Rear brake binding

Could someone with experience of rear brake issues have a look at this and make a suggestion please otherwise it looks like new calipers..
So here is the problem. As far as I am aware both rear wheels rotated with similar effort if rotated by hand when renewing upper ball joints (these ball joints have nothing to do with the problem).
Unfortunately on the last occasion the car was driven into the garage the handbrake was left on for several weeks. On releasing the hand brake the car was difficult to push and it became apparent that the off side brake is binding.
So the caliper was removed, pads removed, piston rotated 1/4 turn and pressure applied by G clamp to ensure it was retracted. The piston was stiff to turn.
On reassembly the wheel could be turned by the pressure of one finger pressing down on a wheel spoke. The pads must have been hardly contacting the disc.

Test drive this PM confirmed that the foot brake works. Application of the handbrake on a moderate hill was ineffective to start with but a few more attempts improved the situation. Back in the driveway and after jacking the car up the application of brake pedal prevents wheel rotation , releasing the foot brake and applying the handbrake starts to stop wheel rotation by hand. Conclusion foot brake and handbrake work.
However, the pressure or force required to rotate the wheel is greater (notably greater) for off side than for the near side.
Car passed MOT a few days before.
Any suggestions please?

Well it's hard to tell without looking. Leaving these cars that , let's face it are getting on , with the hand brake applied for a lengthy period is a usual way of finding that the calipers internals are in need of servicing or complete replacement. With all the weather we have endured lately it's not surprising that rust has likely taken hold and cased this .

The rear calliper are more complex than the front, which can be serviced, with care, using standard tools & a liberal amount of concentration plus a healthy dollop of that care I’ve just referred to; your life depends on it being done correctly.
The rears combine the standard piston system with the handbrake & an automatic handbrake adjustment mechanism.
These can be serviced on the bench, all the parts are readily available including the needle roller bearings in the leaver assembly in the eccentric chamber; it is this chamber that is the main problem, it fills with water & all the grot that is carried by the water.
Do not listen to anyone who tells you that WD40 will cure the problem, it won’t. It will expel moisture but it leaves behind a sludge & compounds the issues
The callipers can be cured only by taking the lot to pieces & rebuilding them with new parts.
However you need long pronged circlip pliers, which were available but we’re not cheap, I can’t see that situation having changed.
Everything has to be bob on as you don’t want half a day out with the undertaker plus once you have avoided this you want many more MOT passes along the road.
If you decide to rebuild, one tip, use a compressor to blow the piston out of the callipers, always use new rubbers, use the proscribed grease & cleanliness cleanliness cleanliness.
M

You have done the right thing by turning the piston a quarter turn but im wondering if it has corrosion on the mating surfaces if it was more difficult to turn than expected and has not helped with the problem. As Airportable says the caliper should be disassembled, cleaned and new rubbers fitted. If you doubt that caliper though I see that 'Bitz are doing refurbished rear calipers for £ 60 a side at present which may be tempting

I only tooled up as I had an f & tf at that time & refurbished callipers were not as accessible or “inexpensive “.
I had a spare set which were always ready to go on if required plus my favoured parts supplier is in Burnley, an unfortunate town I pass through on my way to greener pastures.
I wouldn’t have bothered with all the faff if a referbed set were more “price accessible” at that time.
M
M

I suppose there is another possibility and that is that the near side isn’t working as it should although that said it passed the MOT a few days ago.
Looking across from the off side (but not measuring disc thickness) the near side rear disc looks to be worn on the inner side .
Perhaps the mechanism on the near side piston has reached its maximum available travel.

Looks like a case for taking the infra red temperature measuring gun and comparing disc temperatures and ideally with those of a similar car.

Its not uncommon for discs to wear more on one side of the disc than the other. On standard single pot sliding calipers this is usually caused by the caliper not sliding correctly hence putting more pressure on one side of the disc before the assembly moves enough for the opposite pad to apply any pressure. Remove the caliper from it's carrier, check all meeting surfaces can move freely and especially the state of the tubular sliders as they can get gummed up over the years . Clean it all with brake cleaner or degreasant, bolt the caliper back into place first without the pads to check it can slide freely, then refit the pads and you should be ok.

Well, filled with curiosity and reluctant to jack the thing up again and remove wheels I attempted to measure the disk thickness by reaching between the spokes with a digital caliper.
The “good one - near side” was slightly thicker than the “binding one” on the off side, and even though slightly worn both appeared to be thicker than maximum.
Now I appreciate that the method is prone to error but it would seem that the binding brake has worn away the disc marginally more than the other side which is logical.
As both appear to be smooth and more than thick enough they must be good to go.
Pad thickness was not measured but looked as though there was plenty to be going on with. I do not believe there was a wear groove in these pads - so no idea as to the source.
None of this explains why the wheel was free to rotate in Oct last and now it is not even though the use has been minimal (only test run after changing suspension components after which the handbrake was left on for weeks in error)..
As the piston was re set by winding it in a 1/4 turn (with an angle grinder disk locking tool. - fits the piston exactly) why should the thing suddenly bind?
Yes, rotating the piston back in took a bit more effort than expected but let’s not forget that axial piston movement is minimal under pressure and as far as I am aware the means to relax that pressure is derived from return springs in master cylinder and the twist in the caliper piston seal itself.
Any thoughts will be gladly accepted.

A pound to a penny, your problem will be in the eccentric chamber. The spring will not be powerful enough to overcome the resistance created by problems in there; there is every possibility of the needle roller has corroded & collapsed.
M

I wondered for a moment there if the Eccentric Chamber was a section of the forum

All the T-Bar is an eccentric chamber & it looks like most of us are locked in!

Guilty as charged :woohoo: