skydoc_17 Posted January 4, 2012 Share #1 Posted January 4, 2012 (edited) It’s that time of the year when many of us First Gen. VR owners are working on our bikes, so I thought I would take a moment and point out an issue I have discovered. After rebuilding over 100 First Gen. MKII VR (1986 to 1993) Rear Brake Calipers, I have noticed a trend that I wanted to share with you. Given that the MKII VR Rear Brake Calipers are at least 19 years old, and could be as old as 26 years, in the case of the 1986 model, Plus the rear of the MKII VR has one of the largest diameter rear rotors ever placed on a production motorcycle. The surface footage that is generated at the point of contact of the brake pads is so great, that the steel backing plates of the brake pads actually wear a groove in the Caliper Body! I have attached some pics of the groove worn in the body of the MKII VR caliper below. Now, this only happens on ONE side of the caliper body, so great care must be taken when inspecting the caliper when you change Rear Brake Pads. You will find this groove on the side of the rear caliper closest to the front of the motorcycle, and this is why many MKII VR owners miss this wear groove. If you find that your rear caliper has this wear groove, then replacement of the caliper is necessary. The reason being is the brake pads get trapped in this groove, and will not back off of the rotor after the rear brake has been released, causing the rotor to overheat and warp, or lock up. If the groove is not very deep, you still get reduced brake pad wear because the brake pads are staying in constant contact with the rotor. The first pic shows a cleaned up set of MKII VR Rear Caliper halves. The arrows are pointing to the groove cut in the Caliper Body by the Brake Pad Backing Plate. The next two pics are uncleaned caliper halves. This is most likely what the groove is going to look like when you remove the brake pads to replace them. I hope this information helps you with any pesky little rear brake problems you may be having. Earl Edited January 4, 2012 by skydoc_17 CRAYON BROKE! Link to comment Share on other sites More sharing options...
bongobobny Posted January 4, 2012 Share #2 Posted January 4, 2012 Yup! I have seen what you are talking about Earl, and it is not limited to Yamaha or motorcycles. Usually on automobiles it appears on the caliper mounting arm but sometimes you can see it on the caliper as well. I usually just file them flat, but that leads to a loose fit. I generally grease the mating surfaces with a good waterproof wheel bearing grease... Link to comment Share on other sites More sharing options...
jasonm. Posted January 4, 2012 Share #3 Posted January 4, 2012 FYI-replacement of the guide pins can cure this sometimes before it gets too bad. Yes, they are "guide pins" . But yhey also keep the pads from "floating" around. A part MOST do not change w/pads. Also a dab of high temp grease on end of pads backing plate like cars use can help some. But is not a cure. Since many say it just attracts dirt and the aluminum will still get "sanded down". Lucky for me I have spare calipers too. So this could also happen at the front?...they are the same basic calipers... Link to comment Share on other sites More sharing options...
bongobobny Posted January 4, 2012 Share #4 Posted January 4, 2012 Yes it can as I have seen it to some degree on fronts I have rebuilt, some very minor, others pretty bad... Link to comment Share on other sites More sharing options...
jasonm. Posted January 5, 2012 Share #5 Posted January 5, 2012 FYI- maybe if the fronts are bad...then it's time to move up to R1/R6 calipers... Link to comment Share on other sites More sharing options...
kf_sk_mccall Posted January 5, 2012 Share #6 Posted January 5, 2012 Poorman's fix: Clean up the grooves and fill with JBWeld. Let cure and then sand smooth. (if pads are wearing tapered, you have grooves) Link to comment Share on other sites More sharing options...
Gearhead Posted January 6, 2012 Share #7 Posted January 6, 2012 I just posted in some detail a few months back about my adventure with this problem. In my case, the groove was keeping one end of the pads from clamping on the rotor, so my pads were worn in a wedge. Most of the wear in the pin system was not on the pins themselves, but rather the holes in the calipers where the pins go through looked like eggs. The problem was most evident in the rear but starting in the front as well. I didn't want to pop for R6 calipers or whatever 'cuz I'm too cheap. I ordered some small bronze bushings from McMaster Carr, as well as some new pins. I drilled out the egg-shaped holes to the OD of the bushings and tapped them into place, restoring the fit of the pins in the calipers. I then filed out the grooves in the calipers. They are working quite well since. I took pics of the job but have not yet posted them. Jeremy Link to comment Share on other sites More sharing options...
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