Front Disc Wear

[christine rooks]

We've just had the front pads and discs replaced by Toyota service garage. Car is 5 years old and has done 34,800 miles. Old discs were clean (ie no grooving) and compared to new ones fitted the old discs had worn by 0.025in (0.63mm) each side. Has the garage stung us, what is the allowable wear on a disc?

[bitman]

you don't write the year of your rav 4.

on a 2001 model min is 23mm thick.

[christine rooks]

you don't write the year of your rav 4.

on a 2001 model min is 23mm thick.

Its a 2003 model and the measured thicknes is .933in(23.6mm) so I guess they say it would be below this by next service. Thanks

[Parts-King]

The discs may not have looked worn, but there are two things to look for when changing pads. Firstly, if there was any juddering under braking?, this may indicate the disc is warped or has "runout" the max runout on your car is only 0.05mm or 0.0020 Inches. The second thing is minimum thickness, the disc must be replaced if the min thickness anywhere on the disc is below 23.00mm 0.906 inches. A warped disc can be cured by skimming, but if it is below the min thickness, they must be replaced

Kingo

[bothwell_buyer]

Ok - here we go - an old chestnut that grinds with me!!!

I'm sorry you've probably been stung.

The minimum or discard thickness of the disc is normally cast into the inside of the 'bell' of the disc. Toyota discs vary in thickness depending on the age of the model you have.

In days of old, a garage would send a disc away to be skimmed if there was excessive scoring on the disc face. Too many garages now just tell you that new discs are needed.

the remaining thickness of the disc is really only measured properly using a micrometer, as there will be a lip on the outside surface of the disc where the pad hasn't touched = normal.

In an MOT the car brakes will be failed if the tester judges that the disc is too scored - discs get scored cos of pads being run down too far, or grit etc getting in between pad and disc face. Minimal scoring is normal and expected.

I have had innumerable sets of discs replaced on my 1994 RAV - so much so that I have had custom ones made by KAD, together with the front calipers.

Back to the subject in question - if your disc is not scored, and you have only done 34,000 miles then my opinion would be that your discs are fine. Your pads might need replaced if not done already, but not the disc. The Toyota disc of 1994 was, in my opinion, a poor quality disc not fit for purpose. It was 18mm, so I guess your car is a fair bit younger. However, some Toyota dealers have milked the gullibility of customers by saying you need new discs. I got it on authority of 1 Toyota dealer mechanic that they charged for discs even if they weren't fitted!!

So, ask for the 2 old discs back and take them to a different dealer for an opinion. You could even try asking a tester at an MOT station for his/her opinion as they will be clued up on brake safety. If you have access to a micrometer you can measure the thickness yourself and compare it to the minimum allowed. If the opinion is that the discs are fine, lets hope you paid by credit card as you can ask for your payment back.

Then speak to trading standards as they will be interested - trading standards will have local officers that you should meet - up here they have a call centre off the West coast - so make sure you meet the TS folk. If folk don't speak up, this practice will continue.

In my humble opinion, the wear mentioned is well within safe wear.

In saying all of that, discs will wear at different rates - the surface develops rust within a day so if the car is sitting for any time then the pad will remove the surface rust when driving and more wear may result. I'd have guessed disc replacement at 60k miles or thereabouts.

[anchorman]

I tend to agree with bothy. I think you may have been stung but the trouble is the assessment of discs is very subjective. The wear of the disc should always be measured with a ball end micrometer 25mm in from the edge. This is the point of maximum wear because firstly the outside of the disc has a higher rotational speed (and it will always wear coned shape like a clutch does) and also the disc rocks about the centre line of the axle or stub due to a small amount of play in the bearings. The latter causes some "off brake" contact with the pad. You will probably find that the disc wears back to this level in much less than 35k but will then stabilise to a much lower rate of wear.

Now as to taking issue with them I think it is probably a bit late. I would always recommend that when leaving a car with the dealer that the owner stipulates that no work should be done without authorisation. Also if you follow the recommendation of the pad manufacturer (who coincidentally usually sell discs) that they always recommend that if the disc shows any signs of wear that they are re-skimmed or replaced - and as I said that assessment is subjective. In practical terms you have been screwed but as far as the law goes I think you might have to take it on the chin.

