New brake pads installed, wheel locks?

[Olof.he]

I bought new brake pads at wemoto(called GG type, made for the XBR), but after trying to mount them, the wheel locks up!

Its not THAT advanced?
You take off the caliper, you remove the retainer plate, and then the retainer pins, then you push in the pistons as far as you can. After that I just installed the new pads, and reinserted the pins and retainer plate and screwed it back on... even before I touched the brake handle the wheel is locked up. Why is this? I opened up to make sure that there was enough space for the fluid to flow when pusing in the pistons.

The side where the pistons are is where the pads grips the plate.

Still, it just locks up! Why?

[bullet350]

 are the pads just hard against the disc on one side, or both?

bullet350

[SteveC#222]

Just a few thoughts.

1/ Did you push the pistons right in? They should go in almost flush to the caliper body and it can take a bit of doing. Were the pistons free from pits and corrosion?

2/ Is the brake pad 'hanging up' on the pins?

3/ Is the brake reservoir overfull? If your old pads were well worn chances are you may have added extra brake fluid as the pads wore down. Now you have new full thickness pads you may now have too much fluid in the reservoir for the vacuum to fully pull the pistons back. ( this happened to me!)

Wemoto parts are usually very good.

As you've changed the pads it's worth replacing the brake fluid while you're at it.

Sorry if I'm stating the obvious here.  If you go to www.xbr.de there is an article on rebuilding the XBR caliper.

[Olof.he]

Just a few thoughts.

1/ Did you push the pistons right in? They should go in almost flush to the caliper body and it can take a bit of doing. Were the pistons free from pits and corrosion?

2/ Is the brake pad 'hanging up' on the pins?

3/ Is the brake reservoir overfull? If your old pads were well worn chances are you may have added extra brake fluid as the pads wore down. Now you have new full thickness pads you may now have too much fluid in the reservoir for the vacuum to fully pull the pistons back. ( this happened to me!)

Wemoto parts are usually very good.

As you've changed the pads it's worth replacing the brake fluid while you're at it.

Sorry if I'm stating the obvious here.  If you go to www.xbr.de there is an article on rebuilding the XBR caliper.

Hello again!

I've removed some fluid, so its not that.
The pad is locking on ONE side only, even tho I have'nt started to push out the pistons with the brake handle yet. It is locking on the non-piston side.
Are you sure the pistons are supposed to go flush with the caliper body? Me and a friend tried and tried and tried to get it all the way in, but theres still a bit left still, but there's no more force left in me without either broken thumbs and fingers or extreme violence with a screw driver.

[CHRIS211083]

hi, they should go flush with the body. what you need to do is eject both pistons and clean. then you need to clean the dust seals as this is were the crap get to. then re-asemble the caliper. as for it not loosening off, the sliding pins need lubricating and need checking to see if they are bent. If so replace. finaly its good practice to change the brake fluid at every pad change as the fluid collects water and becomes less and less good at its job. That and you should change it every two years anyway. In my eyes as a bike machanic for 10 yearsthe brake fuid costs £5 a bottle and you prob wont need the whole bottle? Sounds like sence to me? Also the other thing that could be stopping you is if the caliper seals are swollen then the pistons wont go all the way in and the only thing to do is replace as it with increase pad wear dramaticly!hope this helps, Chris.

[Mark]

Removing and cleaning the pistons is the way to go, and new seals, or if you're like me push them back flush with a 'G' clamp and see how they work.

[Olof.he]

The G-clamp idea seems pretty tempting... ´
But still, one might learn something from having a go at really fixing it.
How advanced is the job to open and clean seal+pistons? I assumes this includes emptying the system from brake fluid?

And where does one get new seals?

Thanks a bunch for help!

[bullet350]

its quite simple as the pistons are only a push fit into the caliper. its also worth checking the pins that the whole caliper slides along, these often end up covered in rust and start to bind.
the hardest part of the rebuild is getting the pistons and the seals back in, but this only takes time and patience.

 bullet350

[guest27]

The pistons are a close fit in the bores - some do not have seals - so they need to be square to slide in.  a easy rocking will find the place and then they should run in easily.  You should only need a G-Cramp if you are forcing the fluid back up to the reservoir. If you have the block off the bike or have loosened off the banjo (thus spilling fluid all over the bike and stripping the paint etc) they sholld slide smoothly and easily.

