Quote:
Originally Posted by Jonny954
Sorry for the dumb question, but what exactly is the 'Bump stop'...??
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It's not dumb if you don't know the answer
The bump stop isn't really it's correct name any more, it's technically called a micro cellular shock absorber, or something equally catchy. The idea is that the springs do most of the work taking the weight of the car as it bounces along our perfectly made, flat roads
and the piston moves in and out of the damper as the springs compress.
The bump stop fits over the piston of the damper, effectively preventing the damper from 'bottoming out' under extreme compression. As it does so, because it's made of foam and has been designed by very clever people who know all about such things, the shape, size and composition determine exactly how it compresses.
This means that as the damper reaches its limit, instead of going "smoothly, smoothly, CLUNK" as it bottoms out, the bump stop adds an extra little bit of "smooth" to the last little bit of compression - and they're an integral part of the whole suspension setup.
People who have changed from stock to sport or aftermarket suspension have reported that the stock bump stops are too long, and when shorter springs are fitted the damper piston no longer has enough travel to do its job correctly - or in extreme cases actually has no travel at all, and the car is effectively riding on the bump stops. Changing from stock to a shorter bump stop gives back to the damper the extra travel that's been taken away by the shorter spring and lets everything work properly again.
Having had mine apart yesterday, there was no need to fit shorter ones to the MSport setup, the OE parts would have been absolutely fine. But given the state they were in, and for the relatively low cost, I'm very glad I had new ones to put on. I can't imagine those horrible old things actually did anything any more!!
HTH