2008 CR 125 So at my last enduro, which was a sloppy mudfest, I started to have some front brake issues. My lever, which has been feeling a bit spongy the last few races, progressively pumped up to a super-hard lever pull, which culminated in a dragging/locked front wheel. The pads were very worn, maybe 1mm from the backing plate. I had been stuck badly in a couple mud ruts, so I figured that I just packed enough mud into the caliper that the sliding pins weren't sliding any more and that was why it wasn't releasing. I cleaned up the caliper in a puddle at a reset and went into the final section, where the front brake locked up in the exact same fashion. So I pried the pads apart and finished the race with just the rear brake. I immediately cleaned everything up and put in new pads. I checked the fluid level, which was okay, but the lever feel was still spongy. Today I flushed and bled the system, but it's not behaving right. First, when I was trying to build up pressure in the line to bleed at the caliper, I would have to pump the lever 20-30 times to get ANY pressure, and what pressure I got was very slight. There didn't appear to be any air coming out at the bleeder after several rounds of this. In fact, I probably flushed four resevoirs full of DOT 4 through the system in this fashion, and the lever just wasn't coming up to good feel. I finally got a little bit of pressure at the lever, put the resevoir cap on, bled one or two more times and tried it out. Lots of mush at the lever, but some braking action. If I pull the lever just about to the bar, I can get some lockup on pavement. What's going on here? Any ideas? I bled the back brakes with no problem--easy pressure buildup at the pedal during the bleeding process, so I don't think my bleeding technique is suspect. I just want that two-finger stoppie front brake I used to have!
Air can get stuck where you can't get it out. Bleed the system at the banjo on the master cylinder, as well as the one to the caliper. If that doesn't work, back bleed the system by taking the caliper off its mount and pumping the brake lever till the piston extends a ways, but not till it comes out, making sure that you don't let the reservoir go dry while you are doing this. then get a C clamp and squeeze that piston all the way in. All the fluid will come out of the reservoir at the top, so have something in place to catch all that. Remount the caliper and pump up the brakes. That procedure will often do the trick.
Good info on bleeding at the banjo bolts and the backbleed method. I'll give that a try. Any ideas why my brakes would have started to drag and lock up like they did?
I'd have to guess that it was the mud and moisture. during a ride in a heavy downpour in the high desert a couple of months ago, my front brake got mushy and stayed that way till I bled it. If contaminants get into the brake fluid, it can cause weird things to happen, like the fluid will overheat and expand causing the brakes to drag or lock. All that mud like you were riding in reduces the clearance between your pad and rotor and can cause things to heat up from the friction, even when you are not on the brakes..
I had something very similar to this happen on a ATV, but I also had some leakage at the caliper piston. On this, the piston and seal wore out(and pads) causing the piston to want to over extend and jam sometimes locking up the brakes, and a bit of a mushy lever at other times because of a leaking caliper piston seal. Most likely your problem is due to the condition you were riding in and the condition of your fluid and/or air. But maybe check for a little leakage at the caliper piston anyway.
Take the master cyl. off the bars and find a way to hold it so it's the highest spot in the system when you bleed it. I use a GPS ram mount to hold mine, but there are other ways. It's surprising how many tiny bubbles can get in a closed system. If you don't get the MC to the highest spot, it's very hard to get any bubbles out of the high point in the brake line.
Here is one of the biggest reason of disc brake drag.. Drum roll please... When removing the front or rear wheel the pads are slightly away from the disc.. Now if you put new pads on or a new rotor on the amount of oil in the master cylinder is lower then the new pad thickness.. By pushing the pads back to slip over the disc you pressurize the master cylinder and that positive pressure will cause brake drag. Also as the pads wear down or simply adding more fluid to make up for worn pads and then you replace the pads and push them back in that really pressurizes the system. The fix.. Any time you do a front or rear wheel removel and then put back on.. pump the brakes to set them release the pedal or lever and remove the cap from the master cylinder and you could hear the air or the fluid will splouge out .. recap it and life is good Brake drag on the front wheel could be from not centering the front wheel.. but thats another story.. Hope it helps Chow, Carl
Try searching your brake line to see if it has a weak spot in it. If it does it can blow up like a balloon and it is hard to find. I had a katoom that did it and I bought new MC and rebuilt the caliper and was bleeding it forever. Took to dealer and the breakline when squeezed had a weak spot.Made me mad cause they found it right away. Just thought!
Well, I think I figured out the problem. After a couple of races with a sub par front brake, I noticed a distinct CREAK from the caliper when pulling the lever. This was at a stand still in my garage. I pulled everything apart to find that the anti-vibration clip, or whatever it is that rests on top of the pads and against the caliper, wedged between the edge of one piston and the opposite side of the caliper. It was preventing the one piston from pushing on the pad, as well as preventing that side of the caliper from sliding together. As a result, I had only one piston pushing on the pad, and to get any squeeze on the disc, it had to flex the caliper since one side wouldn't slide. Thus the CREAK. I just removed the anti vibration thing and put in new pads. Welcome back, firm lever and brake feel!
