Rav 4 Brake Discs

[North Pole]

Hi - I haven't been on here for ages.

I have a 30mth old Rav 4 purchased from new. After 15mths the front discs were severely pitted by corrosion and the dealer skimmed them despite being asked to replace them. Now they are corroded again and the dealer says that the manufacturers warranty doesn't cover wear & tear. Aslo the car has a very low mileage, 17K, so that also contributed to the problem. The car is used every day allbeit maybe only for 4/5 miles sometimes. The rear discs are fine. I maintain the problem is due to poor quality metal in this instance. A previous Rav we had for 3 years dindnt have any such problems. The reversing warning signal aslo packed in.

Any opinions or advice would be appreciated especially if this is a known problem.

Cheers

[Big Kev]

Hi NP and welcome back to the fooled....sorry...fold. The following is my opinion only, formed over the past year of having a similar problem to you. First of all, you are passing wind in a hailstorm...Toyota will dig in to their "18k miles or 2 years" warranty crap until a pink moon rises, so sort this yourself.....18k miles warranty, I repeat...mince.

Are your brake discs pitted with corrosion, or are they covered in "rubbed off" brake PAD material?

If the former, I don't know what you would do, considering they have already been skimmed....if the latter, change the pads to some non Toyota ones like what which I did, and my discs are cleaning up a treat, and brakes have improved into the bargain....not dramatically, except in the wet (....Glasgow) when the difference is well noticeable.

One regular contributor reports no rub-off from his replacement TOYOTA pads, discs skimmed at 41k and pads replaced....

Hope this is of some help, and written in the certain knowledge that if I am wrong, there will be somebody along soon to correctify.

Big Kev

[North Pole]

Hi Big Kev

I appreciate your reply.

I know I'm 'farting against the wind' against Toyota but I thought I'd get some back-round info before I confront them.

The discs have pitted with corrosion again and I'm convinced that the ones I've got are of sub-standard manufacture. So if anyone knows of similar problems I be interested to know.

[Davrav]

Hi Big Kev

I appreciate your reply.

I know I'm 'farting against the wind' against Toyota but I thought I'd get some back-round info before I confront them.

The discs have pitted with corrosion again and I'm convinced that the ones I've got are of sub-standard manufacture. So if anyone knows of similar problems I be interested to know.

Anchorman is the expert here on brakes [and a great deal else too] and I'm sure he will confirm that it is extremely unlikely to be sub-standard manufacture. The discs are simply grey cast iron.

As Kev has said, the corrosion is caused by depositing of pad material onto the disc surface rather than abraiding them clean. Ergo, in my opinion, if you were to persue Toyota with regard to sub-standard parts you might be better to challenge the 'fitness for purpose' of the pads.

There have been many of us unhappy with the poor performance/Toyota's stance. One owner defected to another manufacturer because of Toyota's intransigence [is that how you spell it ]

If the corrosion is not too bad and not affecting braking you could, as Kev suggested, change the pads for a more abrasive brand and let them clean up the discs.

I am the member Kev mentioned and, since I recently had discs skimmed and new pads fitted by Toyota [at my expense ] the front dics have remained clean. I am pretty much convinced that the new pads are a different compound though my dealer would/could not confirm.

If you are not experiencing any judder, why not roll by your nearest MOT centre for an opinion and, if the discs are deemed Ok to pass, fit an aftermarket set of more abrasive pads. I'm sure Big Kev would let you in on what he now has fitted if you speak nicely to him

[anchorman]

Hmmm, well. It all depends on what you are complaining about. If it is just wear and pitting then I'm afraid you are wasting your time. It seemed at one time that whoever you talked to about having their car serviced had been advised that they needed a disc scim with new pads or new pads and new discs. I get the feeling that TGB got rather sick of these warranty claims and placed their own limits on the warranty for such conditions.

The fact is that regardless of how they look, unless you can demonstrate that they are failing to work as they should in terms of plain performance or any safety related like pull, judder etc, then you have no claim. Your exhaust might look rusty but if it works they won't change that either. Probably not what you want to hear but I'm afraid that is how they view it.

However, without putting words in your mouth, if you can demonstrate some sort of performance issue then you do have a claim Have you tried braking quite firmly on a quiet dual carraigeway to see if they judder? A lot do

[bothwell_buyer]

I'd guess that outside of ancs' knowledge, I have tried more types of disc on my RAV than most - EBC/ Toyota/ Rotordisc/ and a handful of others.

Basically they are all much the same manufactured from much the same - steel is steel. The difference lies in the pad compound..... and then how you drive; how hard the brakes get used and the way they get used.

Discs will rust as soon as you have stopped driving on that same day. You can now buy discs which resist rusting, but then you pay the price.

If you are doing a fairly low mileage - actually I only do about 6000 miles a year in each of the RAVs I have - then rust will build up. However I don't have a great problem with disc rust as I use number 1 RAV for sprint type racing and very fast road work, and the brakes get used very heavily from 100+mph down to 10mph ... much like emergency braking. On number 2 RAV, also fitted with a turbo engine and a fast car, I do fast road driving and heavy braking - it ensures that the brake components are all getting a chance to warm up to working temp and everything is working at 100%. Number 2 is using Toyota discs and pads.