On a positive note the pad material that Toyota uses is absolutely first class and well worth the money.

Welcome to the club Christine.

PS Bothy is available for hire. He can be astonishingly effective when negotiating with dealers. He only accepts cash, alcohol or certain types of bric-a-brac (Land Rover parts).

[christine rooks]

Ok - here we go - an old chestnut that grinds with me!!!

I'm sorry you've probably been stung.

The minimum or discard thickness of the disc is normally cast into the inside of the 'bell' of the disc. Toyota discs vary in thickness depending on the age of the model you have.

In days of old, a garage would send a disc away to be skimmed if there was excessive scoring on the disc face. Too many garages now just tell you that new discs are needed.

the remaining thickness of the disc is really only measured properly using a micrometer, as there will be a lip on the outside surface of the disc where the pad hasn't touched = normal.

In an MOT the car brakes will be failed if the tester judges that the disc is too scored - discs get scored cos of pads being run down too far, or grit etc getting in between pad and disc face. Minimal scoring is normal and expected.

I have had innumerable sets of discs replaced on my 1994 RAV - so much so that I have had custom ones made by KAD, together with the front calipers.

Back to the subject in question - if your disc is not scored, and you have only done 34,000 miles then my opinion would be that your discs are fine. Your pads might need replaced if not done already, but not the disc. The Toyota disc of 1994 was, in my opinion, a poor quality disc not fit for purpose. It was 18mm, so I guess your car is a fair bit younger. However, some Toyota dealers have milked the gullibility of customers by saying you need new discs. I got it on authority of 1 Toyota dealer mechanic that they charged for discs even if they weren't fitted!!

So, ask for the 2 old discs back and take them to a different dealer for an opinion. You could even try asking a tester at an MOT station for his/her opinion as they will be clued up on brake safety. If you have access to a micrometer you can measure the thickness yourself and compare it to the minimum allowed. If the opinion is that the discs are fine, lets hope you paid by credit card as you can ask for your payment back.

Then speak to trading standards as they will be interested - trading standards will have local officers that you should meet - up here they have a call centre off the West coast - so make sure you meet the TS folk. If folk don't speak up, this practice will continue.

In my humble opinion, the wear mentioned is well within safe wear.

In saying all of that, discs will wear at different rates - the surface develops rust within a day so if the car is sitting for any time then the pad will remove the surface rust when driving and more wear may result. I'd have guessed disc replacement at 60k miles or thereabouts.

[christine rooks]

Thanks bothwell. We have now shown the discs to an MOT tester at an independent non-franchise garage and he found no problem with the discs, they were evenly worn with the outside lip you mentioned. He said if it was his he would have just ground off the lip, but if it had come in to their test station they probably would have put in an adisory to have pads and discs changed before next MOT ie in 12 months time. In answer to anchorman, the thicknes was micromter measured approx 25mm in and the thickness was 23.6mm "against the 23mm minimum recommended. So will now confront garage again.

[Hoovie]

Hi Christine, welcome to TOC and the best section in it

Playing devils advocate a bit here ...... Looking at your Mileage for the age of car, if the discs and pads were changed on your annual service, they may have said they need doing now, as if you left them until the next service they would be too low (based on the comment from the MOT guy you spoke to).

Many garages seem to take the approach of dealing with things in the service that MAY have gone past their useful/recommended life by the time the next service is due, rather then saying to the customer "come back in 3 or 6 months" or whatever.

FWIW, my mileage is 28,000 on a 2005 RAV and the garage suggested skimming the discs in the last service just a month ago (in this case, they skimmed and replaced pads FOC so I didn't really check any details on limits)

[Parts-King]

Christine

I'm sure this could have been handled a lot better by your garage, no doubt about that, but your measurement of 23.6mm makes the disc 0.6mm above its minimum. 0.6mm is a gnats breath!

