Brake pad thickness for WOF Page 1 / 2

moby, May 2, 10:58am
Recently took the family hack Corolla for a WOF and got knocked back on front brake pad thickness. Had them replaced (same garage, only $100 so not too bad) and asked the WOF guy what the minimum thickness was and he was rather vague, though we both agreed 2mm was a bit lean. Anyone know what the actual minimum is, just out of curiosity.

pauldw, May 2, 11:17am
Depends on make. My car's service manual says 2mm front 1mm rear. AFAIK Toyota say 1mm is limit. Usually 1 pad will be on limit while others could be 1 or 2mm more. By the time you're down far enough you have to check you may as well replace.

ema1, May 2, 11:35am
Thing you must understand with pads worn down to that extent is greater degree of heat transfer to the pistons thus the fluid operating them and the obvious disc damage that can result when the metal disc pad baking comes into contact with the disc.
Also and most important the braking performance falling off.
It's not worth the risk of having suspect defective brakes . period.
Pad wear rate varies often too between the pads as poster #2 states.
It doesn't cost to check em and whatever the cost of repair/replacement it should not be considered a factor but as necessary as it's routine maintenance in my book.

kevymtnz, May 2, 11:38am
25-33% is my limit

ladatrouble, May 2, 12:12pm
Depends on car and usage - eg, earlier Commodores were 1.5mm, but the SS which took the same (but higher quality) pad was 3mm, and most high performance cars are 3mm. I work on 1.5mm as being the most common minimum, but often you can only get a good look at one pad, the one you can't see, or the opposite end of the one you can may be much lower.

mugenb20b, May 2, 7:27pm
As a guideline, it's 2mm, but don't forget, it's only a visual inspection.

clark20, May 2, 8:14pm
Pad thickness is not a point for rejection, if the brakes work properly then they should pass. As a safety point the owner should be made aware of it.

kazbanz, May 2, 8:47pm
Moby-I'd be getting the inspector to show you where the regulations give minimum pad thickness.

llortmt, May 2, 10:02pm
The armchair AVI has spoken LOL!
It is a reason for rejection if the pads friction material is below that of the manufacturers spec.
As said 2mm is a good general guide, any friction material thiner than its metal backing is normally a fail but it does vary car to car.

franc123, May 2, 10:14pm
Haha WRONG. If the rotors also appear to be excessively worn this can be chucked out too, unless it can be proven otherwise through checking against the minimum spec's. The performance test is only one component of what the brake system has to pass.

mrfxit, May 2, 10:20pm
LOL & yes correct.

Visual 2mm limit based on average of Manufactures spec's
In general domestic terms, 2mm for front brakes & 1.5mm for back brakes.
1.5mm being the wof minimum but you would need to prove the 1.5mm consistent thickness to get a wof on them

Pads often wear on an angle & the 2mm minimum normally allows for this happening.
Theres also commonly a groove across the middle of the pads (dust removal) & if thats almost or has gone then yes they definitely need to be replaced ASAP

Some allowance in a wof can be made for pads that look over the 1.5mm minimum but personally that depends on the vehicle & how it's likely to be driven (including loaded/ trailers /high speeds/ aggressive driver etc)

mrfxit, May 2, 10:25pm
Yep also correct.
If a brake rotor shows a deep lip on the outer edge then it indicates a badly worn rotor.
Again, it needs to be fixed & proven that the rotor is within manufacturers wear limits.
Same rules can apply to the rotor inner edge but a trained eye can normally judge if it's badly worn or recently machined.

mrfxit, May 2, 10:30pm
About 10 years ago, A brothers ute had been passed with 1mm front pads.
On an interIsland trip a few months later, 1 pad chewed the rotor on a rather steep & long hill.
It had heated enough to separate what was left of the pad from the backing plate.

attitudedesignz, May 2, 10:42pm
That's actually a pretty good guide come to think of it.

clark20, May 3, 7:16am
So this does not work if you cannot see the pads? So most cars with steel wheels would be nearly impossible to see? Don't worry I change well before then, but what happens when I have 2.5mm and WOF inspector says no, and you prove that they are 2.5mm who pays for the check?

clark20, May 3, 7:28am
And whose fault was that?

franc123, May 3, 7:34am
Piece of piss mate, clauses 22 and 23 in RfR cover it

http://vehicleinspection.nzta.govt.nz/virms/in-service-wof-and-cof/general/brakes/service-brake-and-parking-brake

There are very few instances where pads aren't visible and measurable from underneath the vehicle, you can use a small round telescopic mirror and torch to see them in most cases, you can buy special plastic feeler gauges to check the pads IF you can get them in the space that's there. It is mostly done by eyeometer though. Manufacturers tolerances generally vary from 1-3 mm minimum but you' d have to be pretty harsh to fail any that had at least 2 still on them, it would pass with a warning. If the minimum was only 1 and a rejection occurred over this then you could always prove to the inspector this was the case from manufacturers data or Autodata etc.

clark20, May 3, 7:35am
Actually told to me by a AVI, so now what do you think?

llortmt, May 3, 7:48am
Birds of a feather flock together!

clark20, May 3, 8:02am
I said rules, not the guide. I found them anyway,

franc123, May 3, 8:08am
And it was given to you. They are one and the same thing.

clark20, May 3, 8:50am
No they are not. The VRIM is not the rules. This is

http://nzta.thomsonreuters.co.nz/DLEG-NZL-LTSA-T.LTR-32014.pdf

mrfxit, May 3, 8:56am
BOTH.
Owner for not being a bit brighter about maintenance & the wof inspector for not looking properly, (presumed not looking properly/ looking the other way)

franc123, May 3, 8:59am
That document is not used by AVIC's when determining passes and fails FFS, it means nothing. The VIRM is the only thing used at WOF level.

pauldw, May 3, 10:32am
2.5 (9) b refers to being within manufacturers tolerances. That's where pad and disc thicknesses come from.

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