Fork Spring Replacement

The forks were very soft, hard braking caused them to bump out. I decided to replace the springs and ordered the “Compression Spring Reinforced” from BMW (part number 06  31 42 1 232 017).

I took off the handlebars and placed them on the tank covered with a thick rag. I removed the two fork caps with a simple homemade tool – two 4 mm bolts through a piece of aluminum.

Underneath the caps are two 36 mm “spring guide supports” (see red arrows) that need to be removed to get the springs out. The center nut on the steering stem also needs to be removed, it is a 36 mm as well. 

Those spring guide supports are very flat, if using a socket it should be modified.

 

 

I ground down the socket on a bench grinder (removed the chamfered part). The allows the socket to go deeper over the spring guide support and get a better grip. If you have access to a lathe, even better. Ideally you want to find a socket with 6 points, my hardware store only carried a 12 point, but it worked out.

I tried using a breaker bar, however they wouldn’t move. Even with the impact tool it needed quite a beating to come lose. Everything ultimately went fine though.

 

The springs came out relatively easily. Pull them out slowly, so the fork oil can drip off and doesn’t splash all over the bike. 

 

The new “reinforced” springs were about two inches shorter than the ones I pulled out, although I could tell that they were stiffer.

 

The BMW springs have a white dot at one end. This end needs to go to the top.

 

I decided to add spacers to increase the pre-load. I used a 3/4 inch PVC pipe and cut off two 1-inch pieces. 

I already know that I have to go in here again, since I have to change fork seals and steering bearings, so this gives me a starting point to test and I can always modify this later.

 

This is how the spacers go over the spring guide support.

Note: After riding like this for a couple hundred miles I removed the spacers while I replaced the fork seals. Forks were too stiff and for me the progressive springs are just right without spacers.

 

Putting everything back together is simple. Insert the springs, add the spacer (optional) and push down the spring guide support to compress the spring while at the same time threading it in. This requires a bit of force, especially if you add spacers. I put on some leather gloves, placed myself right over the fork leg, pushed down hard and turned at the same time. It took me a few tries but they went in fine. Don’t forget to torque to spec.

While I had everything apart, I put my polishing wheel to work and shined up the handle bar clamps, the triple tree and the caps.

I took the bike out for a test drive, it is much better, but as mentioned above, I ended up removing the spacers later.