Now that service intervals are every 12 months, we often find ourselves giving customers "advisory" notices that the discs "MAY" need replacing BEFORE the next service, its always a difficult balance, fit them now and be accused of being over cautious, or leave it 12 months and the discs are snookered. it's a fine balance, but one we try and explain up front

Kingo

[bothwell_buyer]

Christine

I'm sure this could have been handled a lot better by your garage, no doubt about that, but your measurement of 23.6mm makes the disc 0.6mm above its minimum. 0.6mm is a gnats breath!

Now that service intervals are every 12 months, we often find ourselves giving customers "advisory" notices that the discs "MAY" need replacing BEFORE the next service, its always a difficult balance, fit them now and be accused of being over cautious, or leave it 12 months and the discs are snookered. it's a fine balance, but one we try and explain up front

Kingo

Golly gosh - wot size of gnats dae ye have in Cheshire/North wales???

As per the discs, I'm sorry but i've got to say that in the good old days, when cars were cars and the landrover was unfortunately created, discs lasted much longer. The steel was often made in the UK (probably Scotland as we made the best steel) and lasted a long time.

Wait til Tatatata get hold of Jaguar and landrover and we'll see anchors being thrown out at passing lampposts!! Some folk'll say that cars travel faster now - aye well they do, but they are also on the whole lighter. Ah shuid know cos ah've tried shovin ma Humber hawk.

[shutty]

Discs were discs untill they took the asbestos out of pads. This means the pads are much harsher than before and disc wear is more common Current Corolla used to wear out in under 40k, Old Rav were poor and corroded badley

The dealer would have probabley chosen to skim but due to

A the cost of labour to skim comapred to new parts (book time was about 2.3hrs for a pair compared to just under an hour to replace V cost of new discs with a 12mth warranty

B - Skimming may and probably would have taken below min thickness

C - MOT test as little to do with it, Its a test on the day that states the brakes work effectively and have a minimum of 1mm of brake pad on them (Basically as long as it stops in a straight line they are ok)

D The thinner the disc and or pad the hotter they get, Brake fade isnt pleasent

I reported my dads discs for 2 services with the same reaction as most on here " Loads left there discs last for ages" before the day the osf disc shattered into 3 bits coming to a roundabout. The mad thing was he was happy safe in the knowledge he had used every last bit of wear out of them.

I agree in an ideal world it would be better to say come back in 6mths, would you remember ?, Would you bother ?

On the other hand - Fitting them is that easy i would do them myself but would replace at .6mm over min thickness

[bothwell_buyer]

Discs were discs untill they took the asbestos out of pads. This means the pads are much harsher than before and disc wear is more common Current Corolla used to wear out in under 40k, Old Rav were poor and corroded badley

The dealer would have probabley chosen to skim but due to

A the cost of labour to skim comapred to new parts (book time was about 2.3hrs for a pair compared to just under an hour to replace V cost of new discs with a 12mth warranty

B - Skimming may and probably would have taken below min thickness

C - MOT test as little to do with it, Its a test on the day that states the brakes work effectively and have a minimum of 1mm of brake pad on them (Basically as long as it stops in a straight line they are ok)

D The thinner the disc and or pad the hotter they get, Brake fade isnt pleasent

I reported my dads discs for 2 services with the same reaction as most on here " Loads left there discs last for ages" before the day the osf disc shattered into 3 bits coming to a roundabout. The mad thing was he was happy safe in the knowledge he had used every last bit of wear out of them.

I agree in an ideal world it would be better to say come back in 6mths, would you remember ?, Would you bother ?

On the other hand - Fitting them is that easy i would do them myself but would replace at .6mm over min thickness

I agree with wot yer saying but the truth is that the T discs are replaced too often at a gross price. I've bought too many sets to be other than wise. And of course, one has to buy sets in pairs!!

I know a thing or two about mechanics, and its makes no difference whether 1 disc has nil wear and 1 disc has fractional wear. You still have to but them in pairs cos they are made by the manufacturer in pairs. Rip off. i could start a shop selling nearside discs for RAV4 4.1s.

See what you say about asbestos, but theres a wide wide range of pads and pad material out there - softer pads = better grip = more frequent replacement....so whats cheaper - discs at £160 a pair+ ???

