XTR Brake Squeal

[kwkirby01]

I've just had a new XTR front brake fitted onto my new Thorn rigid fork with rear facing brake bosses. The rim is a Mavic EX721 ceramic. The pads fitted to the brake are XTR non-ceramic (I think).

This replaced a suspension fork and disc brake combination.  Fortunately when the bike was built I had the wheel built with a V-brake compatible rim rather than disc specific rim.

The problem is brake squeal - no need for any kind of a bell on this bike, just touch the front brake lever!

Some thoughts I've had:

1) The rims have done several hundred miles on the original disc brake, so there's probably a build up of gunk on the rim. Could this be the cause? Any ideas as to the best way of cleaning a ceramic rim?

2) Research suggests that XTR brake blocks are known for squealing. Should I try an alternative brake block?

Any help gratefully received.

Kevin Kirby

[stutho]

I sympathise brake squeal can be a pain and XTC are known to be loud.

Try in order

• Scrub the rims with denatured alcohol (remove the tyres first)


• Also try Scrubbing with Muc-off - removes some things that alcohol can't!


• Check the mounting / pivot bolts are tight (8NM)


• Increase the toe in


• Put some talcum powder on the rim (I hear this can work but didn’t work for me)


• Try toe out, works for some (revert to toe in if unsuccessful)


• Try the left pad on the right and vice versa  - expect very bad brake performance. (I don’t recommend this set up)


• Place two rubber washers either side of the pad spacers


• Switch to Cool Stop salmon pads - VERY good breaking but may still squeal


• Add a brake booster


• Switch to ceramic specific pad (green)- breaking will not be as good as salmons but is less likely to squeal


• Sell the XTRs on Ebay and get a pair of Avid Ultimate - the best rim brake bar none (allegedly) cost a packet and can still squeal!


• Buy earmuffs!

Personally I run with cool stop salmon on the front (facing backwards) with a brake booster on Mavic 727 ceramic rim using Ultimate callipers. On the rear I use Cool Stop green on 727, again with Avid Ultimate. I believe my braking is a good as I can make it (which was personally very important to me) and doesn’t squeal but did cost an arm and a leg to get right.    

Good luck it can be a long process to get it right.

PS Has anyone got direct experience of both Ultimate and XTR or Arch Rivals? I was very tempted by Arch Rivals (being less than half the price of Ultimate) and have hear some good feed back about them.  Anyway I made MY choice and am very happy with it.

[kwkirby01]

Thans Stutho, I'll give these a try. Out of interest, where does one get denatured alcohol?
Kevin

[stutho]

Denatured alcohol is Methalated spirit. You could also try isopropanol.  Methalated spirit is avaliale in B&Q

[lewisnoble]

Reviving this topic, which has been quiet for a while . . .

My problem is not so much brake squeal, but shudder.  My raven Tour has ceramic rims, and XTR brakes, and even quite moderate braking causes judder / shudder in the forks; quite disconcerting and liable to induce a skid.  My son's £290 Specialised, with cheapo V brakes, brakes better and more securely.

I have just put new pads on (KoolStop green), and it judders worse than ever.  In fairness, I had better let them bed in before I try anything else, but if anyone has got any ideas . . .

I have increased the toe-in, which has helped a little, but the brakes are still unpleasant to use to stop quickly .

Lewis

[stutho]

You have probably checked this already but have a look at the pre-load bolt on you headset.  With the clamp bolts loosened increase the pre-load bolt torque a little and then retighten the headset clamp.  Too much pre-load WILL damage you headset bearings, too little and the brake will shudder just as you described.

I read somewhere that some people are now getting their pads not only to toe in but also to camber in - top of the pad to contact before the bottom.  I haven't tried this myself but you never know!

[lewisnoble]

Thanks, Stutho, I thought I would hear from you and I welcome the advice.  I had wondered about the headset, but am apprehensive at tackling things I do not know much about.  

Back to the garage . . .

Lewis

[john28july]

quote:Originally posted by lewisnoble

Reviving this topic, which has been quiet for a while . . .

