2019 R6. My brake pads are wearing faster on the bottom half of the pads (on the leading edge portion). So the bottom pistons are extended out slightly more than the top pistons. It seems about even left and right and each caliper. It did it to my first set of Galfer HH pads, and now it’s doing it to a set of Vesrah, which BTW are about 100x better at stopping than the Galfers. Is this normal or an excuse to buy some new shiny Brembo calipers?
Solid disc rotors. Calipers might be nice, discs are less expensive. Could be that the upper piston bores are all gunked up with pad debris, effectively requiring more effort to move them while the lower pistons take up the slack.
Pretty normal, as the bottom half of the pad is the first to see friction, but if it's visibly skewed, there's probably an issue with alignment Measurements, top and bottom? More than 1 mm different?
What could be the issue with alignment? Both sides were like this, so it seems too consistent to just be drag on the piston. No wonder I was getting fade.... https://drive.google.com/file/d/1Zp0_Hz16Y9md1Iv56wqrQ62AV7Drj4-E/view?usp=drive_link
That seems pretty severe. Are you tightening the axle and pinch bolts in the correct order? Is your front-end straight?
I tighten the axle then torque the pinch bolts in the 1,2,1 order from service manual. The bike has been crashed, but it seems to ride fine and forks have been tested for straightness. Nothing suggests anything in the front is bent. Forks go in and out of triples fine. Axle goes in fine. I would think an alignment issue would cause the two side to wear uneven, but with both sides exhibiting the same uneven wear, I’m confused.
I'm looking for a theory of how something bent causes this type of brake wear so that I have somewhere to start looking. Ideas on what to check?
Start with this: Take the pistons out of the calipers and clean everything. Get every bit of grime you can off of the pistons. Either clean the seals very well or just go ahead and replace the fluid and dust seals with new ones. I use diluted simple green and nylon bristle brushes, then rinse with water, then dry the bare calipers with compressed air and then a heat gun to evaporate any water hidden in the caliper before reassembling. If you still have the same issue you have a weird problem somewhere.
And the pinch bolts are completely loose after tightening the axle, allowing the forks to self-align? And you do this alignment with the calipers off? If the forks are straight and slide in easy, that suggests the triple is straight as well. It's not guaranteed, but ya. I agree that I would expect the wear to be uneven if something were misaligned or bent. I'm just trying to check the easy things first before diving deeper. I have no other guesses for alignment issues. So I'd start looking into caliper issues.
Yes to all of that. Not sure if this is normal. A few weeks ago, I took off the top triple to remove clip ons without the front being lifted by the lower triple stand like I normally do. When I went to put the top triple back on, it wouldn’t align with the center stem bolt. So I lifted the front on the lower triple stand to unload the forks, and then the top triple went on no problem. I assumed the front flexes slightly when loaded with only the lowers holding it. But maybe there is something more to this?
Shit that is extreme! I would clean the shit out of the calipers, I even get a sand paper and hit the pins that hold the spring plate in so there is no binding. I would bleed the brakes too. Maybe you have some air trapped in there. Bleed enough to replace all fluid. Its a really simple system when you think about it. Clean and fresh should fix it. I would also fix it before you invest in calipers or discs as you may not find the root cause.
I rebuilt the calipers with new seals and stainless pistons. Most of the OEM aluminum pistons were corroded or worn about halfway or so down behind the dust seal that I couldn't see until I moved the pistons out further. I was surprised at how bad the pistons were. This is a 2019 with 5500 track miles. I'm not sure if the calipers were the problem, but they weren't helping anything. I'll report back after I wear down these new pads.
The pads are wearing evenly now. I also put Brembo rotors on at the same time I rebuilt the calipers, but I'm going to guess it was a piston / caliper issue since they were clearly worn /dirty. Problem solved. Thanks for the advice all! Wear issues aside, holy crap the brakes are so much better now. Not stronger, but very consistent and no fade. There is almost zero brake drag when I come off track. I don't know if it is the rotors, the stainless pistons, or everything being new and clean, but the combination is night and day. I think the pistons and seals got dirty and worn slowly over the last two years so I never noticed how bad they got. I might get a second set of calipers so that I can easily swap out to a freshly rebuilt set mid-season and deal with the cleaning in the winter.
If you just take some soapy water or simple green diluted with water and clean them with a nylon bristle every weekend or two, you shouldn’t need another set of calipers. Surprisingly don’t use brake cleaner, it is hard on the seals.
^^^ this right here. Spend your money on spares for other parts that are prone to crash damage instead.
