusion. I'm about finished reassembling my front end with new 22 mm Sanders bars, Elephant racing polybronze bushings, turbo tie rods, rebuilt Bilstein sport shocks. But before I insert the Bisteins back in their strut assembly tonight, I can't figure out for the life of me if I should shorten the bump stops or not. I'm running the standard Euro ride height of 25.5" in the front with 225/40-18s and rolled fender lips that barely clear by a couple of millimeters. I understand that bump stops are an intergral part of the suspension design, but I don't want to be riding them on a hard turn. Any opinions greatly appreciated. Thanks!

[304065]

If you hit the bump stop in a turn the effective spring rate goes to zero and you have an instant spin on your hands. Carroll Smith goes into great detail on how to modify the bump stop in "Tune to Win." If you anticipate using the car that aggressively I'd shorten them.

What is the spring rate of the 22 bars? How much weight transfer and aero force do you expect, is it likely that you will ever get full deflection?

[Vipergrün]

I would say a definate *yes*, especially if you plan to go lower at any point. You should also remove that thick washer on top of the strut housing. I have Bilstein Sports all around, 22/30mm t-bars and upgraded sways and cut off 2/3 of the stops. Before I upgraded to 22's up front, I did get some rubbing on hard cornering running 225's after cutting down the stops.

-B

[Schrup]

When I took my old ones out they had all but disintegrated. I think there were 3 or 4 lobes but could be wrong. When the factory sent back my revalved inserts with the new bump stops I requested they only had two lobes. I wouldn't go any shorter than that. I have done the samething as you Steven, except for the polybronze (I used polygraphite) & I upgraded to Carrera sways.

[tops911]

Smart Racing Products on their web sight (i think) shows how to do it. When I had my rear shocks revalved I cut the bump stops per their instructions. My car is lowered quite a bit, and looking at the wear on the shaft it needed it.

[Steve W]

When my Bilsteins eventually failed, I hit the bump stops all the time on some bad roads here in L.A. Perhaps that's what saved me from destroying the chassis and rims after finally figuring it out. The new Sanders Engineering 22 bars are about double the spring rate of the original Carrera t-bars. I am expecting not to bottom out as hard as before, along with the renewed Bilsteins which are now as hard to compress as I remember them.

It's funny, I just talked to Rich at Smart Racing Products a few minutes ago, as they wrote the original bump stop instructions, and couldn't figure out if I should do it or not. If I have it lowered to say 24.5 inches, they definitely recommend it. Perhaps I will only cut off one of the three lobes.

[84toy]

Steve, my rebuilt Bilsteins will arrive on Friday. I told the Techie that I was lowering my car and that I was especially worried about the rear bottoming out. He said that they were going to machine me some rubber stops that were "progressive" so if it bottomed out it would be softer. When I said I was a machinist and I could do it he said don't worry about it, we'll do it for you. Call me on Friday and we'll see what the surprise is. BTW, Bilstein was great to work with. Told em what I had, what I wanted and the guy just said "we got just the ticket for you" I'm anxiously waiting.....Shameless plug......my chip works great!

[Steve W]

Thanks Paul, I'd be interested what Bilstein machined up for your rears. Perhaps you could post a pic. My rears are going in next for a revalve for the 29 tbars that are going on. BTW, those two piggybacked alarm systems you had posted from your car looked quite mad! What ended up being the cause of your car not starting?