So, its worth giving the car a fast run and braking job to clean the discs and keep all working well. Do not hold the footbrake down after a fast braking session as the pads will melt onto the disc causing the 'warped disc' syndrome. Use the handbrake.

[North Pole]

Thanks for all your comments - I'm glad I posted to get your perspectives on this.

I found the technical advice useful so I took the wheel off tonight for a proper look and took a sander to the discs. After the rust was removed the surface didn't look as badly pitted as I thought. (On the first occasion they were 2 -3 mm deep over 75% of the surface) I can put up with this but will change the pads as recommended and will keep a close eye on the discs.

The performance is not affected so I wont make a nuisance of myself.

PS The wife normally drives this car and I make do with a banger!!!

[anchorman]

If any local stockists keep apec, give them a try. They are slightly abrasive and will really clean up the disc.

[Big Kev]

I'd guess that outside of ancs' knowledge, I have tried more types of disc on my RAV than most - EBC/ Toyota/ Rotordisc/ and a handful of others.

Basically they are all much the same manufactured from much the same - steel is steel. The difference lies in the pad compound..... and then how you drive; how hard the brakes get used and the way they get used.

Discs will rust as soon as you have stopped driving on that same day. You can now buy discs which resist rusting, but then you pay the price.

If you are doing a fairly low mileage - actually I only do about 6000 miles a year in each of the RAVs I have - then rust will build up. However I don't have a great problem with disc rust as I use number 1 RAV for sprint type racing and very fast road work, and the brakes get used very heavily from 100+mph down to 10mph ... much like emergency braking. On number 2 RAV, also fitted with a turbo engine and a fast car, I do fast road driving and heavy braking - it ensures that the brake components are all getting a chance to warm up to working temp and everything is working at 100%. Number 2 is using Toyota discs and pads.

So, its worth giving the car a fast run and braking job to clean the discs and keep all working well. Do not hold the footbrake down after a fast braking session as the pads will melt onto the disc causing the 'warped disc' syndrome. Use the handbrake.

You'll need tae stop this Bothy....coming on here and talking total sense....!!! Never thought of that one before, holding footbrake/pads on to hot discs. I shall desist immediately (bad practice anwayhowz.)

Big Kev

[crofter]

I'd guess that outside of ancs' knowledge, I have tried more types of disc on my RAV than most - EBC/ Toyota/ Rotordisc/ and a handful of others.

Basically they are all much the same manufactured from much the same - steel is steel. The difference lies in the pad compound..... and then how you drive; how hard the brakes get used and the way they get used.

Discs will rust as soon as you have stopped driving on that same day. You can now buy discs which resist rusting, but then you pay the price.

If you are doing a fairly low mileage - actually I only do about 6000 miles a year in each of the RAVs I have - then rust will build up. However I don't have a great problem with disc rust as I use number 1 RAV for sprint type racing and very fast road work, and the brakes get used very heavily from 100+mph down to 10mph ... much like emergency braking. On number 2 RAV, also fitted with a turbo engine and a fast car, I do fast road driving and heavy braking - it ensures that the brake components are all getting a chance to warm up to working temp and everything is working at 100%. Number 2 is using Toyota discs and pads.

So, its worth giving the car a fast run and braking job to clean the discs and keep all working well. Do not hold the footbrake down after a fast braking session as the pads will melt onto the disc causing the 'warped disc' syndrome. Use the handbrake.

You'll need tae stop this Bothy....coming on here and talking total sense....!!! Never thought of that one before, holding footbrake/pads on to hot discs. I shall desist immediately (bad practice anwayhowz.)

Big Kev

Strictly non techie comment.

Don't know if this still applies today.

Learning to drive (NO! it was post steam driven)one bit of advice was to always apply the handbrake when stopped in case you were rammed up the jacksie as your foot would be lifted off the peddle and the vehicle would react like the steel balls that hang on desk toys.

As the truck I was being taught on had a flat front,so not much between you and possibly the back end of loaded lorry,I suppose it had its merits.

Del.

[El Bee]

So, its worth giving the car a fast run and braking job to clean the discs and keep all working well. Do not hold the footbrake down after a fast braking session as the pads will melt onto the disc causing the 'warped disc' syndrome. Use the handbrake.

That's pretty much the size of it except that discs are cast iron rather than steel, they can be made not to rust but then some of the required friction goes AWOL. Not really a desirable situation as it's needed to transform the kinetic energy of the vehicles forward motion into heat - 1st Law of Thermodynamics refers.. And there's a virtual pint on offer for anybody who can quote the 0th Law of Thermodynamics without looking it up

In an ideal world you should start with a new or resurfaced set of discs and subject them to half a dozen hard brake applications to condition the disc and get a smear of pad material onto them, too often the brakes are used lightly and pad material can build up causing the "warped disc" feel which is felt by the driver even though it is less than a fifth of a millimetre thick. Those high spots cause further vitrification and the whole thing snowballs.

