Bilstein bump stops

[chrismorse]

Most of us end up rebuilding our suspensions and replacing shocks. Bushing and T bar replacement requires setting the front and rear heights, then aligning.

It would be very helpful to know approximately how much we can expect the heights to SETTLE, so we can estimate a starting point to set the height.
Additionally, it would be nice to know how long it takes for this settling to occur, so we can get on with corerweighting and final alignment.

With this in mind, does it make sense to just use fender heights to do the initial height adjustments and rough align, so we can put the required miles on the shocks???

And finally, Is there a consensus on a "wise", (sorry Wayne), number of miles to put on the car before weighing and aligning the car. I would expect it to be shorter for cars that are routinely flogged and longer for the cars and coffee, easy driving.

Thanks,
chris

[Gretz]

Originally Posted by chrismorse

Most of us end up rebuilding our suspensions and replacing shocks. Bushing and T bar replacement requires setting the front and rear heights, then aligning.

That's the boat I'm in right now. Doesn't seem to be a consensus on many of these issues. Bilstein still hasn't gotten back to me. I totally get that Konis might be better for a lowered car, but mine isn't slammed, it's just lower than Euro.

I replaced my torsion bars with 21/28 bars and replaced the front inserts with B8s, and the rears with the yellow Street/sport model Bilsteins. Both of these are slightly shorter in total length from the standard B6 versions. This was based on advice from Bill, among others. The stiffer spring rate would dictate less suspension travel overall than the old worn original stock bars and shocks. I think the chances of hitting the limits of shock travel are low, but I'd still like to figure out the right answer on the bumpstop / spacer question before I throw the rears on the car. Then I can worry about how much settling to give the car before corner balancing. Unfortunately I can't go far without at least a basic alignment since I literally just replaced everything.

[Solamar]

I did quite a bit of research into bump stops when I setup my suspension.

First, there are the old and new style rear Bilstein bump stops -



I spoke with Bilstein about modifying the new style bump stops and/or deleting the hard plastic spacer. They made it clear that the spacer is required to prevent internal damage to the shock. Also, the soft bump material is designed to slowly ramp up spring rate in hard turns. Would be bad to have a big jump in spring rate mid turn. Trimming NOT advised.

I made this drawing to help me understand shock travel and bump stops -



My car is about 25.5" height to the fender lip (on 16" rims). At that height I have about 1.75" of rear suspension travel before I'm into the bump stops. If my car were 1.75" lower, I would be riding ON my bump stops and shorter shocks would be required. I'm currently setting up a set of 15" wheels for autocross that will lower my car ~ .75" but this will not affect my suspension travel. So keep wheel diameter in mind when comparing ride height.

Another interesting bit I learned is that most sports cars are factory designed to corner ON the bump stops. With that in mind, do you really want to trim the bump stop, creating a larger jump in mid corner spring rate?

['78 SC]

Solamar,

Nice diagram, but the Full Compress drawing appears to show the bump stop passing through the top of the shock body. Or does the entire bump stop compress down from 2.11" (first drawing) to 0.44" ?

[Solamar]

Originally Posted by '78 SC

Solamar,

Nice diagram, but the Full Compress drawing appears to show the bump stop passing through the top of the shock body. Or does the entire bump stop compress down from 2.11" (first drawing) to 0.44" ?

I just cheated on the drawing and did not draw a compressed bump stop I'm really not positive how far the bump will compress, but the .44" dimension is when the shock shaft bottoms internally = Bad.

[Gretz]

Based on previous information related to Smart Racing Products, I reached out to them last week. They are awesome folks with excellent customer service. I spoke to Craig for quite a while and he provided a wealth of good advice related to my particular suspension setup. It’s probably best not to just pass along his advice wholesale, lest someone assume his suggestions are correct for them. I’ll just say that I will certainly be supporting them in the future and will recommend them to others. Good people and their companies are what makes aircooled Porsche folks the best around. Thanks again, Craig!