VFAQ: Shortening KYB Bumpstops for lower than stock springs
When you install shorter than factory springs it is necessary to trim the bump stops to keep the same shock movement depth or you will likely hit your bump stops far too often. If your car is anything like mine, your factory bump stops are completely dry rotted and crumbling.
Ok, this isn't neuroscience, normally you just hack off the top 1 to 1 1/2" of rubber off of the top of the factory bump stops before you install it. However, if you buy your bump stops from KYB, you can't do that and have the tips shaped as necessary to function like it should. Instead you have to cut a portion out of the middle of the bump stop and glue the tip and the main body back together.
My installation was for Eibach Sportline Springs, which ask for 20mm to be trimmed off of the stock bump stop. Pro-kits or similar springs that have a larger drop will require a bit more cut.
Parts required: KYB Bumpstops - I got mine at
www.tirerack.com along with my shocks and springs.
Tools Required:
A sharp knife - serrated works really well.
Silicone or some other adhesive. (I used silicone since it was cheap and laying around, but a actual rubber adhesive would be best)
Getting started: The front bump stops require more work so I started on them first. The major pain with them is that they are actually two pieces in the bumper portion, one hard center with the body wrapped around it. We keep that center for durability and function and move it.
First you'll want to cut the top joint that has the hard center in it just barely above the first valley. Here the line is already lightly scored across the bumpstop and marked with the green arrow.
Go ahead and cut it down to the hard center all of the way around. That will pull out and expose the center insert. Set this aside, we will be reinstalling it as the top of the bump stop.
Now cut the 20mm section out of the body (or whatever length your springs and shock body require). Here is the section I removed.
Now we need to create a recess for the insert to fit into the body of the bump stop. Grab your knife and go to cutting. It doesn't need to be pretty, as a matter of fact a rougher surface makes for better adhesion.
Once you've cut enough, sit the top insert on it and should fit right in with no problem and sit flat.
Pull the top insert back off and now you just put your adhesive on the surface of the rubber. Ok, so I got a little overzealous with the silicon gun - you don't need that much.
Sit the top back down and smooth out the silicone. Wipe off your excess and sit it aside to dry. Repeat for both fronts.
Now for the rears. They don't have another insert so it's pretty much hack and slash. Cut off the top section. Cut out your needed segment and glue it back together just like the other.
All finished - they will need to sit until they cure before being installed.
