Rear Brake, advice needed urgently (please)

Pottsie

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Chaps

I'm due to head across the Channel on Monday but up against it at the moment.

Yesterday I change the rear brake pads, the old ones were knackered and don't know whether they were OEM or other; I have replaced with EBC.

After 10 miles of riding I pulled up to check all was fine, I had felt the abs come on when I braked a couple of times and found the disc and caliper extremely hot, I mean extremely hot! It dawned on me I had not removed excess brake fluid so went the last mile home and drained it; the wheel has remained free running all the time.

I have then done 5 miles (after allowing all to properly cool) and again it got really hot so I diverted to local bike mechanic shop at 4 pm today and they were brilliant, took of the caliper, cleaned everything again, checked all was operating and rebuilt, free play in brake pedal which was non existent having been increased. Everything perfect.

5 miles up the road without touching the rear brake at all and checked again all extremely hot so returned to mechanic (now 5.15) and he checked it over and agreed it seemed excessively hot but that there was absolutely no binding or other problem evident. He suggested riding it a bit more and using the brake to see if just a bit of use settled things down. 5 miles to home and using brake as normal up on centre stand and disc and caliper ready to cook eggs but wheel spinning absolutely freely and operating correctly,

Has anyone experience this themselves and did you find and answer? It would bloody well be bank holiday and so can't even take it to a dealer to sort/check. Was thinking of popping pistons out to clean them (but theyboth run freely anyway) but I see according to the manual abs brakes require the dealer and their tools.

Don't really want to cancel holiday (two weeks of riding in Europe) but want it to be safe particularly as wife on back.

Any genuine knowledge or experience would be very gratefully received.

Thanks

Martin
 
Don't forget that front brake also activates rear too.

Assuming that nothing is sticking caliper wise, you are left with either a faulty master cylinder or not enough clearance at pedal.

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When you say took off he caliper. Did they actually remove it from the mount that it slides on to clean a re-grease the sliders. Could be sticking on those. Are the pistons pushing in nice and easily and pumping out freely again.2 things you can easily check yourself in a few minutes.
 
Thanks for advice

Yes its ABS

Pistons and floating caliper appear to move fine, free play in pedal exists because mechanic put some in but there was none before and its not a lot now so will increase that

I have just been asked about front and brake link, seems ignorant of my own bike but I didn't think they were so that's useful ta

I am going to get up early and start again, will clean everything off and see check through, increase free play and try it, otherwise might stick old pads in as experiment.

Many thanks chaps - stress I could do without tonight!
 
Have a full working brake system available if you're really stuck and if you needed to swap anything out.
Am in Rochester so possibly on your way to Folkstone, if that's the way you are going

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just make sure nothing is tuching thefront brake lever. Mind you itsa bit too much of a consistence. JJH
 
In case of use, a few things to mention. Other have already said that front lever applies some rear via linked brakes. Do you think caliper is hotter than normal, or has it not previously come up?

Worth checking systematically to see if there is a problem or not. Spin rear wheel, apply foot brake, check wheel stops. Spin wheel again to check brake is releasing when pedal released. Repeat.

The do same with hot rear caliper. Ride bike making sure to use rear brake, put on centrestand etc....

Once caliper cool, ride a few miles without brakes, eg on dual carriageway etc, then use engine braking to slow and check rear wheel is spinning and caliper cool.

If you do all that and everything is as it should be, heat is almost certainly form normal use. If I use rear brake a lot, caliper gets too hot to hold. Harder to make fronts get as hot as they are 4x the size of rear.

In terms of possible problems, excess fluid is one, but I have had a warped disc in past (when flange replacement done on recall) and went through process above to work out that rear was getting hot when brakes not used at all (neither front nor back). BMW sent me new disc and problem disappeared when fitted. Had to infer issue as didn't have decent DTI
 
Don’t know what year yours is but if you have Enduro Mode will it allow you to turn off ABS to the rear wheel? Shot in the dark but it might make a difference :nenau
 
Mulcher said:
Don’t know what year yours is but if you have Enduro Mode will it allow you to turn off ABS to the rear wheel? Shot in the dark but it might make a difference :nenau
Click to expand...
Hexheads are too early for that, even if he did switch the abs/asc off the brakes are still linked.

