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 Post subject: Juddery Disc Brakes
PostPosted: Tue Oct 02, 2012 9:26 am 
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Joined: Tue Oct 19, 2010 9:55 am
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Location: The land of Lea & Perrins
Time to ask the experts :)

My disc brakes (Hayes HFX Mags with aftermarket rotors) judder when I use them.

I've cleaned the rotors properly.
I've cleaned the pads properly.
I've check the rotors for wobble - they're both perfectly straight.

Could it be the spoke tension in the wheels? Both wheels are ever so slightly out of true, and I'm wondering whether the difference in spoke tension would be enough to cause the wobble in the brakes?

Unfortunately, if this is the case then it means a trip to my ever-so-useful* LBS to have the wheels trued properly, as I don't have a spoke key at the moment and even if I did, I don't trust my skills enough (ie. I'm rubbish) to be able to true them properly without causing problems further down the line.

Any help or advice would be appreciated, as always. If there is anyone living near me who could true my wheels up for the price of an Ale or two, then that would be good too ;)






*by "ever-so-useful LBS", I in fact mean "ridiculously over priced bike store where you have to book a bike in about a fortnight in advance to have even the slightest of jobs done" :roll:


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 Post subject:
PostPosted: Tue Oct 02, 2012 9:51 am 
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Juddering may be caused by the pads hooking in to the cooling holes. My original RX set had the same problem.
Filing off the sides of the pads (the leading and trailing edge) at a 45° angle stopped both the judder and the squealing mine were suffering from as well.


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 Post subject:
PostPosted: Tue Oct 02, 2012 10:05 am 
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Raging_Bulls wrote:
Juddering may be caused by the pads hooking in to the cooling holes. My original RX set had the same problem.
Filing off the sides of the pads (the leading and trailing edge) at a 45° angle stopped both the judder and the squealing mine were suffering from as well.


Thanks for the advice. Might give that a go :)


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 Post subject:
PostPosted: Tue Oct 02, 2012 10:11 am 
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Location: Herts UK
which aftermarker rotors are they?

there are many lightweight ones that achieve lightness by having holes in the braking surface instead of metal and it is usually these that cause judder.

For esxample Hope floating rotors are light but do not suffer from this due to the overalpping of the holes.


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 Post subject:
PostPosted: Tue Oct 02, 2012 10:22 am 
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02gf74 wrote:
which aftermarker rotors are they?

there are many lightweight ones that achieve lightness by having holes in the braking surface instead of metal and it is usually these that cause judder.

For esxample Hope floating rotors are light but do not suffer from this due to the overalpping of the holes.


These are the ones. I don't think that it's the rotors which are causing the juddering, as the brakes did it previously with the stock Hayes rotors.

The rotating direction is anti-clockwise as pictured.

Image


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 Post subject:
PostPosted: Tue Oct 02, 2012 10:33 am 
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I had Superstar Flame rotors that looked very similar to those - juddered really badly on the front. Swapped them for the less lightweight ones and the juddering went. YMMV, etc...


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 Post subject:
PostPosted: Tue Oct 02, 2012 10:49 am 
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hmmmm, that sort of scuppers my idea - is it both wheels that judder? the front is more susceptible as braking shows up any slack in the headset as well as any wear in the forks.


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 Post subject:
PostPosted: Tue Oct 02, 2012 10:57 am 
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02gf74 wrote:
hmmmm, that sort of scuppers my idea - is it both wheels that judder? the front is more susceptible as braking shows up any slack in the headset as well as any wear in the forks.


Yep both wheels, although the front is worse than the back. Forks and headset are perfect - the forks only recently came back from a full service so all bushes etc are 100%.

I think the only thing which is really standing out to me is the slight buckle in the wheels - the difference in the spoke tension might be enough for the brakes to be able to 'pull' the wheel (and therefore rotor) over slightly when it runs past the slacker part - although this isn't something which has happened to me before and I'm sure that not all my wheels have been 100% true!

I'm going to get the wheels trued up and I'll file the pads down a little, as Raging_Bulls suggested. Then if that all fails I'll bung the whole lot in the bin and go back to V Brakes ;)


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 Post subject:
PostPosted: Tue Oct 02, 2012 2:14 pm 
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How did you "clean" the pads, and why did you feel the need to do so? Contamination of any sort?

Are they aftermarket pads or genuine Hayes?


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 Post subject:
PostPosted: Tue Oct 02, 2012 3:07 pm 
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It could be the pads I guess if they're slightly loose in the caliper and can move back and forward. The after market rotors could be exaggerating it.

Without sound daft, have you checked the caliper and mount bolts are all tight? I'm sure you will have, but you never know.

How are the pistons? Do they retract properly?


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