I took the dust shield off number 1 RAV front discs as a. it had corroded; and b. it served no useful purpose. Result - stones don't get trapped in between it and my calioers or disc, and I don't get any problem thrashing through water - but then I have 6 pot calipers fitted each side compared to the original 1 pot and sliding shoe. The only reason these aren't fitted from new is cost. So how come I paid £21600 for my RAV4 3 door in 1994 and now the price is even less 14 years later??? Where did the profit go then?? Sorry - I have no great regard for Toyota doing that; nor do I rate their brake discs.

As for coming back in 6 months - well I get call ups from the dentist every 3 months and the doctor gives me calls up too on a regular basis so whats the difference - I'm mad? Maybe, but which way?

[shutty]

Discs are supplied in ones

Half of what B&Q sell is less than 10yrs ago. Blame all the nutters that complained about Block exemption and importing cars into UK cos it was cheaper.

Build costs are less on all new vehicles like everything else in like its chepaly made cutting corners (TV's Cookers Car components its no different)

Discs have a 50% mark up - Down to dealer to discount for older vehicles

Nobody has mentioned how low the pads were ?

Please also remember Toyota have been learning the european market for the last 10years Pre VVTI, Climate changes compared to Japan, Hence why alloys rust, discs rust, Its a different driving habit in Europe and its taken time to understand

The biggest issue in cost for all dealers is Labour rate increase (Its gone up £25 in 2 years)

And the dealership business is the least profitable business going with a return on investment if your lucky at 1%, Most dont make a profit when the final numbers are counted

Sorry rant over

It gets to me when people whom know nothing about a scenario jump on the slate the dealer off band wagon when i used to see what independant garages do to cars and charge slightly less for doing it.

Where else would you get a 4x4 serviced at a manufacturer dealership for £150

See what Landrover charge for a Freelander service

[christine rooks]

Christine

I'm sure this could have been handled a lot better by your garage, no doubt about that, but your measurement of 23.6mm makes the disc 0.6mm above its minimum. 0.6mm is a gnats breath!

Now that service intervals are every 12 months, we often find ourselves giving customers "advisory" notices that the discs "MAY" need replacing BEFORE the next service, its always a difficult balance, fit them now and be accused of being over cautious, or leave it 12 months and the discs are snookered. it's a fine balance, but one we try and explain up front

Kingo

hardly a gnat's whisker, it has taken 5 year to wear 1.27mm!

[anchorman]

I was 17 years in brake development and testing for bothmeisters favourite pad manufacturer. I just thought it would be worth exploding a few myths about pads and discs;

Asbestos. It has some limited friction qualities and a good resistance to heat (it was often used as insulation) but its main property in terms of friction materials is that it disperses and bulks up when beaten. It creates what looks like candy floss and has no other purpose than privide a framework to hold the pad together. To this the other main categories are added -

Friction modifiers, usually abrasives in the form of zircon or silica sand. Sometimes lubricants like graphite or brass to stabilise friction under at different temperatures (friction that is too high or unstable is unnaceptable). Sometimes the friction modifiers are numerous and will be active at certain temperatures and dormant at others.

Fillers - These are inert substances like vermiculite and do nothing more than bulk the material up and resisit wear.

Binders - a thermo setting phenolic resin is used. It is added to the mix as powder and liquifies under heat. It is fully cured when the pads are finally baked.

Now to talk about asbestos substitutes. These are usually Rockwool (again common in insulation) and sometimes but rarely, Kevlar which has good properties but is around 40 times more expensive so is found more in body armour etc where the cost is not considered prohibitive. Both asbestos and rockwool are added at about 45% of the volume. The rest of the mix is essentially unchanged and when test it explodes 2 myths;

1. Asbestos is no less damaging to discs than rockwool.

2. If you actually test the hardness with a Rocwell hardness tester they are infact very similar and in some cases the asbestos free might be softer than the asbestos based.