My problem is not so much brake squeal, but shudder.  My raven Tour has ceramic rims, and XTR brakes, and even quite moderate braking causes judder / shudder in the forks; quite disconcerting and liable to induce a skid.  My son's £290 Specialised, with cheapo V brakes, brakes better and more securely.

I have just put new pads on (KoolStop green), and it judders worse than ever.  In fairness, I had better let them bed in before I try anything else, but if anyone has got any ideas . . .

I have increased the toe-in, which has helped a little, but the brakes are still unpleasant to use to stop quickly .

Lewis

Hello Lewis,
From past experience I recall that when this type of problem occured, it was when the shoes were toed in too much! Try setting brake pads almost parallel. Also a wipe down of the rims with Methelated spirits (Denatured Alchohol) or similar.
If the problem persists, I would remove and clean the face of all the brake pads and wire brush them to increase friction.
I do think though that the first suggestion is then best one. What happens when toe in is too much, is that you need to pull extra hard to bring pads level with the rim, this causes a vibration.
Good Luck.
John.
www.pbase.com/john28july

[geocycle]

Lewis, I had the same problem when I changed brake blocks.  Previously I had shimano blocks from new which were damaging the rim (see posts elsewhere), so I subconsciously tried to avoid breaking late.  With the new blocks I am became confident to brake more suddenly, but then the juddering was noticeable and as you say could lead to skidding.  I tightened the headset just as stutho recommends and increased the toe in on the blocks.  This seems to have cured it and the braking is very effective. It may be the new blocks have also bedded in a bit.  

BTW does anyone measure the torque on the aheadset or is it just trial and error?

[Swislon]

When I got judder it was because the headset was slightly loose as I hadn't tightened it after I turned the bars out the box. The Thorn manual explains how to do it if you need to know. Check by standing astride the bike, keep the front brake on and rock the front. If there is any play in the headset you should feel it. I tightened mine and now no judder.

[stutho]

I have got preload torque figure at home and will post later (after work).  It is not very much though <3NM?  I think trial and error would be a better bet than using a torque wrench in this instance.

[lewisnoble]

Well, I have checked everything I can possibly find to check, a modest degree of toe in,(2 layers of card behind the rear of the block / pad) made sure that the XTR mounting bolts are secure, and tightened the headset.  I have tightened it more than I would normally do, but the forks / bars still 'flop' from side to side when the kike is lifted and tilted, though not quite as 'floppily' as before . . .

And they still judder something rotten.  Before I do anything else, I will make sure the new blocks are bedded in, which does not take long in Sheffield.

I am beginning to wonder if there is a fault with the ceramic rim??  While cleaning it, as recommended by stutho and john, I think, I noticed a few small chips / splinters off the rim braking surface, which otherwise felt very smooth.  I am surprised at that, after only about 900 miles of 99% careful road riding . . .

But I will post again after I have ridden for a bit.  I am reluctantly prepared to think about Avid brakes, but want to be sure that is where the problem is!!

Stutho, where do you get a torque wrench going down to 3 nm??  

Lewis

[julk]

Lewis,
Try this link for a 1-20 Nm torque wrench
www.hunter-tools.co.uk/product_info.php?cPath=56_223&products_id=494

[stutho]

Right I just looked up the MAX torque for a Aheadset, the required torque is LESS THAN 2.5NM.  

Like I said early I think trial and error is a better bet than a torque wrench for this adjustment.  If you feel that you really need the tool you can get a torque wrenches to well below 2.5NM, what you are looking for is a torque screwdriver.  If you REALLY REALLY need that tool I have a few spare torque screwdriver see the for sale section (they were clogging up the tool box anyway.) I will reserve you one for a week.

I too have much greater problems setting the brakes on a bike with ceramic rims so maybe this is your root cause.

 

[lewisnoble]

Thanks, stutho, torque driver arrived yesterday.

I am now running on Koolstop (green) with ceramic rims.  In the dry, braking is improved and stable, but in the wet, lo and behold, the judder returns - when of course the risk of skidding is higher anyway.

Any more bright ideas out there??

Lewis