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Old 01-09-2011, 06:51 AM   #1
DeeGee OP
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Front Brakes Sticking

My bike failed it's annual MOT last week on a few things one of which was the front brakes sticking.

I've taken the pads out and cleaned the calipers fully with muc-off and a small wire brush. I've given the pads a good clean also and applied some copper grease, but the wheel is still sticking slightly. The wheel will only turn maybe half a revolution before coming to a halt, any ideas or tips on how to free them off??

TIA guys

DG
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Old 01-09-2011, 12:19 PM   #2
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sounds like the pistons are not going back in properly. Your best bet will be to take them out all together and put back together. Maybe the oil rings have swelled a little. I would change them if it were me and then fresh oil and re bead the system. If not it could be your wheel bearing binding when the axle is nipped up.

Just my 2pence.
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Old 01-09-2011, 12:29 PM   #3
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Try cleaning the pistions with out taking them out. Pump them out beyond their normal travel and clean them with brake clean solvent. Then push them in and pump them out several times. Check that the pistions retract slightly when you release the lever.

The master cylinder cap can also cause presure build up and do the same thing. Remove the cap and make sure the small vents are not blocked.

Also, the calipers must slide on the supports. The pistons are only on one side,so the housing must slide over to contact the other brake pad. Very often the grease on these mounts gets hard or the rubber covers swell and make it stiff. After you remove the pads, you can slide the housing off of the mounts. Clean every thing and re-grease.

I'll bet on the dirty caliper mounts.
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Old 01-09-2011, 12:50 PM   #4
marcwestbmw
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You sure it's the brakes? Is the axle torque properly?
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Old 01-09-2011, 02:43 PM   #5
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Cheers guys

Axle was the right torque, I'll take the calipers off and give them a much more thorough going over.

Thanks.
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Old 01-13-2011, 11:41 AM   #6
Hipster
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I had the same issue on my LC4 with the rear caliper, it was due to contamination on the pistion and seal area. The cost of the KTM brake rebuilt kit was pretty reasonable.
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Old 02-09-2011, 02:29 AM   #7
Hockenrider
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Front Brake Calipers

Quote:
Originally Posted by DeeGee View Post
My bike failed it's annual MOT last week on a few things one of which was the front brakes sticking.

I've taken the pads out and cleaned the calipers fully with muc-off and a small wire brush. I've given the pads a good clean also and applied some copper grease, but the wheel is still sticking slightly. The wheel will only turn maybe half a revolution before coming to a halt, any ideas or tips on how to free them off??

TIA guys

DG
Hi Guys ,

Just went to do a change and service on the front end and found the faces of the caliper pistons cracked and damaged starting in the centre.

It looks like a bakerlight or something that could take the heat away maybe on this face which pushes the pad towards the disc- rotor.

Anyone else ever seen this or know why one side has only done it ,

P.s. Just done 30000 km mainly off road 990 ABS model .

Cheers
Holmesy
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Old 02-09-2011, 03:02 AM   #8
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Originally Posted by DeeGee View Post
Cheers guys

Axle was the right torque, I'll take the calipers off and give them a much more thorough going over.

Thanks.
I don't know how the MOT is performed, but when you have the wheel off, it would be good to examine the bearings before doing anything else, especially when there's a problem with the wheel not turning freely. Clean the axle, apply some grease, slide it through and give it a good turn. Everything ok? Now check the axle itself, that it's not deformed. Roll it along an even surface on a clean sheet of paper. Axle deformation is pretty rare to my understanding on bigger bikes but could happen.

You did not mention when the brake fluid has been changed. If the problem is with the fluid been contaminated(moisture or foreign material), changing it will help with the problem, but it is time consuming to determine whether it was the fluid, so before doing anything I would try to see if the problem is with the pistons. Pumping them beyond their normal travel, cleaning, and bushing them back might help as suggested above. This will get you through the MOT but the problem persists and a rebuild is along the way. Before installing the brake pads, the pistons SHOULD pretty much move with finger force, but I'm yet to manage to move them properly even on a new bike without the help of some kind of a tool.

On Super Dukes the brakes sticking is a common problem, but I'm not aware if it is so with the Adventure also(presuming this is Adventure were talking about here).
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Old 02-09-2011, 04:44 AM   #9
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I stripped and cleaned the calipers and pads three times before I was happy. Thanks for the comments and advice.
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Old 02-09-2011, 05:03 AM   #10
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Quote:
Originally Posted by Hockenrider View Post
Hi Guys ,

Just went to do a change and service on the front end and found the faces of the caliper pistons cracked and damaged starting in the centre.

It looks like a bakerlight or something that could take the heat away maybe on this face which pushes the pad towards the disc- rotor.
Seen the same on my bike. As you say, the inserts in the pistons are to lessen heat transfer into the brake fluid.

One of the inserts on one of my front calipers has a small hole in it, I assume a tiny stone got in there or something. Doesn't seem to have any adverse effects, so I've just left it.
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Old 02-09-2011, 05:13 AM   #11
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No one mentioned just cleaning the guide pins. I've found all of my sticking issues were related to the pas slide pins. Not the caliper pins, but the ones with the funny shaped circlips. Wirebrush those off and grease them an see what that does for ya
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Old 02-09-2011, 07:44 AM   #12
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Dee-gee, put on a slightly worn pads just to get you through your MOT, its a bastard to have to keep going back to them. The thinner pad will let the piston run in a clean and fresh spot on the seal, allowing it to return fully. Then when its pissing down with rain and you dont want ot ride, strip it all down and check for wear in the bore of the piston cylinder. I'm sure there is a re-build kit out there, if there is I'd throw it in there while you can see it all. Also, when you put your front axel in, push it in to almost flush on the right side of the bike, then tighten that clamp, with the wheel spinning, gently snug up the axel nut till the rotors are centre in the calipers. Tighten the final clamp. If there is any wobble, slop, or it just doesnt spin, you should replace your bearings, seals, and spacers. There are a fair amount of variables that you can change to adjust how the rotors line up in the calipers.

Good luck, and if you get a chance head to Rivington Pike on a weekend.
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Old 10-06-2013, 01:07 PM   #13
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digging an old thread back.

Searched a bit and could not find much info, apart tips on how to bleed the 990 Adv ABS brakes.

Long story short, the front callipers are sticking (both). If i push each caliper in (by hand), the pistons will retreat a bit and the wheel will rotate freely. As soon as the front lever is squeezed, (1 or 2 times) the brakes become sticky again and the wheel wont rotate freely.

As if the pistons wouldnt retreat as necessary, but a small push by hand will make them go quite easily.

Also adjusted the lever for the highest slack thus making the master cylinder going in the least (just for testing purposes). No significant changes.

Fluid reservoir seemed a bit too full, fluid is clear, removed 10cc's, no change.

Any suggestions before taking the callipers/pads out for brushing and re-bleeding?
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Old 10-06-2013, 03:48 PM   #14
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Start doing what Zuber said above- cycle the caliper pistons beyond their normal range both out and in, by taking the calipers off the forks (or taking the front wheel off) and pumping the brakes, then pushing the pistons all the way back in, then pumping them out again. This will often make brakes perform a lot better, as it helps clear out the gunk that the piston seals can get stuck in, making the caliper either stick or not grab fast enough.

You'll have to do this slowly and carefully in order to keep the right amount of fluid in the master cylinder reservoir, adding some when you pump the lever, and taking some out when you push the pistons back in.
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Old 10-07-2013, 03:49 AM   #15
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I just got new tyres and only when putting front wheel back on I noticed it did not spin freely.

Am I right in thinking that it should spin with NO drag from the callipers?
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