Odd front brake disc wear pattern.

[MIG Wielder]

Hello All, What has gone wrong here do you think please ? This is on a daily driver 1850 Dolomite and the outer 1 inch radius of the disc is horribly pitted & rusty; worse than anything I have seen on anything that has been laid up for years. The pads are nearly new and are NOS Unipart and are fairly flat over most of the operating surface. And the calliper pistons are both moving freely in and out. The brakes just feel good and solid on the road. The offside disc is fine.
So what is causing the pads to run on the inner 2/3 of the disc and why aren't they cleaning the outer 1/3 of the disc ?
Thanks,
Tony.

[tamtrucks]

has the disc got the same thickness throughout the braking surface? could your bearing need replacing or excessive play

[Carledo]

I change out discs like this all the time Tony, mainly on MOT failures. Classics, modern, single, vents, front, rear, RWD, FWD, there doesn't seem to be any common cause for it, it just happens! And generally speaking, there is a confusing lack of imbalance when the car gets to the rollers too!

Steve

[TrustNo1]

Piston not pushing out square with pad.

[tony g]

Piston not pushing out square with pad.

I thought that too. Also if the pad gets jammed in the caliper and tips slightly towards the end of travel it could cause this. I would expect the pad to be slightly tapered there too.
Tony is the inside face of the disc clean?

Tony

[dollyman]

Like Steve say's, i have had the same thing on many cars, and like you only one side. More often than not it will be an advise on the mot as it does not cause a brake in balance.
Personally if its not causing a problem? I would leave it What would others do?

Tony.

[GTS290N]

Personally I think the braking surface is small enough without adding to the problem....

[Carledo]

More often than not it will be an advise on the mot as it does not cause a brake imbalance.

Tony.

There seems to have been a change in DVSA's instructions to testers concerning just this fault in the last 18 months or so. Where it used to be acceptable or just an advise in the past, it is now a reason to refuse. As witnessed by the huge pile of brake discs in my scrap pile! They are actually beginning to outnumber broken coil springs!

Steve

[dollyman]

More often than not it will be an advise on the mot as it does not cause a brake imbalance.

Tony.

There seems to have been a change in DVSA's instructions to testers concerning just this fault in the last 18 months or so. Where it used to be acceptable or just an advise in the past, it is now a reason to refuse. As witnessed by the huge pile of brake discs in my scrap pile! They are actually beginning to outnumber broken coil springs!

Steve

Probably my guy being helpfull, but i have to say if he comes up against any of the newer vented stuff with the same problem....... They do end up with the spring's.

Tony.

[MIG Wielder]

Hi All, Thanks very much for all your comments and hints as well. I was also thinking along the same lines as wheel bearings, ( they were a bit slack) and brake pistons skew but they seemed to be moving O.K. Anyway, seeing as its MOT time coming up I've just added the old disks to my own pile of scrap metal.
And yes, the inside surface was just as bad as the outer surface. I was wondering about Winter road salt, but we didn't get a lot of that spread round here last Winter.
Tony.

[TrustNo1]

can't be failed if it can't be seen

(kinda written in jest)