DO check suitability of pads carefully though, some,which are effective at low temperatures are made of materials which decompose unevenly at higher temperatures causing more problems.

I have been known to use a metal sanding disk with diamond dust on it (I think intended for shaping ceramic floor tiles) to remove the glaze and grooves on brake discs prior to changing pads [1] but this is probably an Elf & Stacey infringement so I couldn't commend it to the house.

Lee

[1] A bit like honing a bore before fitting new rings.

[anchorman]

Good heavens.

[Big Kev]

Always an interesting and informative read from these Marine Engineer folks, usually bred from their experiences of being hunnerz of miles out at sea, and guess what....? There's no B & Q Superstore oot there.....ye need to fix it with what you've got.

Just an observationment...

Big Kev

[El Bee]

Always an interesting and informative read from these Marine Engineer folks, usually bred from their experiences of being hunnerz of miles out at sea, and guess what....? There's no B & Q Superstore oot there.....ye need to fix it with what you've got.

Just an observationment...

Big Kev

I knew I had it roughly right but memory being what it is I just did a bit of research and

"Once the disc has some level of variation in thickness, uneven pad deposition can accelerate, sometimes resulting in changes to the crystal structure of the metal that composes the disc in extreme situations. As the brakes are applied, the pads slide over the varying disc surface. As the pads pass by the thicker section of the disc, they are forced outwards. The foot of the driver applied to the brake pedal naturally resists this change, and thus more force is applied to the pads. The result is that the thicker sections see higher levels of stress. This causes an uneven heating of the surface of the disc, which causes two major issues. As the brake disc heats unevenly it also expands unevenly. The thicker sections of the disc expand more than the thinner sections due to seeing more heat, and thus the difference in thickness is magnified. Also, the uneven distribution of heat results in further uneven transfer of pad material. The result is that the thicker-hotter sections receive even more pad material than the thinner-cooler sections, contributing to a further increase in the variation in the disc's thickness. In extreme situations, this uneven heating can actually cause the crystal structure of the disc material to change. When the hotter sections of the discs reach extremely high temperatures(1200-1300 degrees Fahrenheit), the carbon within the cast iron of the disc will react with the iron molecules to form a carbide known as cementite. This iron carbide is very different from the cast iron the rest of the disc is composed of. It is extremely hard, very brittle, and does not absorb heat well. After cementite is formed, the integrity of the disc is compromised. Even if the disc surface is machined, the cementite within the disc will not wear or absorb heat at the same rate as the cast iron surrounding it, causing the uneven thickness and uneven heating characteristics of the disc to return."

So there

Lee

[Big Kev]

Cheers Lee....ah will print this out, and take it t'pub and recite it verbatim. When they are all sleeping, ah will steal their drinks. Cheap night oot here I come...!!!!

Big Bevvy

[anchorman]

It sounds american to me.

[Davrav]

It sounds american to me.

Really? I thought you wrote it - sure I could detect a Derbyshire accent in there somewhere

[El Bee]

Cheers Lee....ah will print this out, and take it t'pub and recite it verbatim. When they are all sleeping, ah will steal their drinks. Cheap night oot here I come...!!!! Big Bevvy

Now that's what I call lateral, or should it be horizontal, thinking Kev, you can always trust a Scot to sniff out free beer

As Anchs sez, it sounds a bit 'murrican, the chemistry is about right though...

And if you think that one is boring I'll look out the paper (about 400 A4 pages) on the effects on bearing wear when a crankshaft on a Burmeister & Wain low speed marine diesel is out of balance, you'd chew yer own arms off with boredom :(

Anyway, as a special treat, have you seen this one....

Has car content and an excitable lady :)

Lee

[Big Kev]

We would call the company "Burmeister and Son" up here Lee, but at least now I know what BMW ACTUALLY STANDS FOR....

Big Kev

[El Bee]

We would call the company "Burmeister and Son" up here Lee, but at least now I know what BMW ACTUALLY STANDS FOR....

Big Kev

<groan> It's good that all Jock Kids are called Wayne, saves confusion all round, dead right what Billy Connelly sez they don't know which one belongs to who(m) so I guess sharing them out, by number works

And Burmeister & Wain engines are generally referred to as "B&Ws" so I see where y're comin' frae, lovely engines to watch though, pushrod/rocker/valve setup, the rockers are about 6 feet long and best part of ¼ ton each, the 'rod comes up about a foot, depressing the valve and a spring as big as a 45 gallon oil drum a similar amount, valve clearances are set at the handle thickness of a 12" Bahco shifting spanner - it's all a bit like wandering around inside a well lit rocker box

They go through a lovely phase on acceleration, probably the 60 to 80 rpm range where the turbo blowers are really coming on song and the valve gear is settling into its lovely clatter and the plates beneath your feet settle into that "we're off" rhythm - pure magic....

Lee