Corrosion on rear brake disc

[Craigbarnley]

Just had my cars mot done and it has failed because the rear disc is corroded? I thought this was a common problem !now having to have new rear discs!

Anybody else had this problem?

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[GlanzaV]

Corrosion on the face? That's usually light surface rust that burns off through braking?

If the disc is extremely worn though and the rust they are talking about is fouling on the caliper then they might deem that as excessively worn.

 

[Mattwood]

my rear disks were highlighted at my last service as being excessively corroded on the inner edges. I will be replacing them as soon as the weather gets better.

 

[DPJ]

You'll also get damaging corrosion on disc faces when the pad hasn't been touching properly (because of sticking piston etc)

 

[GlanzaV]

It's a fairly easy job and there is a guide on here in the info base. Worth doing yourself for the money dealers will want for it.

 

[Orion1969]

My rears are also bad, id say a good 10-15mm around the outta edge. Its passed 3mot's like that so im thinking its down to the tester being more of a 'Fail' vs 'Advisory' sort of guy. Mind you dont all MK4's, Polo's & Fabia's suffer from this...design fault? (because of the small footprint of the pads)

Now ive said that mine will fail in March

 

[krussel]

I left my car standing over the xmas bad weather and noticed the rear disks went really bright orange / brown.

I decided the take it out to clear them and i had just got going when a delivery van pulled out of the kerb right in front of me, i hit the brakes hard and ................... nothing bloody happened

After that i drove a couple of hundred yards with the handbrake lightly on (donging all the way ) and the brakes where fine after that.

Of all the cars ive had, including a Polo, none corrode like this MK4 beezer

 

[GlanzaV]

My rears are also bad, id say a good 10-15mm around the outta edge. Its passed 3mot's like that so im thinking its down to the tester being more of a 'Fail' vs 'Advisory' sort of guy. Mind you dont all MK4's, Polo's & Fabia's suffer from this...design fault? (because of the small footprint of the pads)

Now ive said that mine will fail in March

I'm sure they pretty much put a gauge on the disc and if it is thinner than the limit (not sure what it will be) it will pass/fail.

Unless of course like I said at the beginning it is actually fouling somewhere?

 

[Nath.]

I'm sure they pretty much put a gauge on the disc and if it is thinner than the limit (not sure what it will be) it will pass/fail.

Unless of course like I said at the beginning it is actually fouling somewhere?

This is the common MK4 Ibiza fault That the OP is talking about

Evidence of poor pad to disc contact is an MOT fail. No amount of driving with the handbrake on 1 or 2 clicks will fix this. It should have been spotted a long time ago and then maybe the handbrake trick will work.

 

[Orion1969]

^^^ you been in my yard taking pics of my discs

 

[bald_eagle]

I left my car standing over the xmas bad weather and noticed the rear disks went really bright orange / brown.

I decided the take it out to clear them and i had just got going when a delivery van pulled out of the kerb right in front of me, i hit the brakes hard and ................... nothing bloody happened

After that i drove a couple of hundred yards with the handbrake lightly on (donging all the way ) and the brakes where fine after that.

Of all the cars ive had, including a Polo, none corrode like this MK4 beezer

Thats a bit strange, on my car the fronts do most of the work so having corroded rear discs wouldn't have left me with no brakes.

 

[DPJ]

Thats a bit strange, on my car the fronts do most of the work so having corroded rear discs wouldn't have left me with no brakes.

You're overlooking the fact that a rear pad suddenly moving a distance towards the disc can take up most of the action of one brake pedal push.

Similarly, a rear pad stuck on can boil the brake fluid, giving a sudden no-pedal.

 

[Nath.]

^^^ you been in my yard taking pics of my discs

Hope you don't mind me using them, I couldn't find the pics of my old mk4 rear discs.

 

[krussel]

Thats a bit strange, on my car the fronts do most of the work so having corroded rear discs wouldn't have left me with no brakes.

Oh iam sure the fronts were just as bad and thats why it did not stop

I did a few hard pull ups when i got the chance to clear the fronts