newbie on MTB. vibrating rear disc

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newbie on MTB. vibrating rear disc

Postby jeff_o » Tue Apr 30, 2013 12:51 pm

Hi All,

I got myself an old 2006 spec'd FSR XC comp and did a ride on Mt. Annan 2 sundays ago. unfortunately due to my excitement I crashed but it was no biggie except some bruises on my left knee and elbow. Bike was ok except for some mud. luckily i did not hit any hard object except the ground.

I noticed my rear disc makes an annoying squeal when braking and it's because the rear disc is vibrating and resonates to the whole rear triangle. I've cleaned it well and still makes that sound. any ideas?
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by BNA » Tue Apr 30, 2013 1:17 pm

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Re: newbie on MTB. vibrating rear disc

Postby trailgumby » Tue Apr 30, 2013 1:17 pm

I'm guessing the pads are contaminated, the brakes are Avids of some description, or both.

Unfortunately it only takes the slightest hint of grease, chain lube, oil or WD40 on the pads and they're stuffed. Thereafter, lots of noise and not much braking. After changing wheels or removing/reinserting for travel by car, before touching the levers I wipe my rotors down with brake cleaner and a clean rag just to be sure. Trashed a few too many sets of pads :oops: Not much you can do except replace when that happens.

If they're Avids, you can take the view that you'll never get lost because someone will always know where you are :lol:

But if like me you enjoy being able to hear the sounds of the bush, there are compounds you can apply (spray or paste onto) to the back of your pads from motorbike parts outlets that wil mitigate the noise.
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Re: newbie on MTB. vibrating rear disc

Postby jeff_o » Tue Apr 30, 2013 2:31 pm

hi trailgumby, yes you are correct the brakes are avid elixir 1.

lol i guess you know a lot about these stuff!

can I degrease or even soak the pads with coke to remove the oil or sumthin?

what do you call the compounds you can buy in auto shops? or better yet just buy a set of new pads? is aftermarket ebay stuff ok? what do i get? semi metallic, metallic? etc etc?

ta!
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Re: newbie on MTB. vibrating rear disc

Postby trailgumby » Tue Apr 30, 2013 9:19 pm

I've tried all that stuff... degreaser, brake cleaner... in the oven... unfortunately you're up for new pads *IF* they are contaminated.

I prefer to use the OEM metallic pads myself, but then my brakes are Shimano XTs which are a lot more powerful so I can get away with it. If you go OEM, they will at least be no worse than what you currently have.

I'm not sure the name but they are a rubber or silicone-based paint. Do not use the grease-based ones or you'll be back to square one but with a lighter hip pocket. Your local motorbike or car parts dealer will be able to help you. Ask at the counter :)
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Re: newbie on MTB. vibrating rear disc

Postby bychosis » Tue Apr 30, 2013 10:26 pm

If the pads aren't bedded in properly you could try sanding them back a bit, or rubbing on some smooth concrete to take off the top layer. Repeat the bedding in process and try again. I have Avid Juicy brakes and new pads always squealed loudly for the first XXkm of riding until they bedded in properly, often while just riding along. A quick dab of the brakes would fix it for a bit while just riding along. Once they were bedded in the loud squeal stopped but the 'turkey gobble' softish squeal remains as an Avid feature - it's not really annoying to me as it's not very loud.
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Re: newbie on MTB. vibrating rear disc

Postby jeff_o » Tue Apr 30, 2013 10:31 pm

i'll just get new pads. how do you "break-in" new pads? i recall you have to ride the bike and brake softly until full stop for few kms? is that correct?
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Re: newbie on MTB. vibrating rear disc

Postby mitzikatzi » Wed May 01, 2013 8:33 am

jeff_o wrote:i'll just get new pads. how do you "break-in" new pads? i recall you have to ride the bike and brake softly until full stop for few kms? is that correct?


I use Google "bed avid brakes"
finds

2010_avid_technical_manual_english page 56
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Re: newbie on MTB. vibrating rear disc

Postby trailgumby » Wed May 01, 2013 10:30 am

Bedding in: hard braking from moderate speed but rolling out of the brakes before coming to a complete stop, repeated 6-12 times.

I swap wheelsets from time to time and need to repeat this process. Forgot to do it last week and frightened myself ... and then again when I put the first wheelset back on for commuting. Duh! :oops:
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Re: newbie on MTB. vibrating rear disc

Postby celeste boy » Thu May 09, 2013 7:32 pm

jeff_o wrote:hi trailgumby, yes you are correct the brakes are avid elixir 1.


!


I have had this problem with my bike since new and they are those brakes named above. I'm hoping new pads will work.

CB
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