Dean Hardtail Disc Noise

[navigator]

Anyone had a problem with rear disc vibration noise? Any ideas?
I have a 2005 Dean Colonel Ti hardtail with the aluminum modular dropouts/brake mounts,I'm running Magura Marta disc brakes. I've had the frame and brakes about a week now and am getting fustrated by a LOUD vibration from the rear brake when stopping at lower speeds (like going downhill into a tight switchback). I've tightened everything, the mounting bolts, skewer, hub bearings etc. I've tried a different set of pads. MY LBS has confirmed that the alignment and set up on the brakes is good, they suggested it might be the way the modular dropouts have the disc caliper mounts cantilevered out, not attached to the frame (see attached picture in link below). I called Dean and they said they have not had any history of problems with this set up.
http://www.more-mtb.org/forum/attachment.php?attachmentid=1806&stc=1

Does anyone have any suggestions?

[jabberwocky]

Warped rotor? The front rotor on my Turner is bent up (result of multiple crashes), and it certainly warbles at low speed. If you can, put the wheel in a truing stand and attach a zip tie to the stand leg and use it to check the rotor. You can gently bend them with a crescent wrench and get them pretty straight.

[navigator]

No, the rotor checks out fine, it's not warped. I actually tried a Hayes rotor I had on hand as well just to see if something about the Magura rotor might be the problem but the noise didn't change. Good thought though, thanks.

[BikerMiker]

Whoa. Thems some dropouts...

Sometimes sh*t just makes noise. Stop using those brakes, they just slow you down...

mike

[g_barr]

I've got Marta calipers and SL levers. I finally have the perfect word to describe what I hear after riding tough trails, twisty track and braking slowly/hard (thanks jabberwocky!). My rotors are wearing but straight, pads are fine, oil is fine...

Another noise I get transmits through my XT hubs - it sounds more like a vibration/groan. After four years, it hasn't gone away. You haven't given us any juicy details though:

You've had the bike and brakes for a week - are these your first disk brakes ever?
Are these your first hydraulic brakes?
What kind of hubs, spokes, wheels are you running? Are they the same on the front and back? Does the front make noise? What kind of fork mount do you have?
Are the pads wearing evenly?
Did you buy the bike used, brakes new?
Are you using genuine Magura pads?
Noise when? Wet, dry, dusty...?

[navigator]

Vibration/groan sounds right on the money, As for juicy details:

This bike is a new build for me while most of the parts came off my old frame I got the frame (used ), brakes (new) and wheelset (used, Mavic Crossmax SLR) on eBay. My old Ti frame had V brakes but I do have some Hayes 9 hydraulic discs on a Trek Fuel 80 I seldom ride (for sale by the way), the Hayes made some noise when new, but that went away pretty fast. I'd say I have probably about 15 hours on the new Dean and this groan is much worse than anything I got from the Hayes.

The brake pads are genuine Magura, I actually replaced the pads that came mounted in the caliper with an extra pair of Magura Performance pads that were part of the auction (thinking maybe the pads had gotten crapped up somehow) . The front fork is a Rock Shox Sid (IS tabs)with matching Maguras, no problems there. The pads are wearing evenly, both right side/left side and top to bottom.

The vibration is worst at low speeds going downhill, braking hard, cleaning the rotors with alcohol seems to stop the problem for about 4 or 5 stops, as does wetting the pads with water. I've noticed the noise both on the trail (which these days has been quite dusty until the rain came yesterday) and on the pavement, the new switchbacks at Wakefield are a good example of the worst case scenario.

I have seen some improvement by tightening up EVERYTHING around the rear mounts; IS mounting bolts, hub bearings, skewers, disc screws, and especially the crank bolt style bolts that hold the aluminum dropouts to the frame. I'd say this has decreased the threshhold where the problem appears about 50%. In otherwords it's just as bad half as often.

I've ordered some Kool Stop and Galfer "organic" pads to see if they make any difference. It's been suggested that my problem might be similar to what seems to be commonly refered to as the "Avid Turkey Gobble" which someone mentioned organic pads solved for them. Who knows maybe organic pads will help stop global warming too :D

Thanks again to all who have taken the time to help with this I REALLY apreciate it!

[g_barr]

Our set-ups are real close. The front warbles but doesn't vibrate/groan. The rear vibrates/groans in the same situation as you describe - dry, slow, braking hard downhill. I'm not a physicist, but I think the sound originates at the 'pinch point' and is transmitted/attenuated through the rotor, hub and spokes. I think the pressure hydraulic pistons put on the rotor increases the effect since I've only heard mechanicals squeal.

My new pads (genuine Magura, two sets in four years) squeak and squeal until they fit the rotors. They squeal after cleaning (usually just water) and when wet but that's expected too. Your description and my experience with the Martas makes me believe the sounds you are hearing are normal - especially considering Dean reports a clean history.

My Marta levers did leak - front in the first year; rear in the second year. But Magura replaced both with Marta SL levers no questions asked. I've been very pleased with their performance and wouldn't consider buying anything else.

[CountZero]

Let's say you've been running a set of pads for 6 months, then for whatever reason you realign the caliper.

During that 6 months, your pads had worn in to the plane in which they contacted the brake rotor.

Now, you've realigned the caliper, and thus changed the plane in which the pads contact the rotor.

And thus results vibration.

Really, there are many, many causes for vibration in disc brake systems. Even a hair of axial misalignment results in a vibe.

If it's really severe, a floating rotor like Hope makes might help a bit.

I say just live with it.

[navigator]

I'm afraid my Type A personality is going to be very resistant to living with this. I get what CountZero says about the pads needing to wear in and I keep wondering if maybe I'm just being impatient and just need to let things settle in. On the other hand it sounds like G_Barr's been dealing with this quite a while. I can't help but beleive this can be fixed, or improved to a level I can put up with.

I'm still trying to seperate out all the variables, I swapped out the entire rear wheel/disc with the wheel and disc from my Trek and still had the problem(!!). On a whim I swapped the front and rear pads (after putting the Mavics back on), with a couple dozen stops it is, so far, MUCH BETTER!! I decided to quit for the evening while I'm ahead. I'm crossing my fingers but not holding my breath...

If I need to, I think this weekend I'll swap out the whole rear brake system for the Hayes from the Trek. That will leave the frame as the only variable that hasn't been eliminated.

[navigator]

Success! After checking EVERY imaginable set-up parameter and following up on all the great advice offered by everyone here, I finally found the solution in simply changing to aftermarket brake pads. I know Magura has thus voided all my warranties, but installing Kool-Stop pads has been nothing short of a miracle! The vibration is gone and the brake feel is much more progressive, less "on/off" than I was getting with the stock pads. Again and always, thanks so much to all who took the time to help me sort through this.

Ride On!