couple xj brake questions

[nightpilot]

I have been rebuilding my brakes. although I had gone through all of them the back brake stuck on and the front was a little tight. when i took them off the pistons were stuck. this is after i had gone through them, cleaned inside the channel the oring and everything. I cleaned them again very carelfully and still they do not seem to be very free. Used lots of brake fluid to put them together. They went together pretty tight and when some air pressure was applied they were stuck a little and came free as if breaking
free.

Oh also cleaned out the master cylinder spooge hole and all and lines.

Question 1 how tight should the piston be, should they not move smoothly rather than feeling like they are sticking?

The orings look perfect, could it be that they got hard with age and a little more tight - the cause of the sticking?

I wonder if newer softer orings would cure the problem. I saw they were available, is mikes the source?

Question 2 on the front calipers the shaft goes through the hole in the top of the brake pads and holds them against the spring. I had to really push hard to get the pad hole high enough to put the rod through and the pads seem very tight against the spring. I cant imagine they would move very easily. Should the pads be that tight against the spring? Should I grind the tops of the pads down to make less pressure?

thanks guys.

[CatatonicBug]

The pistons should move fairly freely when cleaned. You should be able to press them IN with a pair of channel locks without any trouble, and without any resistance or snagging.

If it were me, I would replace the rubber seals. I get the front ones from here. This is the one for the rear. The calipers on the XJ are the same as the LH.

You said you cleaned out the groove for the seal. Did you get BOTH grooves? The fronts have 2 seals. The outer is a dust seal, but still can cause the problem you're having. The inner is the main pressure seal. Both seals need to be removed and cleaned.

The pads should not need to be pressed in to get the pin through them. Are you sure the spring is in the right way? There is a notch cut out of one side that kinda sits over a small bump on the caliper. It can easily go in the opposite direction. A picture might help...

[crazy steve]

...Question 1 how tight should the piston be, should they not move smoothly rather than feeling like they are sticking?

The orings look perfect, could it be that they got hard with age and a little more tight - the cause of the sticking?

I wonder if newer softer orings would cure the problem. I saw they were available, is mikes the source?

Cleaning the grooves is a very important part of a rebuild, but did you clean the bores also? I'll always test-fit the pistons without the seals to make sure I have free movement. With no seals, these should drop into the bores easily when held straight. After assembly, you should be able to push the pistons in by hand if everything is good. Excessive pitting or out-of-round pistons (if they've been dropped on a hard surface) will cause problems, and in either case the pistons will need to be replaced.

New seals won't hurt, but for your special front brakes you'll need to go with PartNMore.

'78E original owner

[CatatonicBug]

New seals won't hurt, but for your special front brakes you'll need to go with PartNMore.

Huh?? Are you referring to the pads, or the seals? For the fronts, the XJ (and LH) uses the flat pads, just like the rears on all the other XS11's. I get them from here. The rears are just like the front right pads on the specials, and I get them here. PartsNMore is another potential vendor, but not the only one.

[nightpilot]

Actually, I did not have dust seals for the front so wasnt messing with them, I am going to get new seals and hope that does it.

for the front pads, I know of the notch cut out for the pin and it was right but i had to push the pads hard against the spring to get them in, I think I probably should grind off the top of the pads so they arent so tight against the spring. I wonder about grinding off antifriction coating on top of pad.

I checked the piston and goes in very easily with out seal. I could push the piston in with the seal in by a piece of wood in middle without much trouble but still when put a little air in to move it out it still wanted to be stuck before it moved.


thanks for info and sources, my mechanic pushed them in for me in the past and went in kind of hard but they have been hanging up and thought that might be the cause.

[CatatonicBug]

Actually, I did not have dust seals for the front so wasnt messing with them

Do you mean the outer groove was empty?? There are 2 grooves in the caliper bore that each hold a seal. The outermost groove is a dust seal. No external dust seal on the fronts - only the rear one has that. Just make sure you clean under BOTH o-rings in each caliper.

[crazy steve]

....PartsNMore is another potential vendor, but not the only one.

He referred to MikesXS, who doesn't carry any brake parts that fit anything other than 'standard' 11 front brakes and some of the earlier rear parts; I just pointed him in the direction of somebody who actually has the parts that fit his bike...

'78E original owner

[nightpilot]

yes the outer groove on the fronts just had goo in them and mechanic said to just clean them out as they might make it stick and that I could get away with not putting anything in them for the time being.