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Rear Brake Disc Corrosion

2.3K views 9 replies 6 participants last post by  The Aviator  
To be honest most manufacturers would have the same attitude. Just experienced an issue very similar on my CX-30 rear disks / rotors at the 1st MOT (Three years, 10,700 miles). The MOT inspector issued an advisory for pitting to the rear disks. He mentioned it was due to the low mileage. Having looked on line seems to be a common problem.
I had a similar mention as well. It particularly applies to vehicle, which are often driven underloaded, i.e. only the driver or the driver with just a front passenger and hardly any load in the boot. In these cases, the front brakes are sufficient to do all required work for stopping the vehicle and the rear ones are underused. This is, of course, applicable to normal drivers, not "boy races".
 
As my car was nearing 2 years old I booked it into my local Mazda dealership for service. The car had only done 10,700 miles. I have to admit booking it in with some reluctance as my dealings with this dealership has not been trouble-free, however I was given 2 years of free servicing from them at no extra charge when I bought the car, so in the car went.

So the service went OK, but not without the same communication issues found in my past dealings - the service department being almost unreachible by phone - ringing out before Reception taking the call back and having to take a note to either pass info on or ask for a call-back. Late on in the afternoon I got a call back to tell me the car was ready to collect. When I got there I was told the car was ready to drive away, but they found something during the EVHC (vehicle health check) was associated with the rear brakes and the work was advisory, however the report was not yet available but they would send it to me. As I was in a hurry I took the keys and went without further questions. Later on the health check came through and it was reported that the rear discs were corroded and replacement was advised, along with the brake pads (usual procedure). They gave costs for the replacements either with genuine Mazda parts or parts sourced elsewhere. Initially my feelings were of suprise as the car was less than 2 years old and had covered so few miles (though the car had never been left for any time without being driven). Suprise was replaced with irritation when the situation sank in but I took a couple of days to think things over before acting. It also gave me time to check out the rear discs myself and there does seem to be some corrosion there. Whether it's enough to require replacement is another question (I'm no mechanic). My reasoning behind my irritation was that though I accept that brake discs do wear out and are looked upon as consumable, however I would expect this would be over a far longer time scale and/or far higher mileage. Fair wear and tear if you like. For a car with such few miles under it's hood and being so young I fail to see how you could classify rear brake disk replacement as being due to "fair wear and tear". Brake discs should last far longer than this IMO. My view is the root cause is sub standard parts.

So today I went back down to the dealer (from my experience, phoning them is just too much hassle) and was told brake discs and pads do not come under warranty and they have never replaced any under warranty. I explained the above reasoning and my view that it should be a warranty replacement issue. They effectively brushed me off and told me to deal directly with Mazda. I did not leave before getting a phone number for Mazda. When I got home I called Mazda UK and was not told what the dealer told me, the person taking the call agreed that this did seem far too soon for brake discs to need replacement, however the person dealing with me was no expert and she would raise a case with the appropriate department and someone would get back to me within a week. So I guess I will wait and see what their response is.

My car drives well, and the parking brake seems to release and engage without issue. Hill hold also seems to work smoothly and general braking appears good and progressive.

I've seen the thread below on this forum but it was never stated if the work was completed under warranty or if the member paid for the work to be done, the mileage is almost double what my car has done as well.


I would have thought even 20K miles is a bit early for a rear disk to need replacing but I don't know if that was down to disc wear or corrosion.

I'll keep everyone updated on the progress but would appreciate any feedback on whether you consider warranty replacement in my circumstances reasonable or not, or if members have similar storys to tell on the rear brakes.
I had a similar MOT advice after 3 years, but no requirements to replace disks or pads at the rear. If you leave in the coastal UK areas the corrosion is bound to happen faster than inland. What contributes to it is a low mileage and amount of time you drive with not fully loaded car. If it is just you and a front seat passenger with no load in the boot, then the front brakes take the load under braking and the surface rust remains on the rear brakes. My car is parked outside all year round and this contributes to the rust issue as well.