Pan European back brake

[chunkolini]

Hmm.
Back brake had been binding a little bit after riding in the wet, nothing too bad just when backing out in the morning.
So pads off, clean pistons and copper slip everything. in theory.
I took the pads out, plenty of meat on them, undid the front sliding bolt so I could rotate the caliper back around the rear pivot and get at more of the pistons, Cleaned pistons with a toothbrush, put everything back together and nothing! no pressure at the pedal. The pistons are happy to move in and out smoothly, have to be eased back in a screwdriver, but not sticking.
Looks to me as though there is a lot of piston exposed 8mm? plenty of meat on the pads say about 5-6mm.
When I press the pedal the caliper seems to be trying to twist out from the front, and there is a small gap between the front of the inside pad and the caliper. I have bled the system.


First pic shows caliper from behind with the piston just touching the pad, second pice shows view from inside the wheel.

Anybody got any ideas what is wrong. Brakes were fine before I started fannying around.

Looking at the pics again it seems as though a shim on the opposite side to the pads would do the job, are the pads worn out? on other bikes in the distant past I have worn them down to paper thickness.
No parts were left out on reassembly

Chunko'.

 

[tigler]

In the top pic, is it the perspective or is the caliper skewed relative to the disc ?

 

[julianthegypsy]

I can't see anything obviously wrong, is it possible you got some air in there? Might be worth bleeding it out to make sure.

 

[stormin]

As tigler says looks like the caliper is not sat square to the brake disc. If so you are using all you brake pedal travel pulling the caliper back square and it's not applying any real pressure to the pads.
You've not twisted bend or cross threaded one of the locating pins by any chance? Sometimes they can become so worn, or the caliper bore that the caliper no longer slides on them properly but cants over at an angle and leads to spongy brake problems.

 

[chunkolini]

Just had another look, the caliper is square, I must have taken the shot prior to tightening verything up.
Press the brake pedal though and you can see the caliper moving out at the front.
Will have another bleedin' fiddle tomorrow.

I have had this before with disc brakes, fiddle fiddle fiddle ad infinitum, then come bck and bleed them again. Hopefully I dont have to get caliper off and remove pistons, that involves messing with half the exhaust system.

Chunko'.

 

[Tiggy_dorset]

Does the caliper slide left and right smoothly on its sliding pins? Best way to check this is to remove the pads and bolt the caliper up as it should be, then check that it slides left and right. It should slide on the pivot pin that you mentioned as well as the sliding pin that you 1st take out to remove the caliper. This pin usually bolts through a bush. This bush usually sits within a rubber boot or has a boot at each end and should also slide left and right within its caliper housing.


Also its known as bad practice to use copper grease for the pistons as it supposedly does the seals no good. red rubber grease for the pistons, but copper grease is ok for the sliding pins.

 

[chunkolini]

caliper sliding nicely.
There is a big bolt at the front that screws into the caliper and slides into the mount on the swing arm, and a smaller slider on the back end mounted on the swing arm.
Chunko'.

 

[mike os]

only got pistons on one side chunko?

seems a lot of piston sticking out there

I assume the brakes are independent?

 

[CKJDJK]

Did you put the pads back in the same order you took them off? The pads may have worn to suit the disc and if put backe on the wrong side may be rubbing against then unworn part of the disc.

there could also be air in the system. Put a length of clear pipe on the bleed nipple and make a high loop (but bellow the fluid level in the resivoir) with the open end submersed in a jar of brake fluid. Open the nipple while pressing the pedal. Hold down and close the nipple. repeat several times until no air bubbles show. If still no good. Open the nipple and leave over night. Any trapped air may migrate to the highest point.

Last option is to apply a little air pressure to the revioir by putting a bit of bicycle inner tube (with valve) over the top. Resivoir should be full. Use a bike pump to blow the fluid through. Keep the resivoir topped up above the min level or you will introduce more air.

Good luck

 

[chunkolini]

No fancy and pants linked brakes,
I did try putting the pads in back to front like a muppet ahem.
I will have a fiddle tomorrow.

 

[Tiggy_dorset]

In the first pic, is that brake fluid (possible leak) where the hose is crimped onto the banjo? Or is it just residue from when you bled the system?

When you bleed the caliper, its sometimes good to twist the caliper around in several directions to dislodge any trapped air. I had bled brakes over and over in the past and cursing as I was sure there was no air left, until I moved the caliper around. Sometimes air can find a hidey hole and refuse to budge until you move its home.

