Disc brake replacement

[brad]

I'm pretty sure machining only takes a fraction of a millimetre off the discs - I've seen stats on discs where the max and minimum thicknesses are only 2mm different!

It probably is if you are doing your own discs and are happy to make 3 or 4 small passes to remove the minimum but if your doing a customer car, then you only want to make a heavy truing cut, then a light finish cut & bolt the thing together as quick as you can.

When I was spannering, I didn't even attempt to machine VW discs as they were so thin to start with and rarely machined above the minimum thickness - that was a long time back though. Audi Fox was popular.

[blutopless2]

have read over the years that most european cars require disc replacement from around the 40,000 mark.
My nbc is up for another service soon, done around 60,000k's (5 years) so will be interesting to see what the pad/disc wear is like.

[No457 Snowy]

Just checked my workshop manual and here's some specs for those that haven't got them:

For front pads the new pad thickness is 19.7mm, including backing plate. The minimum thickness wear tolerance for the pads is 7mm, including backing plate.

For rear pads the new pad thickness is 16.9mm including backing plate. The minimum thickness wear tolerance for the pads is 7.5mm including backing plate.

For the front disc rotors new thickness is 25mm and the wear limit is 22mm.

For the rear disc rotors new thickness is 9mm and the wear limit is 7mm.

Mine have the factory wear indicator connections fitted, so the dash warning light should come on when the pads are due.


Cheers,

Snowy

[ranton-inc]

It probably is if you are doing your own discs and are happy to make 3 or 4 small passes to remove the minimum but if your doing a customer car, then you only want to make a heavy truing cut, then a light finish cut & bolt the thing together as quick as you can.

When I was spannering, I didn't even attempt to machine VW discs as they were so thin to start with and rarely machined above the minimum thickness - that was a long time back though. Audi Fox was popular.

The MKIV R32 has

334 x 32mm discs on the front the over all minimum thickness is 30mm

[moniker]

Just a thought 'though, why is it bad for discs to get thinner? is it a heat issue or can ventilated discs could get weak if too thin?

[ranton-inc]

Just a thought 'though, why is it bad for discs to get thinner? is it a heat issue or can ventilated discs could get weak if too thin?

i think its to do with casting surface tensions and heat dissipation ie they are more suseptible to warping etc...

[sdr]

Ahhh...Cheers for all the replies. I guess I was just a bit paranoid (to use a better word) that I was being taken for a ride.

On another note, I found out after my tune last week a few interesting things about my car.

60k and apparently the car was still on the original coolant, and a few other things. All I know is that is running a whole lot better after the service.

[D3bb4]

Red coolant lasts up to 250 000kms i think the figure is from top of head.

[brad]

Just a thought 'though, why is it bad for discs to get thinner? is it a heat issue or can ventilated discs could get weak if too thin?

Think of the disc rotor as being a heat sink.

• Less mass means less ability to absorb or dissipate heat.
• Less structural integrity & increased heat increases likelihood of warping.
• They can get thin enough that the brake pad can fall out of the guide slots in the caliper.
• They can get thin enough that the piston will pop out of the caliper
• More heat means increased likelihood of hotspots, cracks and ultimately, structural failure.

[gslrallysport]

Bendix is the only non-OEM brand that doesn't void manufacturer warranty.

That is definitely NOT true! Why is Bendix any different to any other aftermarket manufacturer? In fact, the exact ACCC ruling is:

"If a part is non-genuine, but is interchangeable with the genuine parts, it could be seen as being fit or appropriate for the purpose and would therefore not void the manufacturer's warranty."

How is that a Bendix only thing? Bendix pads would definitely be in the lower range of quality and performance vs. dollars...