Disk brake pads - legal minimums?

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andrewNZ

2487 posts

Uber Geek
Inactive user

#941932 27-Nov-2013 23:15

Technofreak:
andrewNZ:
If you're not happy, get a second opinion (you can probably ask a mechanic for no charge), don't just challenge them based on your opinion or opposition to their decision. There are professions (mine included) where peoples lives, your entire carrier and livelihood rest on every single decision you make. There is nothing more insulting than someone asking your professional opinion and then challenging it because they don't like it.

I didn't challenge them based on opinion it was based on fact. They claimed 3mm none of my pads were under 3mm, plus the workshop manual specs say 1mm minimum. The was even a wear indicator on the old pads which showed the 1mm mark.

Just because they are professionals it doesn't mean they don't make mistakes. Are you telling me that if a professional gave you advice you knew to be incorrect, you would willingly accept that advice and wouldn't challenge it? That's even more likely to put lives at risk.

If anyone gets insulted because their opinion has been questioned when they are in the wrong, then I would suggest they need to take a close look at themselves. They might well be embarrassed, but insulted??????

I didn't say professionals don't make mistakes.

I'll simplify what I said.
Get a second opinion to make sure your objection is based on FACT. Opinions from forum members who haven't laid eyes on the items in question, and things you read, aren't necessarily proof the decision is wrong.

techmeister

310 posts

Ultimate Geek

#941933 27-Nov-2013 23:50

Bung:
techmeister: I am a mechanic and I can tell you that it is generally considered that if the pads are any less than 3mm then they should replaced, however that has nothing to do with a WOF inspection as far as I know if it passes the brake test it is of WOF standard and should pass.

Even though the warrant inspection only covers what is visible, condition can be a reason for rejection as well as performance. This is covered in the inspection manual http://vehicleinspection.nzta.govt.nz/virms/in-service-wof/general/brakes/service-brake-and-parking-brake

Yes condition can be a reason for rejection of course, things like rusted brake pipes, perished brake hoses, and leaking axle oil or brake fluid.

This is not the case here as it was failed on brake pads being to low, in fact they were well within vehicle specs and would not be considered unsafe by any mechanic or the manufacturer.

It is the same with ball joints and tie-rod ends these must be within manufacturers specs to be considered safe but I doubt any WOF agencies measure each one and even know what the specs are of each make and model of vehicle they test.

It is very difficult to accurately measure how much brake pad is left on most vehicles without removing parts, my point being the WOF inspection is a very visual inspection and if the inspector cannot see accurately they should just issue a warning.

The only thing the OP can do is get a second WOF inspection done and it may pass, however it might be cheaper just to replace the pads and be done with it.

Goosey

2839 posts

Uber Geek

Subscriber

#942527 28-Nov-2013 21:07

Technofreak:
Goosey: So what was the brake test results from the check sheet then?
I.e. Service brake, and front and brake balance etc?

B1 Brake service performance: 200 on all four wheels, Pass
B2 Service brake balance: Pass
B3 ABS self test: Pass
B4 Parking brake performance: Pass

I thought they put down a percentage and that shows any imbalance etc?
I.e. Some inspectors mount a device inside the car and brake test or do this on those ramps and rollers.

gumboot19

52 posts

Master Geek

#942539 28-Nov-2013 21:55

Hi Goosey. the meter put on the floor is called a "tapley meter" (brand name). Most testing stations have a set of rollers and a visible readout.
I'm a little mystified by all the responses, nobody has stated one of the basic rules of brakes:
"Brake shoes or disc brake pads have to dissipate all of the braking effort as heat (change from mechanical to kinetic energy). The thinner the brake pad, the less heat is able to be dissipated. If too much heat is transferred to the backing plate, normally the bonding material (glue) gives up and the lining falls of the backing plate.
Therefore the thinner the brake pad or shoe, means that less heat is able to be absorbed by there friction material and the more likelihood of the brakes overheating in an emergency situation.

If my brake pads were worn down to your said thickness and it was noted by a wof testing station, I would thank them for their vigilance and replace them.

The manufacturer suggests a minimum thickness so that their vehicle will stop, maybe not within NZ vehicle testing rules which state that a vehicle must stop in a certain distance from a certain speed.

To all other members of this site who have given their time to reply, I will try to politely say: "You have no right to dictate who lives or dies by your opinions, if the brakes do not work as NZ road regulations require.
Most people use a wof as a safety feature and do little maintenance in between, possibly this inspector was trying to keep you and your family safe? Other peoples opinions will not pay your insurance premium if you have an accident.
Cheers, Darren

Bung

6504 posts

Uber Geek

Subscriber

#942547 28-Nov-2013 22:25

gumboot19: To all other members of this site who have given their time to reply, I will try to politely say: "You have no right to dictate who lives or dies by your opinions, if the brakes do not work as NZ road regulations require.
Most people use a wof as a safety feature and do little maintenance in between, possibly this inspector was trying to keep you and your family safe? Other peoples opinions will not pay your insurance premium if you have an accident.
Cheers, Darren

Well you've certainly brought a lot of opinion with you.

Did you miss that the car passed the performance test?

The brake pad thickness exceeded the regulated amount which is as specified by the vehicle manufacturer.

Yes pad thickness does affect heat transfer to the brake fluid but the disc rotor is where heat is intended to be dissipated.

gumboot19

52 posts

Master Geek

#942562 28-Nov-2013 23:00

Hello Bung.
points taken and noted
In my opinion the words Performance and specification are not the same.
Yes you are correct in that the brake pads should dissipate their latent heat to the disc, but heat travels in all directions. Was the backing shim behind the pad in place (anti squeal shim and heat-soak spacer) when the vehicle was presented for a wof? Disc thickness etc...

there are many different opinions here but none of them involve our own car or family safety.

What would you do in this situation? who would you trust?

Cheers, Darren (reg mech engineer # 33881)

(have checked and issued woof's for a year or two..., also done the odd course on car braking and worked on a few cars and light trucks...)

DrDee

269 posts

Ultimate Geek

#942872 29-Nov-2013 12:00

I was issuing WOF's for about 10 years, but that was 10 years ago.

When I was doing WOF's the regs only dictated that the brakes had to stop you/be balanced/no visible leaks etc. There was no requirement on pad thickness as on a lot of cars this would then involve removing wheels and in some rare cases removing callipers as well. And then there are drum brakes.
All we could do at the time was note the fact that we could see the pads were getting low and suggest that they get them changed, even if steel on steel.

Man I had some doozies in my day tho. I had a car that you could see the road through both the rear seat footwells, the rear of the drivers seat mounts were not even attached to anything and I failed it hard on structural rust, the lady flipped at me because "how am I meant to take my kids to school now!". Also I was checking seatbelts in a van and buckled up the drivers belt and gave it a tug, the stalk broke off the floor and the driver went ballistic saying I had to buy him a new seatbelt.... CF bedford with a beer crate for drivers seat and a pair of vice-grips for steering wheel... man I could go on all day LOL

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