I just successfully replaced the front and back rotors on my 1989 K100. I
thought the the following might be helpful to the group.
My bike is equipped with ABS so that meant that there is an ABS gear tooth ring on the disk carrier. The hardware supplied was stainless 5 mm x 16 mm socket head screws and locking nuts. These are too long for the side with the ring, and the nuts were too thick also. The solution was to order SS M5 x 14 mm socket head screws and thin nuts from Barnhill Bolt in Albq. NM from their home page (barnhillbolt.com) and these fit like a charm. Add some Lock Tite red to the mix and I think it's going to work just fine.
To remove the original stainless steel rivets was a trick. It takes the right tool to do it right. Anything else would have taken a lot longer and damaged the carrier. I used my buddy's compressor and high speed grinding tools. For $1.65 each I bought 2 - 1 inch dremel style grinding stones and one side cutting disk also 1 inch in diameter. You need a couple of 2X4's to support the assembly and a 3 mm drift punch.
Grind the tops of the rivets off. You will need to be sure that you get every head completely. Then set the assembly on the 2X4's resting on the disk. Next take the punch and start pounding the rivets in a criss-cross, lug nut style pattern. The rivets will move only small bits at a time. Patience is required here. Once I got the rivets halfway out all around, I took another short 2 x 4 and pounded the carrier around until the two parts separated. There are 20 rivets per disk.
Next I needed to remove the rivet backs from the two carriers that have the ABS ring. Here I put the carrier in a vise, padded of course, and started the tricky part. I used a small pair of vise-grips to hold the rivet end and push the rivet as far back against the ring as possible. I again used the high speed air grinder and the little side cutting disk. I held the pliers and inserted the cutter between the rivet head and the carrier and proceeded to cut each of the rivet heads off and pull out the rivet with the pliers.
The whole job to remove a disk from a carrier, once the carrier and wheel have been removed, is about 1 hr for the first, and 45 min. for the second, and it took me 30 for the third. If you are considering undertaking this type of a job and don't have a compressor and grinding tools, RENT THEM. In the end it will save you time, injury, and damage to your machine. This job required the right tool.
Installation was a snap. It takes 15 min. to install the disk and use the lock Tite. I would also recommend that you replace the bolts that hold the carriers to the wheels as a safety precaution. Also the rear carrier is held on by two little screws, get them also. I got them from Hammersly, also from their web page.
With the new disks one and I also put on Braking Systems SM-11 carbon fiber brake pads, it started to snow. I'm looking a 6 new inches, so the test ride is going to have to wait. I will need to remember to slowly brake in the new pads and disk if I want them to last.
The only question I have is this, Did my rear pads wear out at twice the rate as my front due to the fact that the close fit of the disk and saddle bags keep them hotter and therefore a lot quicker?