Rear brakes corroded

[rutherford]

Just had my rear pads and discs replaced on my 17 reg yaris hybrid after 4000 miles. One side was grooved..both sides exhibiting rusty dust lying on the alloys. Edges of discs rusty. I expect to see black dust from the pads but not metal from the discs...what is going on.

[FROSTYBALLS]

Please update your profile to include the Yaris.

Moved to the Yaris club

[Heidfirst]

my guess:

As I am sure that you know discs gather surface rust even overnight if the conditions are damp. In a normal car with normal usage this is quickly cleaned off by the pads. However, hybrids use regenerative braking so if you have only light usage (you don't say how long you have had the car, but only 4000 miles) & are light on the brakes anyway then the pads may not get used enough to clean the discs fully & over time the corrosion will build up further which can then lead to scoring.

I think that if you search you will find posts on various forums where people experienced increased corrosion on the discs of hybrid vehicles.

[monkeydave]

i had my rear discs do that on my jazz, they dont get enough pressure on short runs without heavy breaking, the dealer tried to get me to replace them each year for 3 years from the second service onwards, i traded the car before i replaced them as they still passed the mot and i knew the new ones would go rusty on the outer edge just the same

 

that is the one thing that is good about drum brakes on the rear, you can park the car for days and days in the rain and they never stick on when you drive off

[rutherford]

Thanks for the explanations.  Another odd thing was the rear brakes appeared to have locked on when the car was standing overnight. Handbrake was released, when the car moved a bang was heard which I believe was the pads releasing. Rusty dust..scoring..rust on disc edge..none of these apply to the front discs. Just the backs. 

[Heidfirst]

your handbrake only operates on the rear brakes so the rear pads are in contact with the discs overnight but not so fronts. That will promote rusting.

When in motion the bulk ( iirc ~ 2/3) of the braking on a normal car is done by the front brakes so they will clean the discs better than the rear. I am not sure how that translates to usage on a hybrid with regenerative braking but no doubt someone who does will be along to illuminate us.

[rutherford]

Many thanks for all the replies and associated information. Toyota changed the pads and discs today without any quibble so if they need changing again  in 6 months then so be it.

[bathtub tom]

The first car I had with rear discs taught me to give the brakes a regular, heavy application every journey (keep an eye on the mirror). I did have to replace all the pads around 40K, but never the discs.

[stantheman1]

21 hours ago, rutherford said:

Thanks for the explanations.  Another odd thing was the rear brakes appeared to have locked on when the car was standing overnight. Handbrake was released, when the car moved a bang was heard which I believe was the pads releasing. Rusty dust..scoring..rust on disc edge..none of these apply to the front discs. Just the backs. 

Sounds to me like you'd washed the car the day/night before and left it stood overnight without taking out for a 'spin'. I too learned the hard way, now every time I wash the car I take it on a short journey and occasionally  pull the hand brake on a notch or two for a few seconds at a time, that way guarantees the rear brakes gets plenty of use which dries them off. Or you could find a steep hill to drive down.

.....Or it could be due to all that wind and rain we've had recently being driven into the side of the car.

[rutherford]

Hello  I never wash my cars myself  always use a local car wash  for £3 it is not worth my time and I am on a water meter at home. Therefore the car always have a spin before parking on the drive

 From the thickness of the rust on the edge of the disc I am convinced the metal is not good. Hopefully these new toyota supplied discs are better quality. Had a call from the garage today asking if I was happy about the service received. I pointed out that I thought disc pad material was softer than the steel disc to which I got agreement. So then why I asked was the disc scored after 4000 miles. 

[rutherford]

Must point out that the edges of the front discs are not contaminated with thick red rust which sort of discounts the washing theory and the weather theory. Also the dust from the disc brakes on the front is black as you would expect whilst the back alloys were covered in red rusty dust from the brakes.

[stantheman1]

9 minutes ago, rutherford said:

Hello  I never wash my cars myself  always use a local car wash  for £3 it is not worth my time and I am on a water meter at home. Therefore the car always have a spin before parking on the drive

 From the thickness of the rust on the edge of the disc I am convinced the metal is not good. Hopefully these new toyota supplied discs are better quality. Had a call from the garage today asking if I was happy about the service received. I pointed out that I thought disc pad material was softer than the steel disc to which I got agreement. So then why I asked was the disc scored after 4000 miles. 

I was referring to the 'bang' when the car is first moved, anyhow it could still be all that wind and rain or does it happen every time you've been parked up for a while regardless of the weather?

Also be aware that these cheap car wash establishments use extremely harsh traffic film remover chemicals such as 'hazsafe' etc  especially on the wheels and lower body panels and any exposed metalwork is prone to rust afterwards, i've seen this many times, take a look next time you see a car with plastic wheel trims that frequent these premises, a lot of the steel wheels are rusty under the trims and compare to those that wash their cars at home. Just saying!

[Madasafish]

The "bang" is normal for almost all rear disks used for a parking brake. It can be exacerbated if all the brake mating surfaces where the pads move or swivel are corroded and have never been greased. What then happens is part of the pad moves and part does not so you get brake disk scoring= as you had.  The solution is regular brake maintenance yearly. NO maker of small cars has that on the maintenance schedule.

 

Winter road salting makes it worse- do you live near the sea? As salt spray is highly corrosive.

[Cyker]

Is rust on the disc surface that big a deal? I always feel they make the brakes feel *better* for that magical moment the day after I've washed my car and the discs have that patina of rust! The grinding sound isn't so nice tho'...

It's normal for the edges of standard discs to get super rusty over time - They're made of iron, which will just start slowly rusting from the moisture in the air - And unlike the face, they never get abraded by brake pads or anything so they are always rusting.