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You say after it originally overheated you drove the last mile home and drained it. Did you remove the excess fluid from the reservoir or at the bleed nipple?

I was thinking you may have originally boiled the fluid in the caliper and introduced air into the system somehow.:nenau

It seems strange it was working fine before you changed the pads, and if the disc is heating up, the pads must be binding or the rear brake is coming on when you're driving.

Maybe you could try cracking the rear bleed nipple open with the bike switched off and no brakes applied, just to see if there's been any pressure left in the system.

Just my thoughts, hope you get it sorted. :thumb2
 
Right everything considered as per your help, and adjusted where necessary. Got back after 25 miles, wet tea towel on disc to get hissing as couldn't touch it, also caliper untouchable. That said wheel span freely and brake operated correctly with instant wheel release when pedal released. Ridiculously hot though. What I have noticed now having cooled it and removed the new pads is that the thickness of the braking surface on the piston side pad is about 1.8 mm thicker than on the other side, not through wear in their short use but as produced. I'm presuming this is normal but I haven't anything to compare it with.

The stress goes on! I almost think if it isn't binding in 25 miles there has to be a limit to how how it can get - the disc doesn't show signs of friction or wear but I feel is bluing slightly. Always on a Bank Holiday!
 
Could it possibly be heat generated in the final drive transferred to the rear brake disc, or is this not possible

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EBC pad on piston side is thicker as wear rate higher that side.

If wheel spins freely after brake application, even when caliper hot, then heat is likely from normal brake operation.

Have you ridden bike, toes on footpegs (to rule out right accidental application), without using brakes, and then checked caliper?
 
Thanks for confirming about pads, just went to a bike shop to check against others and that the same. Used old pads going there and back and disc and caliper extremely hot still so I am assuming it may be a piston sticking although they both come out and push back in easy enough. When coming out the one only starts to move when pressure is applied to other piston, would that suggest one sticking, would you expect both to move together (when off disc).

Incidentally when I say it gets hot I'm mean put a damp tea towel on it and you get hissing, the pads themselves look blue as well. Not great!

Not sure you can pop out the pistons on these as they are solid fronts not hollow like others, my mate has the device to help bleed them if necessary just not sure how to get piston out.

Wife on check the travel insurance and cancellation policies!
 
Would like to help, but can't keep asking same questions. Here is a recap. Need answers to all of these

1. Is your observation that caliper is significantly hotter than it used to get, or that caliper is very hot without any comparative data points?
2. Did you test rear wheel spins freely after getting caliper hot?
3. Have you ridden bike whith cool caliper to start without using brakes and using engine braking to slow? This is key test which is why I keep asking. Even round the block. Round a park. Anywhere without traffic that allows you to use engine braking safely
4. Did you keep toes on footpegs above to make sure no possibility of accidental activation?

You need to go through conditions under which brake getting hot before finding other hypotheses. And don't mistake your own susprise at something for that thing being abnormal - its not the same thing.
 
Stand in front of rear brake caliper. Hold bike subframe. Place foot on rear caliper and push hard. The pistons will retract and the caliper will slide open on its two pins. Then pump rear brake pedal Do this a few times and it should free up any sticking pistons or caliper pins. All owners should do this every couple months anyway as a matter of course and as it acts as preventive maintenance in keeping the caliper from seizing on its sliding pins.
 
Because the rear calliper only has a sliding pin at the extreme of one end and is a single sided piston mechanism rather than opposing pistons, there is a large bending moment every time the brakes are used. This causes the pad nearest the pistons to wear faster, and can also resist pulling the non-piston side inwards due to the bending moment applied.

The sliding pins are prone to wear and sticking, as are the pistons.

I regularly unbolt my rear calliper from its mount and clean/regrease the sliding pin, clean around the piston skirts then use a small G-clamp to press the pistons fully home and have another clean. Finally reassemble the calliper and pads then pump out to contact the disk face.

Steptoes method is quicker, but won't clean the skirts/pistons or lube the pins.
 
Hi, I have the same problem. Did you fing the solution or was the heat normal.

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Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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