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      07-18-2012, 10:06 AM   #11
Brian_VACsales's Avatar

Drives: E92 M3 VF Supercharged, 135i
Join Date: Feb 2011
Location: Philadelphia, PA

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A few people have asked about bump stops. This is why JRZ does not use them:

This is a copy/paste from the MAN in Holland.

1. We are not in need of a bumpstop due to our design philosophy. We are always using high compression forces in relation to the rebound forces. We know that that is the way to go (because of years of development and testing, as you know, we win races). So reaching the end of the stroke with a high velocity will almost never happen due to the high compression forces.

2. The high gaspressure also helps with this. We set our dampers with a high gas pressure. When compressing, this force rises. The more you compress the damper, the higher the gas pressure will be as well as the resistance in compression.

3. When you install bump stops you actually insert a extra spring on the end of the stroke. So what happens when you hit the bumpstop is that the spring rate goes up exponentially. The bumpstop will consume this compression force and will give you (almost) the same in rebound force. So the bumpstop throws you back up. When you are cornering and for some reason you are hitting the bump stop, you will first compress the dampers and bump stop. And while you are still cornering, the bump stop throws you back up!!

Having said all this, we’re not in need of a bump stop. We always design our dampers to work superbly without any need of a bumpstop. That is the way to go. You can find a solution for a problem, but it’s better to resolve the problem so it doesn’t occur anymore.
Brian Casella
Sales Representative, VAC Motorsports
Office: 215.462.4666 | Fax: 215.462.4667 EXT 13 | Email: