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Re: brake and discs problems
NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.
Hello, just got Orbea sherpa back from service
and has already started spontaneously locking up in the rear brakes, very sketchy when
going full pelt down hill plus front wheel screeches :S im guessing that is a bent disc?.
Apart from taking it back and demanding a re work, is there any simple ideas/ tips that may
tell me what the issue is and how to remedy it.
similarly its a first time service at cycle sport thornleigh, at the moment dont recommend it
cheers jeremy
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bent disc *possibly* may be the issue at the rear, but if the disc is "grabby" at some point in the wheel rotation, you have a different problem.
I've had this issue with two tektro discs (both the discs on my first-ever mtb - a mongoose) and one Shimano XT disc, on a secondhand wheelset I bought. If the brakes feel "grabby" at some points in the wheel's rotation under firm braking, it is almost certain that the disc is not of uniform thickness all the way around the circumference, and you need to push the shop for a replacement. Tell 'em the disc has "high spots". Simply truing the rotor won't solve the issue. It is a manufacturing fault.
Replacing the disc solved the problem immediately each time for me, even without the disc being perfectly straight/true.
Screechy brakes are usually a result of having had oil or some other workshop contaminant spilt on the pads, unless the issue manifests in the wet, in which case the problem is common to most hydro disc brakes and that's the way it goes until the weather dries out. If it doesn't go by the end of the ride, after you've given the brakes a good couple of burn-in runs braking hard downhill from speed to bed in the pads, it might be the subject of a conversation you need to have with them.
It pays to be able to service your bike yourself. Good workshops cost top dollar, ordinary ones cost you even more in substandard work and safety risks.
I had this once and was easy to fix. pistons need wiping around the circumference with a light oily cotton bud( pads out of course) and work them in and out a couple of times. hope this helps.