Rear Disc Brakes Corroded

Hi All,


I took my car for its 2nd service yesterday, and was utterly surprised when they told me that my car needed urgent attention due to the rear disc brakes been corroded. The car is 2 years old and has done 12,000 miles. had a bit of a look around on the internet to see if this is a regularly problem and I am aware if the car stands around for a while that obviously that does not help. I only have one car and commute to work and back Monday to Friday, all year, apart from when there is a couple of inches of snow on the ground. So it does not stand around. The brake pads on the back are 30% worn according to the service report, and the rear tyres have about 2.5 to 3mm of tread still on them. The garage have quoted nearly £400 for the replacement.   I am utterly dismayed, in all the years I have been motoring and all the cars I have had. I have never know the disc to wear out so quickly, sorry corrode. Certainly never quicker than the pads and the 1st set of tyres. Has any one else had this problem or can give me any help or advise.


thanks in advance for any help




I’d take it somewhere else for a second opinion.

Rust on the disks isn’t unusual, in fact my wife’s Mazda 6 leaves little flakes of surface rust all over the garage floor from the very outer rim of the disks and never had an advisory on any MOT. All disk brakes have surface rust which is worn off by the pads during driving, leaving a small section above and below the area covered by the pads. As long as it doesn’t look like a blacksmith’s anvil, I would say it was normal. After washing my car, I leave the handbrake off if it’s going to be stood a few days to prevent the pads binding. It means I come back to an orange bloom which gets cleaned off by the time I’ve made Morrison’s - a couple of miles away.

A couple of pics might help, but I would say the garage is lifting your leg.

Mazda discs are prone to surface corrosion, my first MX-5 was quite bad as it lived outside and was a daily driver all its life and I changed to EBC discs but that was after 50k, my current car is cossetted in the garage and only a toy so has fared much better, no visible corrosion after 30k.

Rear inner faces are usually the first to corrode, a mix of braking balance and location it would appear, its common on many cars but 12k seems very early to be worth a comment in the report, definitely worth getting a second opinion.

Your rear tyre wear sounds as though you are enjoying the car , if it were still summer it might be worth swapping them front to rear but it looks like a new pair are in order for the winter.


This does not sound right. Assuming the rear brakes are working correctly and car in more or less daily use, corrosion should not build up on the brake discs where the pads act.

My advice to you is to visually check the discs - you should see a nice shiny sweep throughout the entire circumference of all 4 discs where the pads contact on braking. If it looks a little discoloured, take the car for a drive, use the brakes a bit  and then re-check.

The garage are indicating that there is corrosion present on the rear discs that cannot be cleared by the brake action. In this case the only real option is to replace both discs and pads. This scenario does seem extremely unlikely as it would require a reasonable period where the car was left outside with rain getting to the discs and no use to allow a serious corrosion(rust) build up and pitting - we are only just out of summer!    



Discs are cast iron…so depending on the quality of the metal it’s the norm.

All my cars with discs do it if left even for a day outside, especially after washing.

Mx5 rear discs? They don’t really get worked much (actually not good) which is why I have, for 14 years habitually pulled the handbrake up a couple of clicks on the move on both our 5’s to give them a bit of “exercise”. Nor do I use the handbrake over night…they are both garaged. If that sounds eccentric, then  witness how I only had to put on fresh rotors & calipers on our Mk2.5 6 months back with 96k on the clock…on a car that gets “used properly”. Did the same with both my Opel Monzas, Capri Injection with rear disc conversion…and pretty much everything else. The rear rotors on my Mk1 are fine after 10 years.

Best thing to do with 5’s in my opinion & experiences is take them out once a fortnight or so for a bliidy good caning…around a gallon’s worth. It’s what they are designed to do after all.

I work in a Motor Factors and do the warranties corrosion on the outer edge of the disc can be because some suppliers add an extra edge on the rim on the discs so they can add their parts numbers batch codes etc…these area are very prone for crumbling in big bits on some makes within months

It’s not uncommon for dealers to pull the ‘You need new brakes card’

They tried something similar with me, telling me my pads were 60% worn, my reply… so I’ve 40% left then.


Of course where brakes are concerened, you need to ensure they are operating correctly, absolutely no skrimping in that department.

If you have an axle stand or decent blocks  and know how to remove a wheel, then your own visual inspection, plus post some pics up here should give you the definitive answer to whether or not the dealer is trying to pull some wool over your eyes.


A set of OEM quality rear discs plus pads (Mintex/Pagid/Eicher) will set you back about £100 - £120.

Less than an hour per side to change them if you’re half decent with a spanner and socket set.

You might require a brake rewind tool, but these are only about £20, so even factor in the purchase of that and your’e still £250 better off in your pocket.


If it turns out that it’s just rim corrosion, then a quick descale will suffice.

Some MOT testers will flag up this even if it’s only the centre, unpainted portion of the disc (i.e. the unswept area) showing surface rust and the disc itself is totally safe. It’s possibly more a cosmetic than a functional issue.

The rear discs on my 1998 Mk2 are possibly the twenty year old originals and were rusty when I bought the car. I bought a pair of new discs and pads when I serviced the brakes but when I looked at the old ones closely they are perfectly serviceable, even though they looked quite shabby.

I cleaned them up and measured them, found they were well within the minimum thickness limits and put them back on with the new pads. I saved the new discs for next time. The car has passed the MOT with no brake issues twice since.

