Front disc dragging.

Message

bmlawless · Fri Nov 04, 2005 11:11 am

My front brake (single disk hydraulic) was a bit mushy, so I bled it. It was still squishy, so I pulled the caliper and noticed that the piston was having a lot of trouble moving. I removed the caliper, disassembled everything, cleaned it, put everything back together, and flushed and bled the system. The brakes are much better, but I determined that I still need a new piston and seals as well as pads (probably upgrade to stainless lines while I'm at it).

The problem is that my front brakes drag now. Before I started, I could kick the front wheel and get a couple of rotations. Now, although it is still easy to move the wheel, it does not spin freely. There is no effect when riding and the rotor does not heat up.

I think this is OK, and the new piston and seals will remedy the problem, but I wanted to run it by the folks here to see what you all thought.

mydlyfkryzis · Fri Nov 04, 2005 12:29 pm

The pad is supposed to drag lightly. That keeps wiping it clean and if you are in the rain, keeps wiping the water off.

If the caliper and pad are not overheating, then it sounds right. There is a check valve in the master cyclinder that keeps a little pressure on it for this reason.

Mottoxfox · #3 Unread post by **Mottoxfox** » Fri Nov 04, 2005 9:39 pm

Take back apart the front caliper. The square Oring needs to come out to be cleaned. Scrape the recess groove for the oring until clean. Then I use a single edge razor blade and gently scrape all 4 sides of the oring. Lots of times old crusty brake fluid gets behind the oring pushing it out against the piston causing it to seize up.

Tarheel365 · Mon Nov 07, 2005 3:07 am

my brakes drag lightly as well and don't heat up. it should be fine.
if ur taking the calipers apart u may as well check the piston body for any scores are markings in case that is causing it to get stuck.

but i think what u have is ok.

bmlawless · #5 Unread post by **bmlawless** » Mon Nov 07, 2005 8:10 am

Thanks for the replies. The piston has some marks on it and the square o-ring is really chewed up which is why I say that I still need to replace a few parts. I just have to set aside time for it.

shoey949 · #6 Unread post by **shoey949** » Thu Nov 24, 2005 5:38 am

how do you remove the piston from the caliper as mine are sticking a lot as well?

Thu Nov 24, 2005 12:42 pm

you can get the caliper pistons out by removing the pads and pumping the brake lever.it is best to put a piece of wood between the pistons so they dont come all the way out.sometimes one of them wont move and the other comes all the way out leaving no way to move stuck piston.when they are almost all the way out put a rag around the piston and pull it out with a pair of pliers.if you have a air compressor you can blow them out.you can hook a grease gun to the bleeder screw and push them out with grease.this makes a big mess.hardware stores carry an internal pipe wrench that you can split the caliper and pull them out with the wrench if you have hollow pistons.dont scar the outside of them pistons with pliers or you will get to buy a nice shiny set of new ones.

Mottoxfox · #8 Unread post by **Mottoxfox** » Thu Nov 24, 2005 8:36 pm

Place a thin piece of wood on the opposite side of the piston. Blow compressed air in through the banjo bolt hole making sure the nipple bleed screw is closed. It will pop right out.

shoey949 · #9 Unread post by **shoey949** » Sun Nov 27, 2005 10:47 am

alright now that I have the pistons out what am I focusing on to clean?

BuzZz · #10 Unread post by **BuzZz** » Sun Nov 27, 2005 10:55 am

shoey949 wrote:alright now that I have the pistons out what am I focusing on to clean?

Anything that moves against anything else. That would be the caliper pistons and the piston bores in the caliper itself. And check/replace the seal in there too......