Dragging front brakes

[fxrer]

After sitting for two weeks, I went to take my ’80 SG Special for a spin, and I could barely get it out of the garage, as the front brakes were dragging. This was very odd, as they seemed fine when I parked it after the last ride. I jacked the front wheel off the ground, cracked the bleed screws on both calipers, and the brakes were still so tight, I could barely move the wheel. As detailed in the maintenance section of this site, I cleaned the ”spooge hole” (it looked fine to begin with) and refilled with fresh fluid. No difference. Finally, I was able to remove both sets of pads, compress the caliper pistons a little with a C-clamp, and re-install. The wheel spun freely, but after applying the brakes again a few times, the tightness resumed, and the drag was evident again, although not quite as bad.

Any ideas about what else could be causing this drag? The pads have less than 2 k miles, Fluid is fresh, everything looks clean.

fxrer

[fredintoon]

teardown time

I bought an XS11SG last year. It was a bargain but in sorry state, among many other deficiencies the front & rear brakes were locked on solid. Dontcha love those wacky tapered brake pads? I'd never seen the like before so I thought they were screwed and bought new ones and they were tapered too.
What unstuck my front brakes was completely dismantling the calipers and cleaning all the rust and sludge out of there.
The back brake caliper was also seized and additionally the back master cylinder was full of rust.
I lucked out in that all my brake hydraulics existing rubber things worked fine on reassembly. Be prepared to not be that fortunate.
Fred Hill, S'toon.

[nashville_bill]

That's what happened to mine and I fixed it the same way. I guess the pistons were just stuck. A good cleaning and new seals and I haven't had any more trouble.

[prometheus578]

Same prob. Brought one of my XJ650s into work to toy with when there is nothing to do. Bike sat in my garage for 5 years. Front caliper seized, wheel no turny. Whacked it with a rubber mallet a few times to free it so I could push it onto the lift. Pulled the caliper and cleaned the gunk out of it. Works like a champ. (I won't tell you what the carbs looked like!)

[fxrer]

OK- thanks guys! I had hoped to avoid that procedure, as the manual says rebuilding the calipers requires "special tools and experience". But, it's no good like this, so cleaning is in order.

Any tips I should know about?

Thanks for the input.

[John]

To get the pistons out, you can use compressed air, BUT put a block of wood in the caliper in place of the pads, then apply the pressure. You don't want your fingers in there when the piston comes flying out. Another way to remove a stuck piston is with a grease gun. If you can rig up a way to get a good connection to the caliper, then the pressure of a grease gun will do the job. If you can't do that then just take the caliper off the fork tube pull the pads, and use the master cylinder to pump the pistons out. Keep an eye on the fluid level while your doing this so it doesen't run too low and you start sucking air into the master cylinder. Brake clean or rubbing alcohol are good for cleaning the components and hoses with. Go to a NAPA Parts store or equivilent and buy a small hone for the bore in the calipers. That will ensure they don't get out of round when you try to clean up the bore with a piece of sandpaper.

[prometheus578]

I agree with John, but I wouldn't hone. Most people on this site may not be professional mechanics. There is the risk of being too eager and honing away too much material. Yes, honing is the correct way to do them if you know what you're doing. Cleaning calipers is easy, and I would recommend using the master cylinder to push the piston out. Once out, use a dental pick, or modified piece of coathanger and scrape all the gunk out of the groove that the rubber ring sits in. I've seen rings with dry gunk on them... just use your finger nail and some brake fluid to clean it. (some say don't use brakeclean or other solvents, as the rubber ring could swell.) Take a small piece of 600 grit or finer sandpaper and just swirl it around the inside of the caliper a few times till it's smooth. Do the same with the sides of the piston. Put the piston back in the caliper(Dry, without the rubber ring in place) The piston should move in and out freely, but be snug, as there is a close tolerance between the piston and the walls. Remember that the piston's concave face goes in, and the hollow, rusty section faces out toward the brake pad. Pull the piston out, put in the rubber ring, lube everything with brake fluid, and work the piston back into the caliper. Assemble, and bleed the system.
Easy job, Fxrer

[TopCatGr58]

Hey there Fxrer,

The outer edge of the caliper has a thin rubber dust cover, held in place with a large "C' type ring, it can tear the dust cover if you're not careful pulling it off before pulling the dust cover off. Surprisingly, the rubber O-ring is pretty strong, and I was able to go back with my old one after it sat for 9 years!!!! You may find some pitting on the inside concave surface of the piston, where it is next to the caliper and fluid chamber, but the rubber O-ring is what makes the seal, so just buff any pits you find and put it right back in! The aluminum caliper body doesn't rust so honing isn't really needed, just gets gunked up and you might find some mild corrosion if there was any water in the brake fluid, I used find emery cloth vs. sandpaper! Just take you time and be cautious, and you'll succeed!
T.C.

PS, I just editted it, but who really cares about spelling!?

[prometheus578]

I wrote sandpaper instead of emery cloth 'cause I couldn't 'member if it was spelled with one "E" or two.