New Sram Rival brake noise

[Wright640]

I just installed new Sram Rival group. The rear brakes are making an awful noise, more than just squealing. I have Shimano wheels that are less than 1 year old. I cleaned the wheels. Also, replaced the new Sram pads with my previous pads which are less than 6 months old and still in good shape. Nothing seems to help. I noticed the left pad is barely on the rim but is making full contact with the rim. The right pad is perfect. Almost as if the left arm is shorter than the right. Any suggestions?

[xerxes]

Have you tried toeing in the brake pads?

You can get little plastic tools for this, or you can use a strip of card about 50mm long, 10mm wide and 1mm thick, a strip from a cereal box should do.

You can do each brake block individually, place the card between the rear quarter of the brake block and the rim squeeze the lever tight then slacken off the brake bolt and re-tighten. When you've done all four blocks, you should see that the front edge of the block touches the rim first as you apply the brakes.

There's an article here that might help: http://www.jimlangley.net/wrench/brake1.htm

[Wright640]

(06-03-2010, 07:48 AM)xerxes Wrote:  Have you tried toeing in the brake pads?

You can get little plastic tools for this, or you can use a strip of card about 50mm long, 10mm wide and 1mm thick, a strip from a cereal box should do.

You can do each brake block individually, place the card between the rear quarter of the brake block and the rim squeeze the lever tight then slacken off the brake bolt and re-tighten. When you've done all four blocks, you should see that the front edge of the block touches the rim first as you apply the brakes.

There's an article here that might help: http://www.jimlangley.net/wrench/brake1.htm

---

Yes, I didn't mention that in my original post. They are toed in more than you describe so I will try that as well. Thanks.

[xerxes]

You might also check that there's no play in the calipers as this could lead to them vibrating. But even if you do everything you can, you might find that you just have a rim-block-frame combination that just doesn't want to shut up. You may also find that they bed in after a while and sort themselves out. Good luck.

[Wright640]

Thanks. You may be right it does sound and feel more like vibration than scrubbing like on pad and rim. Do you mean play in the anchor bolt and frame connection or the pivot bolt. Any other remedies to the vibration?

[xerxes]

Any play at any point could allow the brake assembly to resonate/vibrate, so try and eliminate it wherever possible. However, it could just be that the combination of your seat stay length, calipers and blocks are prone to resonating.

I have a problem with the rear disc brake on my hard tail MTB, it sends a "buzz" through the frame. I have re-aligned the caliper and it has cured it to some extent, but it still does it on occasion.

[Wright640]

Still no luck. Everything is tight. It is definitely a vibration that resonates up the seat stays. I removed the caliper and reinstalled. The front caliper works no problems.

It is definitely not something I can live with. Any other thoughts? Thanks.

[xerxes]

Have you tried re-facing the brake pads? To be honest, I'm clutching at straws, but it might be worth a go. Remove the brake pads, place a bit of course sandpaper on a flat surface and rub the face of the brake blocks on the sandpaper until you get a flat, even new face.

Even if this does work, you may find that the noise returns once the blocks have developed a new "sheen" from the rims.

[Wright640]

Thanks for all your suggestions. I went to my LBS and they pointed out that the reach on the Rival calibers was too short. The pads were not hitting the rim correctly, which I did notice initially but thought I would get around. The pads were right on the edge of the rim creating the vibration. I put my old caliper back on and it is working perfectly. So I'm left with the old brakes but a great new drive train. So I'm happy, for the most part.

I have to say that this website is pretty awesome; getting advise from half a world away is amazing. Thanks again.

[sdmott]

I'm having a similar issue on my rear brake: FSR Stumpjumper with Juicy 5's. System worked great until I went riding through some nasty sand/silt. It vibrates/resonates/sounds horrible ever since. All components seem to be tight and I've tried replacing the brake pads.

Any ideas how I might fix or at least isolate the problem?

[xerxes]

Have you tried re-seating the caliper?

Disc calipers are sort of self adjusting, loosen the the mounting bolts with the concave and convex washers on them, the ones you can see on the back of the caliper below:



Now spin the wheel and just dab the brake a few times so that the caliper can re-align itself. Then hold the brake lever tight, use a toe strap if you have one to hand, and tighten the caliper bolts. Take the bike for a quick spin and hopefully you will find it has solved the problem.

[sdmott]

Tried to re-align the caliper as you described... a few times... but I notice no difference. Any other ideas?

Thanks

[xerxes]

Quote:Any other ideas?

To be honest, no, my rear disc brake still squeals and buzzes. It has good days and bad days and I I've improved it, but it still does it on occasion.

The front is attached to the relatively heavy and solid suspension fork, which I suppose provides a more solid mount and some damping, whereas the rear is mounted on a light seat stay which can resonate. So to some extent, it may just be an unlucky caliper/frame combination that you will never be able to tune out.

If you search for "noisy disc brake" on Google, you'll see that it's not an uncommon problem and that there are quite a few remedies, which you could try. Let me know if you find one that works.

One I can think of, would be to fix a large mass to to the seat stay, it will almost certainly work, but it's not very practical.