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Brake Dragging Sound. Need Some ideas


trikpat

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Hey guys. Hoping to get some ideas.

There's a weird grinding noise from the front end of my bike (2010 DCT). The sound is very noticeable at low speed (10-30 mph) like the brakes are dragging. But it goes away at high speeds. Even just moving the bike around the garage sometimes you can hear it.

It started a while back when I got caught with some heavy rain while riding and that's when the grinding sound started. I thought maybe some dirt got stuck on the calipers so when I stopped to check the brakes, the front wheel wouldn't turn. As in it was locked in place, I had to move the bike back and forth for a while until it released.

Went home and thoroughly cleaned the calipers with some brake cleaner but sound is still there.

I installed a new set of  EBC sintered pads thinking it was the pads  but it's still there. A mechanic told me maybe it's because the pads are brand new and that I should give it some time to set.
Well I've done about 500km now and it's still there. I've tried spinning the front wheel by hand. It moves freely and it will spin about 1 and 1/4 turns before it stops but the sound is still there.

Also, I've encountered this about 2-3 times now. Early in the morning when I try to start the bike, the ABS light would flash. I pump the brakes a few times and it goes away.


I also noticed a section of the front left bearing seal was elevated. Could it be the bearings need a replacement? Does broken bearings sound like it it's brake dragging? 
 

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Bearings can have a grinding sound but they would have to be really far gone or dried out. I would pull the front wheel and inspect them. Usually if a brake pad rubs it is because the piston is not releasing well enough to allow the pad to “relax” in position or you have a bent/warped rotor. While you have the front wheel off see if you can have the wheel/rotor inspected for run out.

 

As for me, I usually pull the caliper off the bike and activate the brake while I’m looking at the pistons, if I see that the pistons are not moving evenly, then I know there’s an issue. Conversely, when pushing the pistons back in, by pressing the pad in towards the pistons, they should move evenly. Again, if this isn’t the case, then I know there’s an issue. Normally while the pistons are out as far as they can go, I give them a more thorough cleaning.

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10 hours ago, Duc2V4 said:

Bearings can have a grinding sound but they would have to be really far gone or dried out. I would pull the front wheel and inspect them. Usually if a brake pad rubs it is because the piston is not releasing well enough to allow the pad to “relax” in position or you have a bent/warped rotor. While you have the front wheel off see if you can have the wheel/rotor inspected for run out.

 

As for me, I usually pull the caliper off the bike and activate the brake while I’m looking at the pistons, if I see that the pistons are not moving evenly, then I know there’s an issue. Conversely, when pushing the pistons back in, by pressing the pad in towards the pistons, they should move evenly. Again, if this isn’t the case, then I know there’s an issue. Normally while the pistons are out as far as they can go, I give them a more thorough cleaning.


Yesterday I got the pistons out again. I removed the calipers, added a piece of flat metal in between the pads, and pumped the brakes so the pistons would come out. I gave them a thorough cleaning. That sound just won't disappear.

Another weird thing - the first time the sound appeared I changed the brake fluid. I reverse bled the brakes with a syringe. On the right side, it worked and the fluid went straight up to the reservoir. But on the left caliper, some would come out of the calipers and I'm not sure where( thinking pistons) . It's like something is restricting fluid from coming up. Could it be the hose? or the ABS modulator?

 

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3 hours ago, trikpat said:


Yesterday I got the pistons out again. I removed the calipers, added a piece of flat metal in between the pads, and pumped the brakes so the pistons would come out. I gave them a thorough cleaning. That sound just won't disappear.

Another weird thing - the first time the sound appeared I changed the brake fluid. I reverse bled the brakes with a syringe. On the right side, it worked and the fluid went straight up to the reservoir. But on the left caliper, some would come out of the calipers and I'm not sure where( thinking pistons) . It's like something is restricting fluid from coming up. Could it be the hose? or the ABS modulator?

 

If the fluid is escaping out of the caliper, it might be best to rebuild that caliper. However, it is also possible that the return hole in the master cylinder is plugged or blocked a bit. I'd check that BTW, have you inspected the front wheel bearings and ruled the bearings out?

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Saw the problem few times already :

first of all , new fluid LOT of 

second check which of the pistons it´s seized (may need to clean or worst a full strip/rebuilt)

third the retard valve from CBS system must be clean 

 

also it´s the left caliper with the CBS system

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