Bolt question

I've got the right bolt and have fitted it (I didn't ride the bike at all with any other bolt in place). Unfortunately, the back brake still doesn't want to play. I've bled it so much that it has effectively had a fluid change, but there's no difference: It still doesn't seem to want to play. I've checked for kinks and cracks in the line as well as flexed the places that don't go straight up, but all to no avail. I've left it overnight in case it was aerated.

I've bled my front brakes before and they work great, but this is my first time doing the rear one. Am I right in thinking the pointy rear brake caliper only has one bleed nipple?

Is there anything else I should check/do before I resolve myself to 2 weeks of riding without a back brake then getting the garage to look at it? Thanks in advance.

Thoroughly cold and sad from working in a freezing, leaking garage without lights for my whole weekend.

[Sid Squid]

When you say it doesn't work, do you mean not at all, or just poorly?

Originally Posted by Ceri JC

Am I right in thinking the pointy rear brake caliper only has one bleed nipple?

Yes.

Originally Posted by Sid Squid

When you say it doesn't work, do you mean not at all, or just poorly?

In terms of braking it's absolutely minute; you can detect a tiny hint of braking, but not enough to be any use whatsoever. Similarly, a lap round the block dragging the back brake does significantly heat up the brake disc. I've dragged a kitchen towel round the disc and there's no sign of contamination of brake fluid/copperslip/brake cleaner, etc.

When you press the lever, there is some resistance (more than just the spring) and the piston moves and you can see the whole caliper move.

I had the rear wheel out (had a new tyre fitted) which was why I was cleaning the brake caliper at the same time. Although unlikely, is it possible that putting the spacers back the wrong way round/anything like that could cause the brakes to be like this? The pads are definately the right way round/on either side of the disc, etc. Perhaps unrelated, but I noticed that the back wheel seems a bit tighter and the bike harder to move round in neutral, although from the looks/sounds of it, it's not caused by the back brake dragging.

I've ridden the bike (albeit only a short distance; I will go for a proper ride tomorrow) and have found that aside from the back brake, the bike feels/handles normally.

Many thanks.

[Sid Squid]

I'd be surprised if the brake could be assembled onto the disc incorrectly, by which I mean I don't think that the spacers could be misfitted and it go back together at all. Are you quite certain that there's no contamination of the disc or pads? Assuming that the hydraulics are functioning correctly, and as you've repeatedly bled them I think we can do so, the problem seems to lie in the caliper's sliding action, and as this is the mechanism that you've recently attended to I'd look there. Remove the caliper and check that, when disassembled, the bits that should slide do so freely. Make certain that bolt in question is a good, but free, fit in the relevant hole, and also ensure that the threaded section into which the front mounting bolt fits is similarly free to move. Ensure the wheel rotates freely with the caliper removed, then push the piston right back into the bore and reassemble the caliper to the bracket, does the wheel still rotate OK? Before pumping up the brake check that the caliper can be moved on it's pins fully from side to side.

Originally Posted by Sid Squid

I'd be surprised if the brake could be assembled onto the disc incorrectly, by which I mean I don't think that the spacers could be misfitted and it go back together at all. Are you quite certain that there's no contamination of the disc or pads?

Re: Pad contamination.

I did get a tiny (and it was only a slight dab) of coppaslip on one of the pad surfaces. I cleaned off as much as I could with a paper towel and used a little bit of brake cleaner on the the pad surface, again wiping off as much as possible with a towel.

I was taught on a bike maintenance course (and my own experience with the front brakes seems to verify this) that a bit of brake cleaner on the pad surface wasn't anything to worry about and it'd soon be removed by the heat once the brake was in use. Is this true?

The only contamination of the disc would be from this pad.

Is there a way to clean the disc, just in case?

Many thanks for the other things to check- I shall have a look tomorrow night over my parent's garage- such luxuries as a roof that doesn't leak, good lighting and infinite cups of tea.

You need to figure out whether it's air in the system or contaminated pads/discs - if the pedal is so soft it goes all the way to the bottom with only a little resistance, then it's air and they need a bleed. If they don't need bleeding you shouldn't be able to force the lever all the way down. If the lever gets properly firm at any point it must be contaminated pads or caliper mounting somehow.

[Sid Squid]

Originally Posted by Ceri JC

I was taught on a bike maintenance course (and my own experience with the front brakes seems to verify this) that a bit of brake cleaner on the pad surface wasn't anything to worry about and it'd soon be removed by the heat once the brake was in use. Is this true?

Brake cleaner evaporates very quickly so I doubt there'd be any left on the pad by the time you'd assembled it, let alone by the time you got to actually use it.

Originally Posted by Ceri JC

Is there a way to clean the disc, just in case?

Same, use brake cleaner, make sure that you remove any brake dust/whatever in the disc holes, a surprising amount can build up in there.

Okay, today I went for a 50 mile ride. I've taken the rear caliper off completely and the wheel turns really smoothly; whatever tightness was there yesterday (after reassembly before the ride) has now gone. I'm confident the back wheel is fine. I've given the rear disc a thorough going over with brake cleaner, even into the holes and I'm sure that's not contaminated now. In taking the caliper off, I spotted something (that I'd not seen in my unlit garage), that there are 3 bevels in the larger (foremost) of the caliper retaining bolts. They appear to be equidistant, which makes me think they should be there, but I thought I'd check. In this picture, the 3rd one is out of shot.



About 4mm down from the top of the smooth section (at the end nearest the thread) there appear to (can't see this in the picture) be gouges running around the bolt, just below where it flares out.

I also noticed when getting the bolt out that after undoing it all the way, it stayed stuck in the hole just rotating when I turned it (without coming further out) and I needed to grip the edge and pull fairly hard it to get it out.

Just thought I'd check this was all normal before I put it all back together as the replacement (new) bolts for both of these should be arriving soon and if there's any chance they could be the problem, I'll wait.

Once again, any comments/observations much appreciated, thanks.

BTW Whilst at Halfords getting some more brake fluid (in case it needs bleeding again), I picked up a model Hayabusa to assemble. Thought I'd keep my hand in while I wait on parts.

[Sid Squid]

By bevel I take it you mean the three flatted off sections on the plain portion of the bolt, and yes, they are a common feature of such pins.
The bolt/pin in question should be a good, but easily sliding, fit in the caliper bracket, if it's stiff something is amiss, check that there isn't any corrosion or debris in the hole and grease it with rubber grease so as not damage the boot, make sure the boot isn't misfitted and in some way dragging on the pin.

Originally Posted by Sid Squid

By bevel I take it you mean the three flatted off sections on the plain portion of the bolt, and yes, they are a common feature of such pins.
The bolt/pin in question should be a good, but easily sliding, fit in the caliper bracket, if it's stiff something is amiss, check that there isn't any corrosion or debris in the hole and grease it with rubber grease so as not damage the boot, make sure the boot isn't misfitted and in some way dragging on the pin.

Thanks very much for clearing that up on the bolts, I'll check the hole now.