Also as Mike Os mentioned, is it independed from the front brakes? If it's dual combined braking, then you will have other bleed nipples in the system to include in your bleeding process.

 

[Robotstar5]

Leave pressure on the pedal (cable tie, weight etc.) overnight, it helps the bubbles migrate to the end of the system.

Remove caliper and hold above level of master cylinder while bleeding.

 

[chunkolini]

Done mostof these, taking the caliper off involves taking the silencer off, that can wait until we get desperate.

BUT!
Oi tink deyr'e fecked.
Just been down to the RatCave, pushed the pistons right back into the caliper, slid the caliper over to the right as far as it can go and they just about touch the disc. I reckon I was on the wear limit.
Dummy, the layer of sludge on the pistons was not that obvious so I assumed I was fine. I guess working on the limit that they reached slowly was fine, my messing about has left them unable to reach that limit.
So I have left the system open as suggested with the pedal to the floor and the pads in.
Tomorrow I will ride off like that and smack straight into my neighbours car.

I am awful tempted to make up a shim out of 5mm plate but that would be a stupid thing to do.

Then again in Africa, my pads wore out, these guys ran off with them and came back a few hours later with new pad material stuck on the backing plates. then they spent another couple of hours rubbing them on concrete to get them to the right size and I was fine. I asked what they were stuck on with, they showed me a tin of Evostick. Were they taking the ****? I expected to be killed within 10 miles, they pads lasted over 3000.

Lets see where we are in the morning. Cheers all.

Last minute thought for the day.
Shims?
Why in hell did Mary Poppins and Dick van Dyke sing a song about shims?

Chunko'.

 

[Bingy]

My V-Raptor rear brakes were the same. After taking it for a pre mot, the mechanic told me to take the caliper off, turn the caliper upside down so the bleed nipple was at the top instead of the bottom when mounted on the bike, stick a spanner in between the pads and the re bleed and watch all the air come out. Then remove spanner refit and try brakes, if not repeat.

Worked first time for me. HTH

 

[the snooper]

you havnt left any shims out have you chunko there is a lot of piston out

 

[gordon stephenson]

My Land cruiser does exactly what you describe if the pistons are forced back and the fluid goes back to the master cyl, Don't know if it upsets the abs or what, takes ages to get it right again despite lots of bleeding,What I do now when the brakes need seeing to is clamp off the flexible pipe on the wheel being worked on,open the bleed nipple,fit rubber tube and expel the fluid as the piston goes back,And never had any trouble since using this method,

 

[Wedg1e]

I seem to think that the rear caliper on my ST13 (same pads as the 1100 and a similar caliper albeit with linked and ABS) does show a lot of piston even with new pads fitted... and even new pads only have a few millimetres of friction lining on them, as I discovered with my old '11 when I bought new pads only to find they were just as thin as the old ones!

 

[chunkolini]

Curiouser and curioser.
Cheers for the image Mr Snoper,I looked at a new set of pads, about 2mm thicker, so yes a lot of piston showing.
After another fiddle about today I took it to a small mechanics in hereford for a second opinion. I was there from 11.00am to 3.00pm acting as second spanner and labourer.
The caliper is fine, no air in the system, but still the caliper could be seen trying rotate in at the back.
The aluminium mounting bracket that the caliper mounts on pivots around a large bolt that threads into the swing arm at the front, there is about 8-10mm of space between the bracket and the swing arm, this is allowing the bracket and caliper to swing round. It looks as though the mounting bracket is bent.
Weird. Last night I did not touch the mountings between the bracket and swing arm, the brakes were fine until I started cleaning them up, I cant remember leaning on or forcing the bracket, it is a great big thing that I would remember bending.
The bracket is the big plate in the picture.

In the end we worked out between us that this is the problem. I asked how much I owed him. he said 'a tenner I didn't fix anything' I offered twenty quid and got sent packing. I have to take these boys some cider as a thank you. All praise to small guys working in sheds. I feel quite humbled by this kind of thing.

Does anybody have this bracket for a 97 pan, base model no abs or linked brakes.

Chunko'.

 

[Tengtooltom]

Attach a length of plastic pipe to the bleed screw on the caliper and attach a pump type ( new and unused for oil) oil can of brake fluid. Open the bleedscrew and pump the fluid back up into the reservoir. Thats how we bleed the clutch and brake setup on of the Case/International tractors. It never works to bleed them the conventional way.

 

[stuvy]

Glad to hear its fixed buddy, i hate being without a bike, really need to buy some more parts for my gas gas project!!