So why do modern day discs and pads wear more than old asbestos ones I hear you say! Well lets talk about the one and only thing that makes pads wear out quickly (and it has absolutely nothing to do with friction and only marginally related to how abrasive the pads are). It is purely and simply down to heat. What has changed significantly over the last 20 years or so - coincidentally about the same time as asbestos was withdrawn, are the demands on the braking system. Legislation and safety requirements have mushroomed and the net result is that on a like for like basis vehicle brakes run much hotter than they used to do. As a result the resin sytem breaks down under temperature and more of the fibres and fillers are lost. If you get them hot enough they will wear out extremely quickly. During mountain descent testing (which is a destructive test to ensure that the material does not easily detach from the back plate - it is only bonded on) you can wear new pads out in one descent (about 18 kms). During the test the discs glow yellow (about 900 - 1000 deg C) and when you get to the bottom they are expected to still work.

This leads nicely to the next myth. You can fade disc brakes but you won't do it easily on a normal road vehicle. Unlike a drum brake which did indeed used to fade, a disc brake has a linear output. Without getting too heavy, a drum brake reacts badly to small changes in friction and a disc brake hardly changes with large changes in friction. A formula 1 car has special pads - usually ceramic based. The only benefit is that the binder system doesn't fall apart after about 1000 deg C. They will run on to maybe 2000 deg C but they are no good for a road vehicle because they don't start to work until about 500 deg C so for most people they couldn't stop their car! The moral is if you want your pads AND discs to last a long time keep them cool. Taking dust covers off is effective but allows contaminants in. Doesn't really matter if you work them hard as you'll burn it all off.

Next myth - "pads have to be rough to work properly". Wrong - pads will only work at their optimum when the are as smooth as glass. Kneel down and look through the wheel of your car at the disc. What do you see? You! - looking back because they should ideally be like mirrors! The pads rely on this finish in order that they don't wear too quickly (as I said they should not be abrasive) and that they can present a perfect contact between the pad materials and the cast iron disc. What really matters is that the development people have used the right friction modifiers and how hard they are pushed together when you press the brake. Think of a train on a track. A 100 tonne loco can pull a 2500 ton train up a hill easily even in the rain. The loco wheels have a tiny footprint and they are pushed into contact with colossal force due to the weight. OK OK I know leaves on the line and the wrong kind of snow but the point is that these will interfere with the contact between wheel and rail.

I'll be glad to answer questions...........

[Robert6920]

hardly a gnat's whisker, it has taken 5 year to wear 1.27mm!

Er, cautious to intervene, but doesn't this assume that the original disc is 25mm thick?? Looking at the front ventilated ones on mine (admittedly a brand new Rav4) they look to be 28.5mm (measured in the twilight - Bothy I think this translates as the gloaming - with a vernier caliper, as I don't have a posh micrometer)

[christine rooks]

hardly a gnat's whisker, it has taken 5 year to wear 1.27mm!

Er, cautious to intervene, but doesn't this assume that the original disc is 25mm thick?? Looking at the front ventilated ones on mine (admittedly a brand new Rav4) they look to be 28.5mm (measured in the twilight - Bothy I think this translates as the gloaming - with a vernier caliper, as I don't have a posh micrometer)

New RAV must have thicker discs (incidently mine is a 3-door so don't know if that makes a diference) as i have measured the new ones fitted with a micrometer and they measure 0.980in(24.9mm)

[Wudzy]

Well slightly off topic but as Sutty says the dealer is lucky to make 1% therefore looking at all those flash outlets, lighting/ heating bills, flash company cars....seems to me from this side of the fence to keep the books balanced the obvious place to reap the rewards from the usually naive punter and take them to the cleaners as professionally as they can when they present there cars for service or repair....and they are real professional at this end of the market more than I can say for quite a lot of so called engineers they employ going on my experience and backed up by what I have seen on the car forums....

I am astounded at the try this bit and charge, still faulty, repeat until fault is found with no refund of the parts that were not needed added to this most dealerships supply one make or perhaps a couple of makes of car, they then have diagnostic equipment to help fault find, over time they should know 90% of faults.........this though is the complete opposite of what seems to be experienced by the punter....

Being a fully qualified electronics engineer I would not be in business if we mirrored the car industry and I am sure that would go for most trades...... what is so unbelievable complexed about a car they are a slow evolution of a industry that has been around for 100 yrs and basically the same engineering.....do I trust garages no...do I trust Dealership garages....double no!

I rest my rant....

Just my opinion for what it's worth..

cheers

John

[Wudzy]

Thanks Anchorman.