You can get the pistons out by taking the caliper off the bike - but still on the hose etc, removing what you can and ten pumping the brake - the piston should run forward and then drop out in a puddle of DOT5.  Clean it carefully - want to polish it not remove metal, ditto the inside of the bore, and then rebuild.  Use some fluid as lube to run it together.  If the angles etc are right it can help to fill the piston with fluid and then run it up into the bore - cuts down the amount of air trapped inside.

If you need to use a hammer - something is wrong

Care and patience maybe on a few sheets of newspaper on the kitchen table with a cup of coffee - make sure you do not drink the fluid by mistake - it tastes horrid and is no good for you (DAMIKIJD) and the job is pretty simple.

Be careful with the banjo bolt and particulaly the bleed nipple - they both round off real easy and the nipple can break off.  I like to loosen the nipple with a tight fitting socket and only when it is free use a spanner on it.

R

[Olof.he]

Alright! Thanks a bunch!

I hope I've understood things right.

The pistons are only pushed into the caliper, and if you remove the whole thing, the brake pads and start  pushing the break handle, nothing will stop them from dropping out from the caliper, but all the fluid will follow too?

http://www.mainjet.de/shop/catalog/images/img_Bremssattel_XBR.jpg

Nr 11 and 13, are the things that easily get dirty and makes it impossible for the caliper to slide from side to side when gripping and the caliper will not be aligned or properly centered?

What I do NOT understand is: When pulling the brake handle the pistons go out and push the pads to grip the disc, but what is reversing them afteryou release the handle? Is it the vaccum of the fluid that just releases the pressure and it then it stops gripping the disc? Or does it pull back? And is it the suction that keeps the pistons attatched at all?

[steveD]

My understanding is that the piston rings are square and as the piston is forced out of the caliper it slightly distorts the piston ring which has enough movement in it to bring the piston back slightly. As the pads wear, obviously the piston will advance out of the bore more and overcome the sealing ring trying to pull it back, this is where the 'auto' adjustment will take place. Eventually the piston ring will wear and the important squareness will be compromised and if the rings perish and go hard the movement in the rubber material will not be sufficient to 'drag' the piston back.
That's my pennies worth and I'm sure our Jethro Stalwart will be on hand to either corroborate what I mention or dismiss it as a load of old Cr*p!
Oh yeah and I have refurbished calipers before and replaced rings successfully.

[SteveC#222]

The caliper rebuild is a pretty straightforward job but best done with the caliper off the bike. Check out the article on www.xbr.de as it takes you through step by step. Wemoto sell the seals and they used to sell stainless brake pistons which shouldn't corrode. Also check the caliper pins are clean as they tend to get gummed up with brake dust. XBR's are prone to the caliper seizing up so it's worth giving it a complete overall.

As always, if you're not sure what you're doing it's probably best to get your friendly local bike mechanic to do it for you - brakes are too important.

This video from youtube shows you how to replace the pads, it's actually a rear caliper but the principle is the same.  http://www.youtube.com/watch?v=X4K6sKLCGIs

[guest7]

Just a thought (from a mechanical idiot) but is the caliper able to slide on its mounting pin? (part numbers 11 and 13, as you have said) I'd check to see if the calliper is locked in place (corrosion between the pin and calliper body being the usual cause) then the calliper won't be able to move sideways and it may be seized in place too far to one side.

HTH (but fully expecting to be flamed for an inept question)

GC

[Andy M]

Just a thought (from a mechanical idiot) but is the caliper able to slide on its mounting pin? (part numbers 11 and 13, as you have said) I'd check to see if the calliper is locked in place (corrosion between the pin and calliper body being the usual cause) then the calliper won't be able to move sideways and it may be seized in place too far to one side.

HTH (but fully expecting to be flamed for an inept question)

GC

This is what the Triumph one does.


Andy

[guest295]

The mounting pins often freeze to the caliper; then the unit can't adjust to new pads. Break the pins free, clean them and smear them with anti-seize compound like Loctite's.