Corrosion can happen.  It did  on mine, not with daily driving, but only because I needed to leave it in the long-stay carpark at Gatwick for a few weeks.  The rear disc surface facing the prevailing wind was the worst and I needed to skim that.  The other three surfaces just cleaned up on the lathe with an emery pad.  The extra braking on the fronts during the drive home had cleaned them up, but three weeks later the rears were still bad, hence the skim.  The improvement in ordinary braking with clean rear discs and new pads was astounding.

Some pictures here. (Forum Link updated 09/06/2021)

This coming winter I’ll be putting some el-cheapo wheel covers over them during the carpark stay. I’ve added some nylon string ties and curtain weights (to help with throwing the string ends around) to the little retaining hooks so I don’t need to reach behind the wheels…


Thank you every one for your help and advice, a few of you have said a photo would help. I do have a photo that the garage have sent me on the inspection report. As soon as i get my thick skull around working out  how to attach it to a post on here i will.

once again thanks 


 My dealer mentioned my rears were corroding a bit on the inside edge at its 2 year service (roughly 16k miles).  Now at the 3 year service (22k), the rears have about 15mm of the rear discs showing corrosion and pitting, and the fronts are just as bad.  I was quoted £774 for new discs and pads all round.  The inside pads on the front are 90% worn, and the rears are 80%.

Pretty shoddy if you ask me, I would not expect discs to be this bad at 3 years/22k.

Will need to get them done though, but not keen on OEM parts now the warranty has all but run out, what are people’s recommendations?

i don’t do track days, but when I do use the car, I tend to properly use it, so all 3 pedals get lots of pretty heavy use!!


Mintex, Pagid, Eicher.


don’t forget to apply the daily discount voucher.

If they don’t have one, come back tomorrow.

Main dealer I’m guessing. I had this for years on an Astra, every service in the 1st2 yrs they came up with this one (front pads/discs worn) and I ignored them 'cos I measured the pads regularly and I knew how long they lasted.

At about 70k I got them to eplace the cambelt (a good price at the tome) and they insisted on doing a safety check, at which they pointed out several things including (you guessed it) the front pads!

By this time I was well annoyed, got a micrometer,measured the discs, measured the pads, wrote to VX to complain about the garage (among other things they said the spare had 7mm of tread, it was 3mm! and the rear wiper was worn - it was brand new). Upshot was a loooong interview with the garage chains regional manager, and a free set of front pads and discs. Which my local garage fitted for me at about 100,000 miles!

I also had the same at kwikfit when the car went in for another item, free brake check blah blah blah. Halfords, later the same day, checked and found no problems at all!

You can see for yourself if the discs are corroded. Even if they are, my friends local garage always advised him to give his old jeep an italian tune-up on the way to the MOT, to make sure the brakes weren’t rusting. Worked a treat.

Context for cost? my local garage has just replaced both front calipers, and the pads, when one of the calipers started binding on my '07 NC (just turned 100,000 miles!). Total bill £399.42. They usually replace the  pads for less than £100 each end, unless I ask for Mazda pads which brings the cost up to £100.

@Keat63, it is more the discs I am after.  They are definitely badly corroded, I have seen the service video my dealer does, and you can feel it with your fingers.  I quite fancy some of the EBC ones, but nobody seems to do them for the 2.0l ND.  Mx5parts have the ones for the 1.5, or the OEM Mazda ones only, and can‘t find any suitable discs on euro…

EBC Part number D2033

If you want to call I can send you a set. 

So, still researching discs and pads…  thanks for the heads up NickD on the EBC fronts, but I need rears as well, and having emailed EBC direct, they have a part number for the 2.0l rear discs, but no timetable for actually making them!

Apart from Tarox (too expensive) I cant find any 2.0l rear discs anywhere at all apart from the Mazda ones, and given how badly mine have corroded I don’t want to go that route!  Anyone any ideas?

And while I am on, I am assuming that putting EBC discs (they only do standards though, not drilled or grooved) on the front, with either Greenstuff or Yellowstuff pads, and leaving the existing corroded rear discs on with some cheap pads until EBC do the rears is a bad idea?


I had to replace all discs on my 2002 car after two years, they were badly ridged. Replaced with Mazda sets, and then replaced by ditto from MX5 parts. Front brake discs are now ‘badly corroded’ (MOT test) on the inner surface and need more new discs again. I’m not particularly hard on the brakes, ( though I do remember at least two ‘panic’ situations) so that plus standing around for the last few years means rust is slowly advancing all round. Just had new front pads fitted, so it’s crunch time for new discs, or the discs will wear out the pads faster than I care to think about. The old pads were badly worn on the inside pad, while the outside of discs and pads were fine. Par for the course, I figure. (You can’t get the wood these days! - or good steel either.)

The wear on the inner surface of the front discs is an issue on the pre MK3 cars.

At my MOT a couple of weeks ago I asked the garage to check the rear brakes, since the hanbrake didn’t seem to be holding as well of late.

Car passed its MOT ok, handbrake efficiency was within limits. But when the garage stripped the back brakes down to check the handbrake operation they found the inner faces of the discs to be somewhat corroded! Hidden by the splash plates it seemed. So I had the discs and pads replaced, much better now.

When I collected the car they showed me the discs - and my reaction was “blimey, have I been driving on those?”. Inner surface apartfrom a narrow track in the middle was just a pile of rust.

Car is 12 yrs old and 100k miles or so, and I think they are the original discs. But I’ve only been covering 4-5k miles in it the last few years so along with a seized front caliper recently (its replacement cured a long-standing puzzle about intermittent steering problems) I think I’m not using the car enough!