If it really bugs you, you can get ones with coatings that stop them rusting up so much; Supposedly EBC do ones with an anti-corrosion coating on them so you don't have to degrease them and that keeps the hub and edge much cleaner over its life. (I've only ever gotten regular iron ones from them so you may need to ask for them specifically?)

[Heidfirst]

19 minutes ago, Cyker said:

Is rust on the disc surface that big a deal?

Imo, thin surface rust, no. If it is allowed to build up to the extent that it actually starts eating into the braking surface then yes. In a normal car that wouldn't happen unless it was unused for months but anecdotally at least hybrids with regen braking do seem to suffer more because they use far less friction braking & therefore often don't clean the surface as well.

If it really bugs you, you can get ones with coatings that stop them rusting up so much; Supposedly EBC do ones with an anti-corrosion coating on them so you don't have to degrease them and that keeps the hub and edge much cleaner over its life. (I've only ever gotten regular iron ones from them so you may need to ask for them specifically?)

I had this (it's really just high temp paint or similar imo) on the MTEC discs that I fitted to my Avensis T25. It certainly kept the hubs & edges better looking.

 

[bathtub tom]

Many years ago on a visit to Aston Martin in Olney, there was guy painting the outside edge of the discs.

[rutherford]

Hello  this car is 9 months old has 4000 on the clock. The rear discs and pads have been changed by toyota at no cost to me. The front discs are smooth and have minimal sign of rust on the edge. The rear ones were a different story..really heavy red rust on the edge..discs scored...do not forget only 4000 on clock. Also the rear alloys were covered in fine red dust unlike the fronts which have black dust which I expect to see. Regenerative braking..car wash..overnight parking..all good ..but..I am convinced that toyota are supplying new cars with inferior parts on the brakes. No quibble exchange and no reason given indicates to me that they know all about this problem. If 2/3 of the braking power is on the front I would expect these to be scored....if only 1/3 is on the back yet discs heavily scored

 

[Cyker]

Nah mate you got it backwards - The fronts will be smoother because the pads are being used more there; Effectively cleaning and polishing them every time you brake. The backs are scored because the pads don't grip them as much so they don't get as hard a polishing, letting rust and crap build up on them until next time you brake harder when then scrapes off a layer.
This is very common most cars with a 60:40 brake force distribution and rear discs. Even my dad's Verso has noticeably shinier discs on the front than the rear.

The reason the dust is a different colour is the black dust is pad dust, while the red dust is due to rust from the disc being ground off by the pad. It's not because of material differences.

I don't really understand some of the decisions they made for the HSDs - They use bigger rims than are standard for any of the petrol versions, which make the mpg worse despite them pitching the car for high fuel efficiency and use rear discs where rear drums would be more than adequate...!

[Heidfirst]

8 minutes ago, Cyker said:

I don't really understand some of the decisions they made for the HSDs - They use bigger rims than are standard for any of the petrol versions, which make the mpg worse despite them pitching the car for high fuel efficiency and use rear discs where rear drums would be more than adequate...!

the bigger rims in the UK is an UK marketing decision - the UK has a perverse relationship with large wheels & low profile tyres (I'll admit that they look better but they are more expensive, are more prone to damage & wear faster).

I have a suspicion that regenerative braking may not work as well with drums.

[Cyker]

Oh, is it? I thought it was a global thing. Can you buy a Yaris HSD anywhere with e.g. 14" or 15" rims as standard??

I much prefer the smallest rims I can get - The ride is much comfier and tyres are waaay cheaper. The tyres for the Mk2 I now have are £20-30 more expensive than the equivalent ones for my old Yaris - nearly double! - and that's just going from 175/65R14 to 185/60R15!

Annoyingly, if I changed to 14" rims, even if they were steel, it would be classed as a change from OE by my insurer and they'd add a charge for modification onto it... Boooo...

[Heidfirst]

25 minutes ago, Cyker said:

Oh, is it? I thought it was a global thing. Can you buy a Yaris HSD anywhere with e.g. 14" or 15" rims as standard??

In Europe (don't know which exact countries but it does include the UK if you check toyota.co.uk) you can get a Yaris HSD with 15" steel or alloy wheels according to grade (if you are buying a top. spec. you will get 16" alloys). https://www.toyota-europe.com/configure/yaris#carconfig/engine_grades/09a6531a-c3f1-4d2d-b4d3-eb45cbb35478

It doesn't look like 14" wheels are an oem fit for any new Yaris.

[Cyker]

Oh yeah, you're right, it was indeed just the top-spec that forced you to have 16" rims!

[Mike J.]

My Yaris Hybrid manual notes 7 valid types of wheels and tyres. Three of them are 14 inch (175/65 and 175/70 are quoted tyre sizes). It should be possible to negotiate such a change with your insurers for free - I have .... To keep the proper rolling radius, the 70 profile is probably best if you have 195/50x16 at the moment. eBay have cheapish 14" steel rims, good for winter tyre use.

[Cyker]

Yeah, the manuals usually list things like oil and rim/tyre size for every variant in the range, but that isn't the same as what is considered standard equipment for the car, which is the important thing when it comes to insurance!

Some insurance companies are a bit more lenient than others, but I find the majority will take any deviation from stock as a modification even if it's something stupid like moving to smaller rims or changing from alloys to steels!

[FROSTYBALLS]

As far as I'm aware, the 14 inch wheels were available on non-hybrid models - probably the 1.0 litre petrols.

Some insurance companies are more lenient than others - there is a post on the one topic in the Toyota Insurance Discussions where Toyota Insurance refused to accept 15 inch winter wheels/tyres on an Auris because they weren't part of the standard spec for the insured's car (which had 17's as standard).