Front brakes binding / rubbing

[adi1974]

Hi guys, just bled my front brakes (dual disks on a 78 special) after reassembling my wheels. Its been off the road for a couple of years.

The brakes seem to work fine except that they're dragging a little. Taking my rear brake as an example, I can spin the wheel (totally free of drag) brake and then the pads release and the wheel spins freely without any drag at all. My front however doesnt have as much freewheeling and there is a constant drag after releasing the brake. Its not really bad, its not difficult to turn the wheel or anything but if you spin it and release it comes to an immediate stop unlike the rear which will spin.

Whats the drill? Could it just be a small layer of corrosion on the outside of the piston? Would a bit of freeing up / greasing the lip of the piston help do you think? Gonna look at again in the morning so if anyone has any advice to give that'd be a real help to get me off to a good start on the morrow.

Cheers all.
Adi

 

[Dennis]

yea sounds like so corrosion on the piston

 

[kvanderploeg]

If you're going to replace the piston(s), there are aftermarket stainless steel pistons available. I just used them to rebuild my calipers. Found mine on eBay.

Kent

 

[Belle]

Might need to adjust the pads--been a long time since I worried about disc brakes but most models allowed for brake pad adjustment. Could be a warped disc too.

 

[adi1974]

Pretty sure its not warped disks. They look good when I spin em and its a very consistent feel to it. If its corrosion on the pistons can I try some sort of cure or am I looking at new ones / overhaul? Pad adjustment? Cant find any info on that. Cheers for the help

 

[gggGary]

Straight up? Do a full tear down and clean up of the system. If it's a bike you are going to ride that's the only answer. It could be just gunk built up under the piston wipers, it could be rusted pistons, it could be a plugged port in the master cylinder it could be a hose disintegrating and chunks of rubber have plugged it up. It could be your life on the line. Some times it's minor other times you shake your head and say damn this could have killed me at the next stop. There are very good full brake overhaul threads in the tech section.

There is no "pad adjustment" on an XS650.
Living in the north I almost always find some rust on the pistons if the pits are small I use very fine paper smooth the edges and put em back in never had a leaker yet but if the rust is bad you need new pistons.

 

[Detale]

If its just a little corrosion you could possibly sand it off but honestly it's your brakes, arguably the most important feature on a motorcycle so you should probably replace them.

EDIT: gary put it better and beat me by 20sec.

 

[gggGary]

And detale said sand the pistons if the rust isn't bad first, LOL VERY fine paper 600 grit or finer.

 

[adi1974]

fair enough guys. At the moment I'm no where near road ready so when I am I'll start to look at giving them an overhaul. Cheers for the advice

 

[gggGary]

True tales of the old bike fixer.
CB1100F new to me got r running did a 10 mile shake down cruise. It started "losing power" but seemed like it was running good??????? Finally it came to a halt, rear brake was smoking hot and on full. Plugged port in the master cylinder prevented the pistons from retracting. If it had been the front brake it might have been real ugly.

 

[adi1974]

Warning heeded. Thanks. Just so I know. Should the pistons squeeze when the brake is pulled then retreat somewhat?

 

[gggGary]

Yes a smidge of retraction is normal. You can usually see the whole caliper flex and move a bit as you apply and release the lever.