Right brake slightly binding

[kramdra]

Cbr6 2002 with Oe nissin 4 pot callipers. The front has had new discs, pads, callipers rebuilt and new fluid. Right disc and calliper are running hot - both around 50 degrees. Pushing the bike I can hear the right is rubbing (constant, no pulsing, it is not warped). Couple miles at slow speed, or 30 miles at high speed, its about the same. While the left disc is getting warm, the calliper stays cold, and is how I would expect it.

Previously (worn discs and pads) it would stay fairly cold unless I had just been doing hard braking.

Will this go away as the pads and disc wear in? Or have I got a fault somewhere - blocked master cylinder or such..

[Grubscrew]

A dab of silicone grease on the seals helps with the backward travel of the brake pistons on assembly
Did you scrape out any of the crud that gets trapped in the seal groove of the caliper, I’m sure you would have .
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FJR1300/CBR1000F

[Bhud]

With a blocked return hole in the master cylinder, both sides would be affected, so I doubt it's that.

From what I understand, it's the lip on the piston seal that very slightly flicks back the piston when you release the brake. This won't work properly if there's an obstruction (e.g. some dirt around the piston or seal, or a scored/nicked piston). Another cause of this problem may be hydraulic brake fluid that's no good because of molecular changes (e.g. it's old or got too hot once). There is also the possibility that you may have air in the right brake or in the brake line from the right brake up to the junction. Finally, old rubber brake hoses can do this, especially after they've been clamped with mini molegrips (developing cavities along the inside which misbehave irregularly).

It was more than one of these things on my project bike. It started as mild binding (still passed the MOT) and very quickly developed into an unusable and dangerous condition that threatened the disc with warping. Never pinned down exactly which faults it had, but by the time it was fixed, I had replaced all the brake lines, the master cylinder, the brake seals and flushed the brake fluid.

[MCN]

Look at most likely causes.
Shite build up in the pad slide areas. Old brake dust can bake to resemble metal.
Brake cleaner alone won't shift it and it needs a file or an old flat screwdriver to remove it.
Then a slight smear of an anti-seize copperslip molybdenum disulphate (or whatever it's real name is) paste. Sparingly as it can creep onto pads.
Wrong brake pads or incompatible pads. Metal backing plates do not have any clearance to slide freely.

If you've changed pad compound then it's prudent and recommended to remove the old pad residue from the surfaces of the discs too. Not a joyous or satisfying task but it will help your new pads to perform better.
Needs a few sheets of wet or dry.
I jacked the wheels up and drove the wheel around using my drilling machine and a buffer pad.
Don't go mental with the rpms your guaranteed to catch your fingers then.
You should bed in the new pads too. Needs some moderate braking to warm up the pads and the discs.
Then hammer the brakes a few times to melt the material onto the discs.
If you can't resolve the binding issue then postpone the bed in.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[kramdra]

Has not resolved, calliper still getting hot. need to look at it today. I will pump pistons out, push back, see if one is sticking. Could test with worn pads and the pistons further out..
Everything was 100% clean, took fucking ages.red grease on dustt seals and assembledd with brake fluid. Worst case I will clean up the old calliper and swap it.

[RhynoCZ]

I bought a bike with bent caliper once. With the old pads the brake worked fine, as they were adapted to the condition, but the moment I put fresh pads in, I had a problem.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Tankie]

Strip down the caliper properly, remove the pistons and seals, clean out the grooves the seals sit in.
This is normally the problem, corrosion buildup behind the seals, causing them to be compressed too tightly. If the seals are in good order refit with red Lockheed grease.
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Always learning, everyday is a school day

[MCN]

[kramdra]

I always strip, clean and rebuild callipers when replacing pads. I never push dirty pistons back into the seals. They had just been rebuilt. Done 300 miles since.

There is a slight heat scoring mark on the disc, and small area of heat marking pea sized area of pad. Perhaps pads are not flat, visible that most of the pad has not bedded in yet.

Pumped pistons out, cleaned, pushed back in -this reveals any stiff one, but all the same. Repeat a few rimes, applying some red grease. Noted that spring clip was not sitting square and may be restricitng pad movement. Noted ebc pads are plasma cut, the edges are not square, possibly rubbing on calliper and not allowing spring clip to sit nicely. Ground edges flat. More clearance now.

Will test ride in a bit..

[kramdra]

No fucking luck. Right calliper is still binding and getting hot. Looks like I spend tomorrow rebuilding the spare. I will do another test, Ive swapped pads for some nissins that are getting close to wear limit, therefore pistons will be further extended.

[Pete.]

[kramdra]

... It has already been done. The callipers are also annodised and had no corrosion. I do this yearly, and never push dirty pistons in, so the seal grooves were very clean anyway. I then cleaned seals in brake fluid, inspected carefully and reinserted.

I must be missing something. Callipers never usually get hot -discs do, but shouldnt transfer to calliper. Not this quick. It doesnt transfer normally when really abusing the brakes.

I will service the spares and swap asap.

[Tankie]

Go back to the master cylinder, ensure the piston is backing right off and all the orifices in the fluid are clear and clean.
____________________
Always learning, everyday is a school day

[Bhud]

If I read you correctly, then you're reusing old seals. Piston seal gone bad? Seal put in facing the wrong way?

[kramdra]

Done 70 miles with the old pads. There is still some balance issue with the right doing more. Right disk is getting slightly hotter, but calliper much less. Perhaps 40c right, 30c left. With new pads, right was getting 60c, with no differwnce after hard braking or no braking.

Suspect disc is distorted - will get indicator set up and measure it - any suggestions best way as nothing for mag base?
Or, new pads are convex, causing high spots to stay in contact.

Seals are not sided. The groves are cut with a taper so that they sit at an angle. Doesnt matter which way the seals go in.
Master is clean. While I have no stripped it, fluid returns easily (unlike rear master!). It reverse filled with ease, and pistons push in with ease -without pushing surrounding pisons out.

[weasley]

I'd imagine you'd feel a pulsing or judder if the disc was warped. To check runout on mine I mounted the dial gauge to the fork leg using a series of lab stands (metal rods with 90° clamps). Both discs were warped - one I managed to 'straighten' with a large adjustable spanner. The other would not take it so I replaced both.

How is the caliper mount/alignment?
Are the calipers fed by individual brake hoses from the master or by a single line split two ways?
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[kramdra]

Im thinking it is lateral runout, with braking effort swapping side every 180 degrees. May be able to fix by rotating disc on wheel. The mounting faces had slight burrs and corrosion which I cleaned up with a file. Doubt its enough to make a difference, but it will be easy enough to measure and fix.

[Tankie]

Now the disc rotor has got very hot ,has it dished, distorted , use a straight edge to check.
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Always learning, everyday is a school day

[sickpup]

[Bhud]

[kramdra]