Howling Rear Juicy 7's

[Bryguy17]

for changing rotor size, it doesn't really matter. either way will change the frequency that the brake system vibrates at (higher for smaller rotor, lower for larger rotor, but that doesn't matter). Shouldn't matter what type of rotor either. I'd say find a friend with a spare rotor/adapter you can borrow to try it out.

[92se-r]

LOL, that is the best way to describe the Avid brake noise. Every single set of Avids I have or have experience with, makes this same "gobble". HAHAHA. My Hayes on the other hand are dead silent unless you get them really REALLY REALLY hot.

Originally Posted by Zippy

If you mean the Turkey "gobble" then it's just normal for the rotor and many people I've talked to have that problem, me included. If it's a loud squeal, I fix it by the steps you've already mentioned. Maybe turn your headphones up?

[OldDogDan]

Occasionally something as simple as increasing the tension on your QR can stop it (the resonance thing..).

[mottmcfly]

Originally Posted by TDUB

Ok im going to look into getting the mounts refaced. As for changing rotor size should I go down or up in size? And should i stay with the avid rotor or should i try another brand? I currently have 185mm on the rear.

I have a similar problem with my Hayes Stroker rear 8" brake on a Mavvic wheel. Hayes told me that the problem was due to the "acoustics" of the wheelset. Funny this doesn't occur on the front. The poor bike shop has tried just about everything including glazing the pads with a torch. I am thinking about reducing the rotor to a 6" just to entertain the acoustic theory.

[Bryguy17]

the acoustics of the front wheel will be different from the rear wheel though, so you're likely only going to experience the problem on one or the other. DIfferences in spoke length, tension, hub spacing, qr tightness, acoustics of the fork/frame will all effect whether or not it resonates. it really is amazing that it happens so often, considering all of those factors must be perfect for that to happen.

One known example of it happening is on older trek fuels using formula OROs. they would just resonate and make the whole frame shake violently.

bad stuff, but at least its not as bad as this:
http://youtube.com/watch?v=a4EvVR10AF0

[dstepper]

I have often thought if using caliper and rotor washers, bolts and spacers maybe out of a anti-vibration material like nylon would be the cure...maybe anti vibration mounts.

Dean

[Bryguy17]

Originally Posted by dstepper

I have often thought if using caliper and rotor washers, bolts and spacers maybe out of a anti-vibration material like nylon would be the cure...maybe anti vibration mounts.

Dean

the only problem with this is flex. We have a hard enough time keeping rotors/calipers adjusted into the right place. If you used a vibration dampening material, you would end up with potential play in the system, which just leads to more rubbing rotors, calipers moving under hard braking etc. The vibration would just end up being transmitted through the bolt anyway. for something like brakes you want solid mounting, which just doesn't work for vibration dampening.

[TDUB]

The two things I am going to try are:

• Get brake tabes faced.
• Change rotor size.

Im going to do each change individually. That way I know what actually works, if they work. The other options I am considering is a new wheel. If it is afrequency issue that changing to a different wheel might work also. That is going to be my next option.

Thanks for all the ideas! It might take me a while to actually get to test these cause i dont know when my knee is going to be better. Ill keep this thread updated.

[DeeZee]

Originally Posted by TDUB

The two things I am going to try are:

• Get brake tabes faced.
• Change rotor size.

Im going to do each change individually. That way I know what actually works, if they work. The other options I am considering is a new wheel. If it is afrequency issue that changing to a different wheel might work also. That is going to be my next option.

Thanks for all the ideas! It might take me a while to actually get to test these cause i dont know when my knee is going to be better. Ill keep this thread updated.

Do that first


"The other options I am considering is a new wheel."

How about getting different brakes

[TDUB]

Other than the howling im really happy witht the way the Juicy 7's perform and the rear is brand spanking new.

Plus I have been wanting to buy a real nice/light wheelset. So it just becomes an excuse to buy new wheels!

[Bryguy17]

instead of buying, you could also have someone who's good with wheels (or yourself) change the total tension of the wheel. a slight increase or decrease in tension will change the resonant frequency of the wheel, possibly alleviating the problem.