Both my rear disk breaks are showing a rather extreme abrasion in deep groves with thick rust building up on  some "rings" where there is no break pad contact. Both rear disks are showing almost identical wear patterns.

I've been looking at the rear disks of every polo I see to see if I can see it on any other cars. None.
 

I have taken it to my VW dealer before who said I should "just break harder". I've been trying this, but no improvement.

I'm now taking it back to them next week to see if they'll take a proper look (as still under warranty) but wanted any advice from here as to how I should argue my case. Total mileage is 25,000 miles.

 

does look like lack of use , if at anytime the car has stood and rust starts then it takes alot of braking to clear it off , have much the same on my golf 

 

theyre right that more use /harder braking would clear it off ...but theyre just consumables anyway 

I've just spent two weeks driving around Europe. I'd have thought that after all that daily driving and breaking they would have evened out, but these groves and untouched rings are still present.

hmm yeah , i dunno i think once theyve started to rust they dont really clean up like new

 

mine kinda always looked a bit like that ..what with the uk weather theyre often rusty overnight , then weekends or longer stood around

The back brakes don't really do much on these cars because of how light the back is, so rusty discs do happen a lot. 

 

It's worth having them apart and cleaning them up if you have the opportunity. 

 

I tend to use a very light amount of handbrake at low speed once in a while to keep them clean. Just coast the car forwards at 5-10mph and put enough on so the brake rubs but doesn't bite.

Thanks for your replies!

The rust I can appreciate - I often notice how easily the front rusts and clears (I hear it scrape off). @steveo3002, you raise a good point that if it's well rusted in it might not clean up like new - I can see that on the main rust rings - they have a "scraped rust" appearance.

I didn't know about the handbreak technique @Yeti, thank you, I'll give that a try. I had assumed the handbreak was a different contact surface, not the rear pads.

One remaining worry, which perhaps isn't so obvious from the photograph, is the deeper grooves that have appeared. I wondered if there was some grit under the pads, but their appearance on both wheels made me think otherwise.

 

 

It uses the pads on VW's (old fords used to have a separate drum in the disc, don't do it in a land rover with a transmission brake). It's not a perfect solution, it normally pulls one a bit more than the other (outer more than the inner I think). I wouldn't neccessarily use it to clean them up, but it can help keep them fresh. 

 

More expensive discs can rust a bit more slowly, but it's not really something you can cure. 

For a three year old car with less than average mileage, there does look to be fair amount of corrosion there - not only on the disc, but also on the calliper.

As said above, due to the weight, there isn't a lot of braking on the rears, but once you have groves like that in your discs, all the braking in the world isn't going to 'polish it out'.

The tip of applying a notch or two of handbrake is a good idea, but this is more of a prevention than a cure.

It would be interesting to see what the inner face of the disc is like - as that is somewhat more protected from the elements, it may have had a better life.

Cars living near to the coast can suffer more corrosion than others, but I see that you are in Cambridge.

If you make a warranty claim on this, don't be too surprised if they tell you that it isn't a manufacturing fault - which to be honest, it isn't.

If they do 'play ball' and change the discs for you, I would recommend that you get into the habit of doing the handbrake 'thing', but if not, and providing that the brakes are working OK, I would tend to just keep driving it 'till you do need new discs/pads.

 

Regards

washing the car and leaving it stood is all it takes , must say at times ive been a keen car cleaner and say if you wash the car then it sits several days its going to be rusty , acid wheel cleaners will make it wore