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[Closed] Help/Advice - Disc Brakes

 DJ
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[#3027509]

Hi All,

I have been having some issues with my brakes over the past few months but can't get to the bottom of what is wrong with them. The problem is with the rear.

I noticed a few months back that the rear brake was hardly working and I'd only recently had a new pad. I thought it needed to be bled so booked it in to my local shop for them to look at but that didn't seem to make any difference. They then stuck a new pad on and roughened up the rotor which seemed to do the trick for a couple of rides but now I am getting the same thing again.

I'm literally touching the handlebars with the brake lever when I pull it now, with little or no bite. Oddly, they only seem to work when they are wet! Any idea's what's up with them? I'm starting to think I may have to replace the rotor or whole brake unit?!

I'm pretty clueless when it come to bike maintenance so any help would be appreciated.

Cheers


 
Posted : 08/08/2011 9:28 am
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it's impossible to say for sure without looking at them...

but, i've got a few guesses/suggestions:

if you can pull the lever to the bar then it does sound like there is air in the system, and the brake needs a bleed.

bleeding brakes can be tricky and time consuming to do well, if you paid a tenner for the job then you got the trainee for about an hour, i'd be very surprised/impressed if the lad did it well.

you say the brake seems to work better in the wet... i'd guess that's because your tyre has less grip in the wet, and it's easier to lock the wheel.

what brakes are they? and where do you live? - if it's shimano, and you live in sheffield, i'll do it for a pint.


 
Posted : 08/08/2011 10:17 am
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As above, if the lever is pulling back to the bars then the most likely option is you still have air in the system.

Other alternative - it could be a seal issue at either the master cylinder or calliper piston.


 
Posted : 08/08/2011 10:35 am
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Take it to a different shop and ask them to explain what is/was wrong with it.


 
Posted : 08/08/2011 10:57 am
 DJ
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ahwiles - thanks mate but I live in Somerset so just too far to go! The brakes are Shimano M575's.

I shop I took it to is normally does an excellent job so it's a little odd. The mechanic there really knows his stuff but this issue just seems to be ongoing!

With it working better in the wet, and when you spray the brake with water, then that is odd. There just seems to be more purchase from the pad to the rotor when they are wet!

I used to have slightly wider cheap pads on so I'm wondering if that has had an effect?


 
Posted : 09/08/2011 8:55 am
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You might have more than one issue here. The lever pulling back to the bars will not be pad related but you might have oil or grease contaminated pads.

I've bled a couple of sets of Shimano recently including M575's and once finished were very firm at the lever once the free play was taken up.


 
Posted : 09/08/2011 9:55 am
 DJ
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neninja - thanks mate, I will mention what you said to the shop and hopefully they will find something.


 
Posted : 09/08/2011 11:21 am
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Another thought crossed my mind. Are the pads quite worn? Is there a lot of free play before the pads contact the disc? Have a look to see how far the pads are off the disc when not applied.


 
Posted : 09/08/2011 1:11 pm
 DJ
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I'll have a look when I get home mate. Thanks. Lots of sensible suggestions.


 
Posted : 09/08/2011 2:06 pm