Rear brake corrosion

[Red_Corolla]

Hi Folks,

I wanted to direct a question at anyone who bought a Corolla (or any other Toyota model) within the last couple of years or so: How are your rear brakes faring, in terms of condition?

To explain myself; my Corolla is approaching 2 years old now and the rear brakes were looking quite nasty, having never bedded in properly IMO. I went through the exact same issue with my previous car (a Skoda) and, after consulting the owners' forums, it turned out that many others were having the same experience. The general consensus was that poorly manufactured discs were responsible, so I approached the dealer and persuaded them to replace the rear brakes under warranty. Sure enough, the replacements bedded in lovely and the corrosion never returned.

Having had that experience, I'm just wondering if I'm now going through the same thing with this car and thinking about the possibility of manufacturing quality being to blame rather than simply the way I use the car, hence the appeal for your comments. For now, I've cleaned up the discs and de-glazed the pads in the vain hope that they'll bed in this time but, if that fails to yield an improvement, I believe it will be a potential failure point when the car has it's first MOT next year.

[TonyHSD]

Hi, 

This corrosion is very typical for hybrids and electric cars due to the less intense use of the actual brakes, less friction and less heat.
There are  no manufacturer quality issues involved. If your Skoda was any sort of electrified, or even only mild hybrid or just a stop start power train with regen alternator it will be very similar results.
What we have in UK as additional to the regen braking is the salt on the roads during winter. This is the biggest issues we are facing every year. 
Corolla most models with large wheels and huge openings between spokes does not help against rain water too. 
I have seen most Toyota hybrids has corrosion on the rear brakes unless used daily, driven more spirited, or being garaged most of the time. Even new or recent cars plus those used and resold comes with horribly corroded discs, not only rear but fronts too. And btw, rear discs and pads are wearing faster than fronts and these are one of the first and only parts to get replaced on top of the regular service. 
 

[seetek]

On my year 20k main dealer service they told me that my rear brakes were wearing unevenly and got the nod off Toyota to change them.  I asked to see the old discs and they had score marks and pitting in them. They said they hadn't seen this before. Got new discs & pads though.

[Red_Corolla]

Thanks guys. I know the brakes on these don't get much of a workout, especially not in my case where the car does longer journeys but doesn't get driven every day (or even most days.) So I know it's always going to be a bugbear but just wanted to check how others fare because, as I said, my last car was genuinely one of a number built with cr@ppy discs. I don't have any specific issue apart from the corrosion - pad wear is even and material thickness still very similar to brand new pads after only 15k.

[AisinW]

IF you still have warranty, the brake disc is actually covered by standard warranty and Relax-warranty.  I don't buy Relax-warranty scheme so I go aftermarket disc.  The OEM brake disc are not that great because they are only partialy painted.  We can buy non Chinese made brake disc such as Zimmermann (made in Germany) and it is fully coated with Zn polymer.  What happened on OEM disc, the rust creep up under the thin pads materials layer etched to the disc. So, it rusted from inside. Or it just have some patchy area that has not enough contact and build up rust that never get cleaned up and hardened.  I have this problem on front disc instead.  

[TonyHSD]

Guys, 

you show not worry about your brake discs, as long as they are not made in India you will have no issues because of them. 👍

 

[AndrueC]

Mine are always corroded. It's because I hardly ever use them. I take the view that brakes are for stopping and for correcting mistakes.

I got dinged on my last MoT apparently because of it. The moral of the story being to do a couple of hard stops before the next MoT.

[TonyHSD]

The few hard stops will not clean the discs  but will scratch them badly and the MOT tester will note that on the certificate as advisory or simply fail the car. Will be rear brakes imbalance and rear brake discs severely scored and corroded. Regular moderate use of the brakes and few long progressive braking from 60-20mph will polish them better but all that if slider pins aren’t stuck pistons move freely. Lack of use and water plus salt aren’t doing any good to car brakes. 

[AisinW]

I don't think India 3rd grade manufacturing will get ECE-R90 certification. 

If we live in wet and regularly salted roads, coated brake disc is a must. I think Hella Pagid, Ferrodo, Zimmerman, Textar, and ATE offer Zn Polymer coated disc. But I heard ATE disc is not that good for Auris2, it wrapped easily. Zimmermann is really good but not the cheapest.

The original OEM disc is not even painted, very poorly protected from salts. Check the inner parts of the disc, they often corroded way more badly the outer side. 

[Jayel]

I have been looking at this subject with interest. I have got a 2020 70 plate Corolla 2.0 Design hatchback, which has recently had its 4yr/40k service. Being retired my mileage is below average (21k) and the car may go several days without being used.

The dealer has flagged up corroded rear discs which I am having replaced at a cost of over £300. My previous car, an Avensis had similar use and never had any of this nonsense. I have to assume therefore that it is down to the regenerative braking as I rarely feel the brakes actually "bite".

I will get the job done this time and judging by what others have said will do some occasional spirited braking in the future. I'm a bit miffed about it as it has spoilt what otherwise been a very economical car.

 

[sportse]

My Corolla isn’t doing too bad so far with the rear brakes. The rust all round after washing gets wiped off after half a mile of normal driving - maybe just braking a bit firmer when coming to stops and holding the brakes until you are almost stopped. 
 

on my auris it wasn’t very good, I regularly had to put the car in neutral every week or two and brake to clean up the rears. Otherwise I’d get a grinding noise when coming to a stop. The rear discs were worn out by 60k miles and had to be replaced. 

[Red_Corolla]

So, shortly after starting this thread last year, I removed my rear brakes and cleaned the hard,scaly corrosion from the discs, then gave the pads a light sanding to try and reset the bedding process. It was partially successful - there is still corrosion, but the heaviest of it is now isolated to around the circumference and most of the swept area is clean enough. They are better than they were throughout the first couple of years, and I think they will survive the first MOT without an advisory.

[TonyHSD]

Well done Stuart. 
The problem with Toyota hybrids and evs brakes is that they are operating cold most of the time. Water finds its way into the slider pins , those gets rusted and become stuck, which makes the callipers works one side only. 
With the time the discs gets corrosion from rain and moisture in the air , but the brake pads does not clamp hard enough to clean it. 
Many owners believe that discs and pads aren’t as good as on older cars., no , they are good but they work under different conditions. 
Regular brake service, especially on those low miles cars is the most. 
My neighbour has Corolla 71 reg on low miles and her rear  discs looked really bad. I noted recently she got new discs, something that could have been avoided with brake clean and lube service. 

[Red_Corolla]

@TonyHSD periodic inspection & cleaning is a big help, for sure, and one of those areas where we can attain a higher standard as DIYers compared to a pro garage, who would normally only do visual inspection until there's either an issue or something reaches the end of it's service life.

Something I've come to realise over the years is the initial days and weeks of driving when the brakes are new are critical for the condition of the discs, particulary in cold seasons: It's important to generate some wear & tear, as there is a sort of race between the bedding-in process completing and corrosion setting in. If you let the latter win then they never properly bed and you end up with rings of rust that never clear up. Contrary to the traditional and safety-conscious advice to take it easy during this period, I think the best thing for the components themselves is actually to do some HEAVY braking where circumstances safely allow it.