mac79
newbie
Reged: 13/04/2008
Posts: 33
Loc: highlands,scotland
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Hi, i am still having problems with this rear brake, i posted previously and had a few suggestions,i have now tried everything i can think of to rid myself of the noise/vibration through the frame.
Spoke to my LBS today on the way home from work,we tried yet again aligning the calliper without any luck!
we noticed a minor warp in the disc,but no worse than the front disc.
Really pi**ed off with this now, at the point where i dont want to ride the bike anymore!
Read last night that some brake vibrations can be caused by frame damage (i.e crack), i cant see any damage,but i do recall a loud crack on a down hill section which i put down to stone bouncing, any truth to this theory???
HELP!!!! 
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gtxxx
addict
Reged: 11/03/2008
Posts: 624
Loc: Scottish Borders
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You could try removing some of the suspension bolts one at a time to inspect for damage to them but you'll need a torque wrench when putting them back in.
GT
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It's not the fall that hurts it's the landing!!!!!
I only fall off to get marks from those watching!!
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MTBLeague
Pooh-Bah
Reged: 23/05/2007
Posts: 2187
Loc: What is normal?
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Jack hammer vibrations, maybe but generally not brake ones, the noise can be unbareable and can drive you nuts, some of us must have suffered this in the past, guess which ones by the posts. 
If LBS has tried alignment twice it cannot be that, move on to somthing else, what else may be loose, wheel/frame bearings pivots etc, is it better or worse under light/heavy breaking, smooth/rough surface, wet/dry conditions, even the pad size inside the calliper.
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The Path of least resistance is easier to follow............ when things are -Back to normal.... ...ish.
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185nick
addict
Reged: 09/08/2007
Posts: 427
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I agree with mtb league. Using a torque wrench check that everything is tight and while doing this inspect frame for damage.
After doing this, if the problem persists, you could try new pads. Other than that I buggered. Is it only happening when you brake?
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185nick
addict
Reged: 09/08/2007
Posts: 427
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Just read your last post and saw that it is happening under braking. Someones suggested in the other post to swap front pads with rear pads, this is a great idea as, obviously, if the problem then moves to front brake you know that it's the pads. Have you checked that yoour QR skewer is tight.
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mac79
newbie
Reged: 13/04/2008
Posts: 33
Loc: highlands,scotland
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been there and tried that guys,bike is a hardtail Giant Xtc sx,pads have been replaced,which made no difference!!!
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185nick
addict
Reged: 09/08/2007
Posts: 427
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Just a thought, bit off a shot in the dark really, but you said the you heard a bang, as if a stone pinged up against your bike. Right my point.... I'm wondering if a stone pinged up and caught the edge of your disc causing a dent, which will possibly create a rough edge on the braking face. As I said, a shot in the dark, but might be worth having a look to make sure the very edge of your disc is free from damage.
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mac79
newbie
Reged: 13/04/2008
Posts: 33
Loc: highlands,scotland
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not a bad theory,i also wondered about rotor damage,ive removed the rotor to clean and inspect refit to correct torque,no damage,as i mentioned there is a minor warp,would that be enough? think i am going to have to change the rotor as a process of elimination
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Sir_Queuesalot
Carpal \'Tunnel
Reged: 05/12/2007
Posts: 6212
Loc: OSMM Survivor - just!
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Gotton a bit confused on this issue, is it catching when you ride along like a skitch skitch sound or just making a noise when you brake?
Also, is it a high frequency noise or a low grinding noise?
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My site www.ezerider.com serving North Staffs & South Cheshire
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rb2000
old hand
Reged: 25/09/2008
Posts: 800
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get a new brake/rotor
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Keep it pinned...
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185nick
addict
Reged: 09/08/2007
Posts: 427
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Quote:
get a new brake/rotor
Could be a bit costly though, when there might be a simple explanation for it.
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rb2000
old hand
Reged: 25/09/2008
Posts: 800
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possibly, but if you've tried everything you can think of, and it really is driving you mad, its a simple solution.
plus its an excuse to upgrade!
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Keep it pinned...
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mac79
newbie
Reged: 13/04/2008
Posts: 33
Loc: highlands,scotland
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Hi Q,
The noise is a mid range groan,there is no rub whilst free wheeling, the best way i can describe it is: freewheeling at about 8mph then gradually apply pressure to the rear brake to come to a stop and the noise and vibration starts! hope this helps.
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fredmundo
Carpal \'Tunnel
Reged: 30/06/2008
Posts: 3896
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I'm sure someone will correct me if im wrong... But it sounds as if perhaps you have got a little play in the hub or your back wheel is not tightened enough... Orsome such thing.
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"Duct tape is like the force: It has a dark side and a light side and it holds the universe together."- Carl Zwanzig
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Rampage
newbie
Reged: 15/08/2008
Posts: 37
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As above, could be.
Is the caliper and dropout on the same piece of frame with no pivots or bars inbetween?
Could you swap front and rear disks or are they different sizes?
Take off the caliper and every bolt/adaptor and clean. Remove pads and give the inside of the caliper and back of pads a clean. Check pistons for damage.
Check the pad return spring for damage.
When you refit, make sure everything is flush, the caliper/frame and frame/caliper.
Clean the disk with IPA or equivilent.
Check rotor bolts.
Check wheel bearings, spoke tension.
Check ALL suspension pivots.
Basically it's something moving, even if it is 0.005mm!
I had a problem with squealing disks, and I was taking them out and sanding down the pads everytime I rode, it turned out that it was the act of sanding the pads that caused the squeal. When I stopped trying to fix it, it went away!
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Rampage
newbie
Reged: 15/08/2008
Posts: 37
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Also, try aligning the caliper by holding the brake on as hard as you can. If that doesn't work, try by eyesight.
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mac79
newbie
Reged: 13/04/2008
Posts: 33
Loc: highlands,scotland
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***FIXED***
Hi guys just an update on this fault,after piss**g about trying to sort this i replaced the rotor and replaced the pads,everything sweet again!!
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Sir_Queuesalot
Carpal \'Tunnel
Reged: 05/12/2007
Posts: 6212
Loc: OSMM Survivor - just!
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Funny, I just found this tech site about noisey brakes...
http://www.formulabrakeusa.com/wp-content/uploads/2009/01/disc-brake-noise.pdf
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My site www.ezerider.com serving North Staffs & South Cheshire
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MTBLeague
Pooh-Bah
Reged: 23/05/2007
Posts: 2187
Loc: What is normal?
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Turkey Gobbling!!!! Isn't that illegal, love that list of noises, do you think moisture may be playing a factor in the UK.
So it was not alignment after all. Don't worry too much about a little noise, mine scream like a banshee untill all the moisture is off them.
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The Path of least resistance is easier to follow............ when things are -Back to normal.... ...ish.
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185nick
addict
Reged: 09/08/2007
Posts: 427
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Quote:
***FIXED***
Hi guys just an update on this fault,after piss**g about trying to sort this i replaced the rotor and replaced the pads,everything sweet again!!
Glad you got it sorted. Now you have to go back to shouting "excuse me please" when you meet ramblers on the trail.
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