I've got a Yamaha XT125X and the rear brake was squeals like a piggy when used.
So far I've done the following:
Stripped the rear brake caliper, cleaned everything with brake cleaner. Cleaned the back of the pads, the anti-squeal shims and re-greased them with copper slip. Cleaned the disc with brake cleaner and a good set of clean cloths.
I reassembled everything and within a week it was squealing again. I was advised to replace the pads with EBC ones, so I did, and cleaned everything again.
Within a couple of weeks the squeal was back, and is loud enough to be heard by friends on their bikes even with helmets on!
So, my question is, what can I do next to get rid of this squeal?
Not familiar with that particular bike James but as a general suggestion, have you checked the disc & caliper alignment ?
Any spacers missing or bearings moved in the hub or sprocket carrier ?
I "think" the "squeal" that you hear is the AIR being forced through the gap between the disc and the pads
Like a small high pitched instrument ?
So presumably its higher pitched and faster at high speeds and lower pitched and slower at low speeds ?
Possible cause could be :-
Is it fixed or sliding and if so does it slide true ?
And if it's fixed is it in the correct position to line up with the disc ?
It could be that the caliper is at a minutely less than, or greater than, a 90 degree angle to the disc, which could mean that the pads are forming a leading edge where they contact the disc
And I can pretty much take it for granted that the disc has tiny grooves in it
(should be able to feel them with a finger nail or jewllers screwdriver lightly slid across the diameter)
So there would be lots of peaks and troughs on the surface of the pad
But unless and until they have mated exactly there will be gaps where no contact is being made
This would also drastically reduce brake efficiency too
(much less braking material contacting the disc)
Is the disc warped ?
(check with a screwdriver at 90 degrees to it, (held firm with hands or gaffa tape) and spin the wheel )
But with a warped disc it might only be a slight warp which doesn't "pulse" the brake pedal (assuming you get feedback through your footwear)
Obviously pad material has made no difference so my best guess is the disc
Is there a significant "lip" on the edge of the disc ?
Maybe it's past it's wear limit ?
Let us know what you find and if you find a cure
What I forgot to mention above is most important
Check thoroughly that NO part of the caliper (inside or out) is in contact with the disc when the brake is applied
You could probably do with a mate to apply the brake while you turn the wheel and have a good look
See if the caliper or its mount is "moving"when it shouldn't
Or NOT moving if it should
Any metal to metal contact usually produces a "squeal"
Apologies for not responding sooner, been getting in a bit late from work. Thanks for the very detailed description of what could be wrong.
Had a good look at the rear brake today and everything caliper wise is lined up as it should be.
However, when I inspected the disc using my finger nail followed by a closer inspection using a lamp and a magnifying glass, it resembles an old vinyl 45 record with the amount of grooves on it. I'm guessing that some grit must have embedded itself on either the disc or the pads, and then when the brake was used it became similar to grinding paste.
I've used brake cleaner on everything, so I'll give it a go when I ride to work in the morning and see what happens.
It looks like I'll have to get a new disc, and one place advised me not to bother with a replacement Yamaha one as the material is not the best on the world. They advised trying something like EBC discs.
So given that I'm a bit skint this month, it looks like I'll be putting up with the squealing for a bit longer, or use JP's recommendation of don't use it.
Thanks to everyone for responding, it's really appreciated.
All brake rotors will show ware groves after a bit if it's not warped or worn down to it's minimum thickness don't wast your money on a replacement it will just do the same
Thanks to all for the suggestions, however not had chance to check the brakes out yet this week due to working late.
I've also been advised to use wire wool on the disc and take off any grit or impurities that might be on it. Afterwards give the disc a good clean with brake cleaner, including the pads.
probaly no help or relevance james but my yamaha 750 rear brake does exactly the same thing, on the upside frightens the crap out of moronic suicidal pedestrians who walk out in front of me lol.
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