Rear pads small contact on disc

[Souster]

Hi guys,

Just looking into my rear brakes as the were an advisory on last mot. The inner pads seem to be having good contact with the discs, no issues at all. Yet the outer pads on both rears are barely touching the disc (and hardly worn). I thought it may have been a sticky piston due to having the same on a previous lr, yet it isn't. Calliper seems to be functioning fine.

http://s905.photobucket.com/user/souster4/media/imagejpg1.jpg.html?filters[user]=109140969&filters[recent]=1&sort=1&o=0

As you can see in the picture, the disc is quite badly corroded on the outer edge. The outer pad on the one wheel i have looked at, also seems to be sitting lower than the pad on the inside.

What do you suggest i do. And what causes this?

[Souster]

Anyone have an idea?

[Snagger]

You need new discs and pads at the very least, and quite probably a calliper rebuild or replacement. I'd go for rebuilding the callipers with Zeus Engineering stainless pistons. The wear and rust pattern on the disc suggest that the pad has much of its material broken off, though it may be that the callipers are so rusted that the outer part of the pad is seized and the inner is pivoting against the disc, rather than the whole pad floating evenly. The callipers certainly appear to need a good clean up, even inf the pistons and seals are good. Fitting new pads alone will result in them being eaten away on their outer portion where the rust is rough, and being back where you are now. I wouldn't drive the car in that condition as the insurance would probably be invalid if you had a knock.

[Souster]

You need new discs and pads at the very least, and quite probably a calliper rebuild or replacement. I'd go for rebuilding the callipers with Zeus Engineering stainless pistons. The wear and rust pattern on the disc suggest that the pad has much of its material broken off, though it may be that the callipers are so rusted that the outer part of the pad is seized and the inner is pivoting against the disc, rather than the whole pad floating evenly. The callipers certainly appear to need a good clean up, even inf the pistons and seals are good. Fitting new pads alone will result in them being eaten away on their outer portion where the rust is rough, and being back where you are now. I wouldn't drive the car in that condition as the insurance would probably be invalid if you had a knock.

Thankyou for the reply. I'll change the discs and pads then. If the pistons appear to be working well - would it be bad to leave them? As long as i clean up the calipers?

[Snagger]

If the pistons are moving without restriction or leaks, there is no reason to replace them. Look for thick rust scale build up in the calliper body at the each end of the void where the ends of the pads slide - as I said, the pads may be binding on that scale and having their movement restricted. You can chip that rust off with a hammer and small stone chisel, and then wire brush the calliper before painting with calliper paint or Hammerite (I have used the latter on 8 callipers with good results).

http://www.nickslandrover.co.uk/defender-discovery-i-and-range-rover-classic-brake-calliper-overhaul/

[Souster]

If the pistons are moving without restriction or leaks, there is no reason to replace them. Look for thick rust scale build up in the calliper body at the each end of the void where the ends of the pads slide - as I said, the pads may be binding on that scale and having their movement restricted. You can chip that rust off with a hammer and small stone chisel, and then wire brush the calliper before painting with calliper paint or Hammerite (I have used the latter on 8 callipers with good results).

http://www.nickslandrover.co.uk/defender-discovery-i-and-range-rover-classic-brake-calliper-overhaul/

Thanks very much snagger. Pistons are moving freely on the wheel ive checked, so a good clean and wire brush should have her braking well in no time. Thanks again

[Mo Murphy]

Looking at the pic on my phone it looks like the caliper has worn where the pad sits in it allowing the pad to sit too far into the caliper. There appears to be a rusty witness Mark or groove on the shoulder of the disc where the pad has dropped through far enough to run on it.

If this is the case then replacement calipers are the only answer.

HTH

Mo

[Souster]

Looking at the pic on my phone it looks like the caliper has worn where the pad sits in it allowing the pad to sit too far into the caliper. There appears to be a rusty witness Mark or groove on the shoulder of the disc where the pad has dropped through far enough to run on it.

If this is the case then replacement calipers are the only answer.

HTH

Mo

On the outer pad closest to the wheel what you described seems to be the case Mo. Would this not happen to both sides of the caliper? The one side of the pad seems to be falling through so to speak. Just what you describe. At 130000 i cant complain i suppose. Thankyou

[Mo Murphy]

Not necessarily to both sides but the caliper is scrap anyway. Buying good second hand calipers for pennies and rebuilding them is very satisfying and cheaper than new

Mo

[miketomcat]

Not your problem but I find running without inner dirt shields the inner pad wears a lot quicker that the outer. I can only think it's to do with cooling.

Mike

[dailysleaze]

Mine were doing this. I changed the discs and pads, flexi hose for stainless, and pistons in the calipers for stainless, but it started doing happening again on the new discs.

Must have been the calipers. It might be the holes of the retaining pins getting larger allowing the pad to "drop" towards the centre of the hub

[Lewis]

I don't think I've ever seen a land rover winch didn't do that, I assumed it was just one of those things they all did

[Mo Murphy]

Trouble is that that pad rubbing on the shoulder of the disc wears a groove in it, ultimately separating the bolted part of the disc from the braking part.

That could be entertaining

The groove on mine when I got round to changing it was already 3/16 deep !

Mo

[Snagger]

Looking at the pic on my phone it looks like the caliper has worn where the pad sits in it allowing the pad to sit too far into the caliper. There appears to be a rusty witness Mark or groove on the shoulder of the disc where the pad has dropped through far enough to run on it.

If this is the case then replacement calipers are the only answer.

HTH

Mo

That could be the case and would explain it, but the amount of wear required to do that is considerable. I would clean up the calliper first, remount it and fit the pads back in to see if the inner radius of the pad is close tot he disc's shoulder/step/whatever you want to call the bit that extends towards the drive flanges... If it's in contact, then you have a problem, but new pads might be enough to remove the contact if it's the pad ends that have taken most of the wear rather than the callipers.

My 109's Discovery front axle had a similar wear pattern on the discs, but the calliper rebuild with new pistons and pads has not reproduced any defects on the new discs, even though the calliper bodies were reused.

Fingers crossed! Personally, I'd take the old callipers, after cleaning them up, to a LR specialist and compare them to a new calliper, fitting pads to see how much the tag protrudes in each calliper with the same new pad (you need new pads anyway) to determine if there is significant calliper wear.

Whatever you do, make sure you buy good quality parts. There are plenty of cheap callipers and other brake parts out there, but the lives of your passengers, other road users and yourself are worth the cost of doing it properly.