Mountain Biking - Disc brake rubbing in front
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06-23-09, 06:45 PM
But barely. It was real bad, Avid warrantied the front caliper unit, LBS installed the new unit, it had zero rub at first, now it has a tiny bit of rub. My LBS says it's pretty standard that disc brakes rub a little. It's really not bad, but the rear brake doesn't rub at all.
It a bit of disc brake rub standard stuff or what boys? I find that hard to accept.
Also I hang the bike up to store it, could this be the hydraulic fluid collecting in the wrong places due to gravity? I found that after it was down off the wall and I had ridden it around my driveway for 10 mins, the brake rub was much less pronounced.
06-23-09, 07:36 PM
I've had the LBS tell me the same thing on my new juicy 7s, so I think that it is true. There is just so little clearence between the pads and rotor it seems logical. Today at the shop someone knocked over a row of bikes, which then came to all land on top of mine. Figures, right? Two broken spokes and an unrepairably bent rotor on the front.
06-23-09, 08:41 PM
It's not logical to me. Bicycles are not supposed to be resistance trainers. And for some reason I get this on the front, not the rear brake. After tooling around my street for 20 mins or so tonight the brake rub was virtually gone. I won't be storing the MTB hanging up anymore.
06-23-09, 09:12 PM
I've heard not to do that with hydraulics - I dunno. I haven't had them long enough to screw that much up.
Odd. I hang my MTB by the front wheel and have never had an issue with the brakes. I'm using Hayes HFX Mags. Is it possible that the weight of the bike is slightly misaligning the front wheel in the fork while hanging? This might result in the dragging and subsequent 'fixing' of the problem after riding for a bit. Your weight would realign things. Try hanging it again, then loosening the skewer prior to riding, making sure the front wheel is seated fully, then retightening the skewer. If it runs right away with no dragging, you've found the issue. It just doesn't make sense for a fully sealed system to do something like that.
06-24-09, 03:10 AM
I took my bike yesterday to the LBS to have the front rotor aligned. The guy adjusted two allen bolts located behind the caliper, and the rotor started clearing the pads by just a tiny bit. My bike has Tektro Mechanicals though, so your mileage may vary.
06-24-09, 03:55 AM
I had Magura hydraulics once. Rubbing was a constant problem. Before riding, I'd often removed the front wheel and forced the pads apart with a shim, seating the pistons deeply into the caliper. They just didn't want to retract fully.
I couldn't handle it anymore and switched to Avid mechs. Inferior stopping, but far less aggravating.
06-24-09, 09:26 AM
Yes, I would say its normal in the sense that if you go to the LBS and spin the wheels on 20 bikes, 19 of them will have some rubbing front or back.
No. I'm with you in that I think its ********. Been screwing around with mine for years. I'm satisfied with it when you can barely hear it, but if you spin your wheel with the bike upside down it still spins forever.
06-24-09, 01:35 PM
I think that some intermittent rubbing is common, but it should be very light. I can just faintly hear the pads rub the rotor when I spin my wheels in the stand.
If you're getting constant rubbing or moderate to heavy rubbing then I'd make sure that your rotor bolts are all torqued the same and I'd lube the caliper pistons. To do that, pull the caliper, pull the pads and then squeeze the lever to slow extend the pistons. Put a few drops of brake fluid on the pistons then press them back into the caliper. Squeeze the lever, put a few more drops, squeeze them home, and then repeat without using more brake fluid. This will break up any crud or corrosion that might impede the movement of the pistons. Once you've exercised the calipers a few time wipe the insides down to remove any excess fluid, reinstall the pads, and reinstall the calipers. See if that helps the rubbing that you're hearing.
06-24-09, 01:41 PM
maybe you have the quick release on your fork too tight. who knows?
06-24-09, 01:44 PM
it's pretty damn normal. a perfect setup with a nice new setup of brakes and a true rotor shouldn't. IME, most rotor rub is either from trail damage to parts or bad setup.
but once things have been ridden a little bit, it's pretty damn common to have a little rub. bolts can slip, pads don't seat perfectly all the time, and rotors can get little imperfections with enough heat or smacking into stuff on trail, even something you think may have not done any harm. doesn't hurt anything to have a little rub, it's just annoying at times. ride on, and just crank the tunes up a bit more.
grab a small crescent wrench, this, (http://sram.com/_media/techdocs/UM_Juicy_Ultimate_7_Carbon.pdf) and get going. or, as mccoomer mentions - you may need a bleed, or the pistons need to be lubed up a bit if they aren't retracting all the way. dot4 or dot5.1 for the juicy stuff.
pssst: page four, step six.
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