Car (the ****-stra) has just been in for two new front tyres. I had noticed that the brakes were making a horrid grinding noise and, having had the fronts replaced (pads and discs) in June, suspected the rears, not done for 30,000.

Sure enough, they reported rear discs pitted on inside.

But why? They are shiny on the OUTside, why have the insides pitted? And does it necessarily mean new discs?

 

Maybe pads not bedded in right when new ?

as far as i can tell its all down to choice , as long as car pulls up even and in time itll go through MOT , for eg

sounds ike youre down to metal on the pads though . I was told yesterday my offside rear caliper was totally fubarred - and god knows posssibly had been since they put new pads on 6 months ago.
This is because they are Aluminum ! and i live by the sea ...

 

My nearside caliper was sticking when I got the car, I could see rust deposits on the rear wheel. Maybe the other side is doing the same now? It's in for MoT tomorrow, so I'll know then.

 

I don't know why, but on most cars with standard sliding style calipers, the discs ALWAYS rusts up first on the piston side of the caliper (i.e inner). So the inner looks minging, whilst the outer looks fine.

Its mostly on cars that have light brake use or are used infrequently , parked over grass etc. at some point in their past. Essentially, for whatever reason it starts as a lack of braking effort/or use thats preventing the pads keeping disc clean, then once deep rust has established it will never self-clean without intervention (regrind discs or replace).

Once deep rust/pitting forms, it acts like sand paper rubs the pad down on that area, so it sees even less friction, so it gets worse and worse until it starts flaking.

IMO its one or a combination of two things; the way the car is used and stored and/or the caliper slide pins or pads sticking in their guides or some other issue thats reducing braking effort.

 

If the discs are thick enough, you can have them re-ground along with new pads, just bear in mind the labour required to so this often outweighs the cost of new discs.

 

Is there any way keeping an ali caliper working ok , apart from and maybe including stripping it down every month ?

 

Saw this, thought of you...taken half an hour ago. Golf Mk5 1.6FSi, front discs, ATE calipers:

NSF outer:


NSF inner:





OSF outer:



OSF inner:



Note pad backplate rusted around the guides, this means teh pad is probably stuck so most of the braking effort is on the outer side of the disc.


Rears are worse (TRW calipers) but cant get a decent pic because of the disc guard.

 

Mine is in for MoT now, he'll quote for new discs and pads.
Halfords, who were by FAR the cheapest for tyres, quoted me £155......the discs and pads are under £60 from Euro.

 

Failed MoT on rear discs and pads, metal to metal contact.

£97 tomorrow. That's £58 cheaper than Halfords. WHY, when they were so cheap for tyres?

 

you have answered your own question, they are cheep as on tyres, euro parts don't sell tyres so don't have to make up the tyre giveaways on other things