Disc brake help

[gomez308]

I just bought a used Karate Monkey with Clim8 hyd disc brakes. I can't get the rub out. The front isn't too bad, but the back really drags. I've never used disc brakes before and I can't find any info online about these brakes. Any advice would be greatly appreciated.

[xjahx]

Gomez, a small amount of rub is almost always inevitable on disc brakes, but the expected amount should not greatly affect the ability of the wheel to spin freely.

There are two cuplrits:
1. Out of true rotors (either from damage or from warping under the heat of braking). To true a rotor, you can look for high or low spots and then use a tool such as these to bring it back to position. This can be done with the wheel mounted with the rubbing on the pads as a reference for high/low spots or on a truing stand with a guage (made by Park):

http://www.utahmountainbiking.com/shopmiva/images/Morningstar%20Tools/drumstix.jpg

The 3 tool based truing is preferred over the 1 tool based truing because it allows you to focus your force.

2. Pads need to be reset: To do this, you remove caliper from the mount and use a large, flat bladded screw driver (or Park specific tool) and press both pistons back into the caliper. Then, with the caliper and the wheel mounted, you spin the wheel as you begin to pull the lever. The calipers should be self centering (I do not know what this specific mount looks like), but you can also adjust caliper position with shims (washers) between the frame and the caliper.

I hope that this helps.

[gdw]

The Clarks website has videos.
http://www.clarkscyclesystems.com/instruction_videos.php

[Russity]

I don't know anything about the brakes themselves, but there are a few things you can try to remove the rub:

Make sure the rotors are true, with no buckles or dinks in them. Spin them and look for any movement at all (just like a buckled wheel). If there is movement, give it up right there and get a new rotor. Also make sure the pads are mounted correctly. I know this is an obvious one, but we sometimes overlook the obvious.

Take the pads out and push the calipers all the way in to their minimum. Place the pads back in and squeeze the lever to see if the pads re-align themselves against the rotor. Some brake systems also have adjusters on the caliper mounts for small amounts of adjustment to aligning. If you can be bothered and are technically proficient it might be worth bleeding the brakes while you have the pads out. It cant hurt to try.

Your LBS should have a bunch of brake shims. These are very thin little inserts that you can place between the caliper and the frame/fork mount on either of the bolt mounts. Using one at a time, you can insert them and then tighten the caliper bolt. The shim acts as a washer and pushes the caliper in the direction of the shim to ease it away from the rotor, hopefully removing the rub. This is quite time consuming to get right, because you may have to try inserting shims in both mounts to see which way the caliper needs to be pulled, but it usually works if all else fails.

Good luck.

[Marcusaurelius]

If the rotor is slightly off it can cause rub. There's a tool availabe to adjust the rotor.

[gomez308]

Rotor was straight.

Pots were in all the way.

Caliper needed to move a bit closer towards the mount, but there is no lateral adjustment on these brakes. I ended up filing off just a skoosh from the mount to allow the caliper to move over. So far so good.

Thanks for the help.