Fantastic and knowledgeable post, learned a lot and cleared some myths that I believed.

keep up the good work.

You did though forget to mention what grade of shoe leather is required when experiencing complete brake loss... ;)

Cheers

John

[Hoovie]

One question, Anchorman ...

When the mountain downhill testing is carried out, what sort of backup braking is put into place 'just in case'

[anchorman]

Thanks Anchorman.

Fantastic and knowledgeable post, learned a lot and cleared some myths that I believed.

keep up the good work.

You did though forget to mention what grade of shoe leather is required when experiencing complete brake loss... ;)

Cheers

John

As a matter of fact john, many a true word.............

The original brakes that were fitted to carts were indeed a boot fastened to a lever that was applied to the outer edge af a wagon wheel. The name brake shoe comes from this. Absolutely true.

And that was where Herbert Frood (who with a bit of imagination came up with the acronym ferodo from his name) made his fortune. He studies the antics of the cart men bringing stone from Buxton to the canal at Whaley Bridge and concluded that there was an opportunity!

Friction materials were born in 1897 in Combs, a small village near Chapel-en-le-Frith.

[Parts-King]

Wudzy: Sutty says the dealer is lucky to make 1% therefore looking at all those flash outlets, lighting/ heating bills, flash company cars..

Hmmmm dont get me started........1M investment in showroom upgrade (compulsary) 50K insurance bill, computers, software licencing and digital line rental, you wouldnt believe those costs and add infinitum, oh and forgot the coffee and biscuits in the showroom :D: Never have margins been lower, 0% deals compulsary and paid for partly by the dealer. Sure we turnover millions of pounds, it is the only way to survive, but your ROI IS about 1% average. There is more profit selling hamburgers. Anybody wants a look at my management accounts are welcome to drop in for that free coffee. Fred in the shed pays his rent, heat light power and insurance, and anything else he can freely stick in his back pocket.

Sorry this is off thread and ranting but please dont associate a flash company car with everybody in the dealership waiting to rip you off. We have been selling Toyota for over 30 years and wouldnt be here today if we p****d people off everyday. By all means slate those doing a bad job, but dont tar us all with the same brush, as I have said before, feel free to make judgements, but only when you are in charge of the facts

Christine: I was checking the spec sheet for your discs earlier, the spec for models of your year RAV was 26mm, I havnt checked tonight, but the new discs may be superceeded to a new spec. If you PM the Reg number to me, I can check

Kingo

[bothwell_buyer]

hardly a gnat's whisker, it has taken 5 year to wear 1.27mm!

Er, cautious to intervene, but doesn't this assume that the original disc is 25mm thick?? Looking at the front ventilated ones on mine (admittedly a brand new Rav4) they look to be 28.5mm (measured in the twilight - Bothy I think this translates as the gloaming - with a vernier caliper, as I don't have a posh micrometer)

Lucky bgr - so thats why the Irish RAVs are so expensive - extra meat on the discs!

[bothwell_buyer]

Discs are supplied in ones

Half of what B&Q sell is less than 10yrs ago. Blame all the nutters that complained about Block exemption and importing cars into UK cos it was cheaper.

Build costs are less on all new vehicles like everything else in like its chepaly made cutting corners (TV's Cookers Car components its no different)

Discs have a 50% mark up - Down to dealer to discount for older vehicles

Nobody has mentioned how low the pads were ?

Please also remember Toyota have been learning the european market for the last 10years Pre VVTI, Climate changes compared to Japan, Hence why alloys rust, discs rust, Its a different driving habit in Europe and its taken time to understand

The biggest issue in cost for all dealers is Labour rate increase (Its gone up £25 in 2 years)

And the dealership business is the least profitable business going with a return on investment if your lucky at 1%, Most dont make a profit when the final numbers are counted

Sorry rant over

It gets to me when people whom know nothing about a scenario jump on the slate the dealer off band wagon when i used to see what independant garages do to cars and charge slightly less for doing it.

Where else would you get a 4x4 serviced at a manufacturer dealership for £150

See what Landrover charge for a Freelander service

Hmmmmm

I could not buy an offside disc for my RAv from anywhere, nor made by anyone.