Jump to content

Disc Vibration / Shudder


Lounge Lizard
 Share

Recommended Posts

Anyone got some advice please !

 

After about two hours ride (during the vigne a vigne) my back disc started to shudder on a steep downhill. I tried various ways to figure out what was wrong but nothing made sense.

 

- Even when I did not brake at all, the shudder started as soon as I got upto a good speed on a the bumpy dowhills.

 

- On flats (or on the downhill) etc where I am pedaling - it stopped.

 

- I could stop the shudder / vibration briefly by locking the back wheel, but it starts again a couple of seconds later.

 

- As I say - it even started without braking - and somehow stops if I start pedaling hard again.

 

- I had the same happen a few weeks back, then it suddenly stopped one day and I forgot about it.

 

- I changed pads recently.

 

- I don't know if its relevant, but I have a problem with spongy feel on the brake leaver - and have bled the fluid - but somehow I eventually - after much pumping - get a bubble again showing in the bleeder tube, so I do think the brake fluid still has some air in. Possibly a seal problem. (Anyway the brakes work fine - so not too sure about the air)

 

- I think I can feel a little play in the wheel bearings.

 

- I even thought the disc or pads could be overheating - and tried a squirt of energade - lots of steam - but it did not stop the problem just added a squeal (sounded like a duck being strangled)

 

- As mentioned - the problem only started after about 2 hours, so I don't think it was due to not 'settling' /breaking-in the new pads.

 

HELP !

  
Link to comment
Share on other sites

 

Sounds as if the discs & pads are just overheating... common problem with bottom end discs and pads, but one that can generally be sorted by getting a new, more heat efficient disc.

 

Just think - you're on the brakes for, let's say 50% of the race. That's an hour on the brakes, at what i presume was a very high pressure. Just think how much heat that would be putting through the system. Just the fact that steam emanated from the discs when sprayed by your energade should tell you that much.

 

Either that, or just spend less time on your brakes! Wink

 

Good set of discs can be bought for around R 300 (for Alligator windcutters - see pic) or more expensive ones can be upwards of R 300 per disc. But then you pay for what you get... a good disc with great heat dissipating properties...

 

Don't let the low price of the Alligator discs fool you though - they are very good! Just make sure that if you're upgrading, you get a set of Metal Sintered brake pads, as any normal resin based pads would be ripped to shreds on the Alligators or any other "top line" disc. Plus, they're FAR better at dissipating heat, and will last much longer as well...

 

As par as sponginess goes, it's par for the course for a low-end brake system. Also doesn't help the cause if the brake system overheats, because the fluid then boils and can cause the sponginess for obvious reasons... fluid becomes less viscous (more runny)

 

I am assuming that the brakes are a low-end system... but then shuddery brakes generally boil down to the same thing. Overuse, and overheating. (please excuse the pun) 

 

 

 

Link to comment
Share on other sites

Headset, fork bushings, rear suspension bearings/ bushings/ hardware, wheel bearings, bottom bracket bearings is where I would start looking. If the problem persists when you are not on the brakes its most likely elsewhere and perhaps extenuated by the brakes.

Link to comment
Share on other sites

You've answered your own question by saying there's play in the wheel bearings, like Morewoodkid says start there and then worry about the brakes, highly unlikely as well - if the spring has some how gone missing from between the pads then the pads could be rattling around also causing the vibration.

 

You dont say what brakes you have as each has their little traits...

 

Start with the wheel bearings...once you've finished with those check all the spokes are tight, all relevent bolts are tight etc...
Link to comment
Share on other sites

Ok, sorry to labour this issue, but I'm going to hi-jack this thread (if you don't mind Wink) because I have a very simmilar problem...

 

Problem:

When I use the front brake hard it squeals for about 2 seconds before the squeal "resonates" and causes the whole bike to shudder (quite violently Shocked).

 

I first checked that the wheel was in properly and secured.

Then re aligned the pads (pretty new, no significant wear)

Then checked that the headset, and brake mounts etc were tight and no play in the front wheel, and removed and retightened the rotor.

