Disc Brake Judder

mtbjunkie08

Hi,

When I'm on a steep descent and have to brake hard im getting a really loud juddering (not squeal) from my rear brake. I've only had the bike about 4 months and done about 600 miles on it. The brakes are Shimano BR-M355 with Formula 6 bolt rear hub 135mm QR.

I did try and bed the brakes in by doing a few stops from 15mph. I've checked the rotor and caliper bolts and they all seem tight to me. I cant see any play in the hub either, although I'm not sure the best way to check this. Also I have been careful not to contaminate the pads with any oils.

Should I just try taking the pads out and rubbing them down with some fine sandpaper?

The performance of the brakes are great but the noise on steep sharp descents is very disconcerting so would appreciate any advice.

cooldad

Are they juddering or making a noise?

Chunkers1980

Check the pads are engaging with the centre of the disc fully on the braking area and what cd just said

mtbjunkie08

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19721406#p19721406]cooldad[/url] wrote:

Are they juddering or making a noise?

They make a noise but I cant really describe it, its not a squeal/squeak, it sounds like a juddering noise.

mtbjunkie08

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19721408#p19721408]Chunkers1980[/url] wrote:

Check the pads are engaging with the centre of the disc fully on the braking area and what cd just said

I'm not sure how to check this because I cant see exactly where the pads touch the rotor as the calipers obscure the view.

Chunkers1980

There might be a wear track. Check it is running fully on the actual surface top to bottom

kajjal

Also take the wheel off the bike and make sure it spins smoothly. I had one where the front wheel hub was far too tight, this made it very notchy when the wheel span round. Loosened it off and the strange juddering noise on the front disc brake was gone. Doing the QR up way too tight can have a similar effect.

JGTR

My new XT brakes do this, was told it was normal :?

kajjal

I have XT brakes and they make a scraping noise when pulled on which is normal. If they judder a lot or sound like a gobbling turkey something is not quite right somewhere. Normal causes are poor alignment, pad contamination or something is loose.

BigAl

To re-state Cooldad's question: is it a 'juddering' (i.e. something you 'feel' like in a car with poor wheel balance or tracking) or just a noise?

If just a noise, then could be lots of causes but probably something minor. If a physical juddering then something's wrong

mtbjunkie08

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19721613#p19721613]BigAl[/url] wrote:

To re-state Cooldad's question: is it a 'juddering' (i.e. something you 'feel' like in a car with poor wheel balance or tracking) or just a noise?

If just a noise, then could be lots of causes but probably something minor. If a physical juddering then something's wrong

I understand the question now, I don't think its something I can actually feel, its hard to check visually for signs of juddering while your going down a steep incline without crashing but I would say its just a noise.

mtbjunkie08

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19721475#p19721475]Kajjal[/url] wrote:

Also take the wheel off the bike and make sure it spins smoothly. I had one where the front wheel hub was far too tight, this made it very notchy when the wheel span round. Loosened it off and the strange juddering noise on the front disc brake was gone. Doing the QR up way too tight can have a similar effect.

Had the wheel off and it seems to spin fine to me.

The Rookie

Juddering is often caused by the pads running too far in (towards the axle) or out (away from) and clippping the spider that holds the disc or running outside on the wavy outer edge (assuming your's are wavy), a close visual inspection is the only way to determine this, either looking at where the pad sits on the disc (yes can be hard) or the circular wear marks on the disc.

mtbjunkie08

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19721918#p19721918]The Rookie[/url] wrote:

Juddering is often caused by the pads running too far in (towards the axle) or out (away from) and clippping the spider that holds the disc or running outside on the wavy outer edge (assuming your's are wavy), a close visual inspection is the only way to determine this, either looking at where the pad sits on the disc (yes can be hard) or the circular wear marks on the disc.

I've tried taking some photos of both sides of the rotor, looks to me as if the pads are using the correct parts of the rotor.

swod1

what size is the rear disc 160, maybe you need to switch to a larger disc?

Also the shimano resin pads aren't the best you could try some others organic, Kevlar etc.

mtbjunkie08

Yes it is 160mm, don't really think a bigger rotor would be necessary. Maybe the noise is just normal as others have said but the front doesnt do it at all.

The Rookie

It is running just a little further in than ideal and perhaps could do with spacing 1mm (maybe loosen the adaptor bolts and see if you can gain that there, but I doubt it's causing the issue.

Maybe try a few good hard stops on tarmac.