Rubbing disks!

Chard

Chard

New Member
My disks rub ever so slightly against the brake pads, both front and rear. You can hear it, not constant, just a certain spot or two as it rotates.

No visual warping, but maybe they're slightly warped? [Also describes my mental state!]
I tried to reposition wheels in their dropouts to make sure wheel is sitting straight. Didn't help.

Gary Fisher Cake 2 (2006), I think they're hydraulic? I bought it used so don't know the maintenance previous owner did.

Is there a way to back off that distance between brake pad and disk? My brakes are pretty tight (short lever travel needed to stop).

Thanks for any help!
Rich
 
You can true the rotors with a tool like this:

parsldt2.jpg


http://www.parktool.com/products/detail.asp?cat=14&item=DT-2
 
You should be able to tell by looking down at the caliper and seeing if there is any length of brake cable sticking out, like this Avid BB(7?) Hydraulic brakes will not have that cable

avid_disc7.jpg


Perhaps one of the real shop guys can chime in and add something more but I had the same problems with my Hydros.

I found a solution on some forum that said stick a business card on either side of the rotor and run it through the caliper a few times. It worked for me wonderfully.
 
Last edited:
Yes, then I'm definitely hydraulic! At least I know that now.

Good idea on the card inserting, as I think they self-adjust based on when they make contact with the pads, or a card.

I'll look into that tool also.

Thanks Droptop and Deezul!
 
This can help or make it worse..

Sometimes rubbing can be cause by sticky pistons. When the pistons get dirt and brake dust caked up they can drag. This can also happen when you have air in the lines, dirty or low fluid levels.

To animate the pistons you need to remove the pads and pump the lever a bunch of times. THIS CAN MAKE A BIG MESS IF YOU F IT UP!!!

While holding one piston in with some sort of tool you can extend the other piston. Do this a few times and switch sides. You should find that this lubricates the pistons and allows them both to extend and retract smoothly at the same rate.

**If you push the pistons out too far you will have fluid all over the place.**

Basically this is a trial and error situation. I have overextended every type of piston and in every case you will end up covered in oil. If this idea scares you you should not try this.
 
jdog said:
Sometimes rubbing can be cause by sticky pistons. When the pistons get dirt and brake dust caked up they can drag. This can also happen when you have air in the lines, dirty or low fluid levels.

To animate the pistons you need to remove the pads and pump the lever a bunch of times. THIS CAN MAKE A BIG MESS IF YOU F IT UP!!!

While holding one piston in with some sort of tool you can extend the other piston. Do this a few times and switch sides. You should find that this lubricates the pistons and allows them both to extend and retract smoothly at the same rate.

**If you push the pistons out too far you will have fluid all over the place.**

Basically this is a trial and error situation. I have overextended every type of piston and in every case you will end up covered in oil. If this idea scares you you should not try this.
Click to expand...

Thanks jdog, I'll try this as a last resort.
Rich
 
I inserted thin cardstock between pad and rotor, pumped the brake, then removed the pad, and eliminated rubbing on the front. The card idea worked!

The rear rotor seems to be slightly warped. A thin card would not fit in there, so I took a small amount of material off of both pads with a Dremel tool.
Now it just misses rubbing, so that worked!

Can a slightly bent rotor be straightened/trued like a rim, with that Park tool? Mine wobbles by about 2mm.

Thanks for all the helpful input!
Rich
 
Chard said:
Can a slightly bent rotor be straightened/trued like a rim, with that Park tool? Mine wobbles by about 2mm.
Click to expand...

Absolutely. In fact, some rotors can be trued by hand w/o tools, or you can also use a cresent wrench (the smaller the better!).

You will need to ID the center-point (of the out-of-trueness) along the rotor's outer diameter. Rotate the rotor 180 degrees away from the caliper and flex it in a correcting direction. Re-check with a pass through the caliper and repeat as necessary. Be careful not to overdue it with your "corrections" - several slight corrections are better than one big one...

I would true the rotor rather than remove material from the pads.

Tom P.
 
one piece crank said:
Absolutely. In fact, some rotors can be trued by hand w/o tools, or you can also use a cresent wrench (the smaller the better!).

You will need to ID the center-point (of the out-of-trueness) along the rotor's outer diameter. Rotate the rotor 180 degrees away from the caliper and flex it in a correcting direction. Re-check with a pass through the caliper and repeat as necessary. Be careful not to overdue it with your "corrections" - several slight corrections are better than one big one...

I would true the rotor rather than remove material from the pads.

Tom P.
Click to expand...

Sounds good! I agree, definitely better than removing material from my brake pads.
I will try this and hopefully not to make a mess of it!
Rich
 
Rich

Have you tried centering the caliper on the rotor

You loosen the caliper mounting bolts squeeze the brake lever

and tighten the bolts while continuing to squeeze the lever

That may give you enough room to deal with a slightly warped rotor

or maybe your problem is a slightly out of alignment caliper

I would try this before messing with the disc

Mick
 
Last edited:
I have found that most hub axle nuts are not perfectly square. If the brakes drag, undo the QR, spin the axle 1/2 turn and try again. The clearnce can also be affected by the tightness of the QR.
 
Mick, I tried that, good point though. I noticed how its position can shift when the mtg. screws are loosened.
Thanks.

Trailhead, I'll try that.

Thanks again, guys!
Rich
 
You must log in or register to reply here.
Back
Top Bottom