 

Then I read a post the other day similar problem and ppl advised that the person lightly sands the rotor with fine paper to clean them. I tried that last night eventually, and half way to work this morning was fine (yay Tongue), and then it started again (ah Cry).

 

I dont know how to check wheel bearings, although the wheels were serviced a month ago, and the shock 2 months ago.

 

unlike the OP it does not occur during normal riding, only braking.

Its not over heating issue, because it occurs even on first use onwards...

 

Brakes are XT, pads are XTR metal sintered.

 

I really dont know what else to try...

 

Link to comment
Share on other sites

 

Ok' date=' sorry to labour this issue, but I'm going to hi-jack this thread (if you don't mind Wink) because I have a very simmilar problem...

 

Problem:

When I use the front brake hard it squeals for about 2 seconds before the squeal "resonates" and causes the whole bike to shudder (quite violently Shocked).

 

I first checked that the wheel was in properly and secured.

Then re aligned the pads (pretty new, no significant wear)

Then checked that the headset, and brake mounts etc were tight and no play in the front wheel, and removed and retightened the rotor.

 

Then I read a post the other day similar problem and ppl advised that the person lightly sands the rotor with fine paper to clean them. I tried that last night eventually, and half way to work this morning was fine (yay Tongue), and then it started again (ah Cry).

 

I dont know how to check wheel bearings, although the wheels were serviced a month ago, and the shock 2 months ago.

 

unlike the OP it does not occur during normal riding, only braking.

Its not over heating issue, because it occurs even on first use onwards...

 

Brakes are XT, pads are XTR metal sintered.

 

I really dont know what else to try...

 

[/quote']

 

Brake squeal, is brake pad dust on the pad, that causes the pad to " shudder" at very high speed, causing the squeal.  Same as a cars brakes squealing.  It has nothing to do with the disks, simply brake dust.

 

Certain pads do it more than others

 

Link to comment
Share on other sites

 

Ok' date=' sorry to labour this issue, but I'm going to hi-jack this thread (if you don't mind Wink) because I have a very simmilar problem...

 

Problem:

When I use the front brake hard it squeals for about 2 seconds before the squeal "resonates" and causes the whole bike to shudder (quite violently Shocked).

 

I first checked that the wheel was in properly and secured.

Then re aligned the pads (pretty new, no significant wear)

Then checked that the headset, and brake mounts etc were tight and no play in the front wheel, and removed and retightened the rotor.

 

Then I read a post the other day similar problem and ppl advised that the person lightly sands the rotor with fine paper to clean them. I tried that last night eventually, and half way to work this morning was fine (yay Tongue), and then it started again (ah Cry).

 

I dont know how to check wheel bearings, although the wheels were serviced a month ago, and the shock 2 months ago.

 

unlike the OP it does not occur during normal riding, only braking.

Its not over heating issue, because it occurs even on first use onwards...

 

Brakes are XT, pads are XTR metal sintered.

 

I really dont know what else to try...

 

[/quote']

 

What rotors you running? I have heard of this issue on certain centre-lock rotors where there is a small amount of play developed over time between the rotor spline and hub.

 

Alternatively try a different pad compound, its quite well known that the Sintered Shimano pads are noisy ;)

 

 

 

Link to comment
Share on other sites

Ok, sorry to labour this issue, but I'm going to hi-jack this thread (if you don't mind Wink) because I have a very simmilar problem...

 

Problem:

When I use the front brake hard it squeals for about 2 seconds before the squeal "resonates" and causes the whole bike to shudder (quite violently Shocked).

 

I first checked that the wheel was in properly and secured.

Then re aligned the pads (pretty new, no significant wear)

Then checked that the headset, and brake mounts etc were tight and no play in the front wheel, and removed and retightened the rotor.

 

Then I read a post the other day similar problem and ppl advised that the person lightly sands the rotor with fine paper to clean them. I tried that last night eventually, and half way to work this morning was fine (yay Tongue), and then it started again (ah Cry).

 

I dont know how to check wheel bearings, although the wheels were serviced a month ago, and the shock 2 months ago.

 

unlike the OP it does not occur during normal riding, only braking.

Its not over heating issue, because it occurs even on first use onwards...

 

Brakes are XT, pads are XTR metal sintered.

 

I really dont know what else to try...

Sounds like pads are glazed. Maybe the compound is cooked now and thats why it keeps doing it after deglazing. Try put new pads. if the problems goes away you know it's not bearings or something else.
Link to comment
Share on other sites

Rotors are XT centre lock.

 

Been running same rotors for at least 3 sets of sintered metal pads and its the 1st time they doing this, so its not the traditional "noisy". Could mayb be worn rotor?

 

I have a spare set of pads, I can try them. The pads still have plenty wear left in them, so i dont really want to replace them, but at least I can try figure out the problem.

 

@ canaris, Thanks, not much single track on the way to work (plenty on the week end tho), and somehow not breaking while going through busy intersections doesnt sound like such a good idea.

 

 

Link to comment
Share on other sites

IMO the only real way to have silent disc is to have v-brakes or a fixie.  Seems they are always making some kind of noise somewhere Confused

Link to comment
Share on other sites

 

Rotors are XT centre lock.

 

Been running same rotors for at least 3 sets of sintered metal pads and its the 1st time they doing this' date=' so its not the traditional "noisy". Could mayb be worn rotor?

 

I have a spare set of pads, I can try them. The pads still have plenty wear left in them, so i dont really want to replace them, but at least I can try figure out the problem.

 

@ canaris, Thanks, not much single track on the way to work (plenty on the week end tho), and somehow not breaking while going through busy intersections doesnt sound like such a good idea.

 

 

[/quote']

 

Centrelock... + Sintered... = DEVIL

lol, let us know if this sorts your problem out, besides the bragging "I told you so's" which it will add to my status it will also be a good one to remember to assist future hubbers with the same symptoms.

 

I have to give a little plug to my stuff: SERIOUSLY try the Brake Authority "BURLY" ads, if they don't increase performance and reduce squeal after you have bead them in properly I will personally refund you ;)

 

Link to comment
Share on other sites

Thanks for all the ideas guys. I am pretty certain its a heat thing - because it only starts after a lot of downhill (hours into a ride)

.

On a different note - I have seen many web posts/articles that say Mineral Oil and Dot fluid are 'the same' as far as MTB discs are concerned - except that DOT has a higher boil point.  Others say the Shimano 'seals' will be destroyed by DOT fluid. Is this just one of those 'use only origininal parts' warning to make you spend on their stuff only ?

.

Whats the truth - can I use DOT 4 in Shimano Deore system ?

What/where are the Seals ?

Who sells seal replacement kits ?

what do they cost ?

can I fit them myself ?

.

(as you probably could tell from my earlier post - I am old man who generally s....ts himself on the narrow technical rocky single track downhills - so not really in favour of total brake failure)
Link to comment
Share on other sites

Forgot to mention - I have Shimano Deore XT

 

Will I do them (or the rotor) any damage if I pss on them to cool them down ? i.e. will the rotor warp or weaken ?

 

(not mention the smell !!)

 

 
Link to comment
Share on other sites

You CANNOT use DOT fluid in shimano systems only mineral oil (and olive oil doesn't work either contarary to popular belief)

 

The shimano systems are not servicable therefore if the seals go ( VERY rare for this to happen) then replace the component.

 

There is a strong chance that pssing on the rotor will warp it as any sudden cooling will do the same.

 

I doubt very much that the problem is overheating, I'll go with Morewood kid's explanaton of the centrelock rotors as the steel rotor is riveted to an aluminium carrier and with age the rotor can develop play between itself and the carrier. Either that or try fitting one resin pad and one metal pad in the same caliper, it's a trick that the pro's use to get the beat of both worlds...
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

Settings My Forum Content My Followed Content Forum Settings Ad Messages My Ads My Favourites My Saved Alerts My Pay Deals Help Logout