Pulling to offside under braking

[rossbraithwaite]

I have pulled the brake pads out of the nearside calliper one by one and replaced with a piece of wood slightly thinner than the pads. I could see that both pistons moved under pressure from the pedal but the inner one appeared to exert significantly more pressure. On removing the outer cylinder the head of the piston was quite tight in the calliper casting. Is this normal or should they be completely free? It may just have been brake dust build up causing the tightness in which case I wouldn't ecpect it to affect the piston's ability to move. is it safe to apply copper slip to this area?
Thanks

[Hugo]

If it's giving you the run around, I would put it on a rolling road & do a brake balance test to make quite certain it's not the rears.

[Tom W]

Putting the rears on a rolling road to test the brake balance isn’t a sensible idea if you have a limited slip diff.

[Hugo]

If the brakes are in balance it won't make any difference.

[Tom W]

And if they’re not, which as you suggested is a possibility, you’ll damage the diff.

[Hugo]

At least you'll know ;). Why should it damage the diff? It is, after all, a 'diff'. What happens when you go round a corner?

[Tom W]

I expect you’ll wear out the clutch pack. If one brake works and the other doesn’t, the speed differential between the wheels will be much greater than is experienced on the road. There’s a reason the MOT test uses a road test for cars with a limited slip diff.

[Hugo]

Even if one side is completely inoperative, which is extremely unlikely, you're not going to wear out the clutch in a five second brake test. More to the point, if the front brakes are in balance, it suggests the fault is at the rear, so if you think the diff clutch is that delicate, you don't even need to test the back brakes.

[Tom W]

I don’t know what point you’re trying to make anymore Hugo. If the fault is expected to lie with the rears, using a brake test roller to find it isn’t going to do a limited slip diff much good.

[Hugo]

My point is a simple one - that a five second brake balance test is not going to do it any harm either.