Mileage verification?

Completely. Why not?

Mk1 Ford Focus. Manufacturer's specification when new = 22mm. Wear limit = 20mm. Measured at 21mm, with a significant lip which I removed with an angle grinder.

Chris

Quite - I've never had a car fail because of this.

Because the lip isn't swept by the pads it is likely very rusty - so even thicker than if clean.

There is zero reason why such a lip will effect braking efficiency anyway. The pads don't touch it. That's why there's a lip. ;-)

Seems no one else has one on here either then - apart from Mr Doom who you agree with. You make a very nice couple.

It's a *pretty* good indicator of how badly the disc is worn. But what they *should* do is mic it up and refer to the manufacturer's data for minimum permissible thickness.

[...]

Who is 'they'? If you mean an MOT tester, then you clearly have little idea of the basic concept of such a test.

Oh, and as my experience indicates, a wear lip is a poor guide to the wear level of a disc.

Chris

But without knowing how the car has been driven it tells you nothing about mileage. Discs aren't worn out by driving miles, they're worn out by braking.

If you're correct then it's my mistake for assuming the way things are done in my country are the same as the UK; my apologies if that's not the case.

[snip]

So where do you live?

My last BMW had the minimum thickness engraved on the hub of the disc. Simple enough to measure with a suitable micrometer. Which fits over any lip.

Yep, original Ford discs are the same.

Not permitted to be done as part of an MOT though.

Chris

Or get replaced because one has warped slightly. As with my wife's low mileage Matiz that is only a town runabout and totally incapable of "spirited" driving, so no, the disks haven't been worked hard. SteveW

Probably explains several sets of brakes I've looked at lately where they're on at least their 3rd set of pads and the discs are heading towards see-thru! Presumably most garages only want to be bothered with nice quick jobs and just do the pads.

Clutch life tends to be determined by how many starts from rest you do. No matter how well you change gear you can't eliminate wear when starting off. So a car which cruises the motorway will likely have a much longer clutch life than one used in town. And the same sort of thing applies to brakes. The way the car is driven can have a big influence - but traffic conditions are outside the control of the driver.

Germany currently.

Unless you've got a pretty weedy car, doing that is going to result in hitting the car in front in traffic?

I'm a pensioner. ;-) Careful use of the clutch isn't age related. And if you wish to do a fast getaway, it's up to you.

But not the gearbox, if you do that often. You'd need to match engine speed to within a fraction of an RPM to avoid stress to the box.

Unless you have a crash box it's not clutchless, just a different clutch. This poor little thing.

What you are doing is buggering the weedy little metal to metal cone clutch on the synchromesh. The cone clutch is only designed to bring the layshaft, input shaft and clutch disk up/down to speed. Adding the inertia of the flywheel, pressure plate and crank to that is a massive overload.

Unless you have a stock of 2nd hand gearboxes, gearbox rebuilds and parts to replace worn synchro are way more expensive than a clutch kit. To replace the synchro cone you have to replace the gear, gears have to be replaced as sets and that means if it meshes with a gear that is fixed on a shaft with other gears (like the layshaft) then you are replacing every gear that meshes with the gears on that shaft. For a 5 speed RWD box 1st, 2nd and 3rd are usually fixed on the lay shaft and have to be replaced as a set. On FWD 5+ speed indirect gearboxes there can be as many as 4 gears fixed on one shaft.

Only gearbox that can take clutch less changes are dog boxes (motorcycle and race cars). It's still abuse, eventually a shift is missed and it chips the edge off a dog tooth. Strip the box, stone the burr off.

I remember my Vespa recommending clutchless changes. But it had a spring drive in the transmission to reduce the impact on the dogs. There are springs in most clutch plates which have a similar effect - but aren't going to stop wear on the synchro.

If it's a real high-miler, it could have had several disc changes, plus I have managed 70k miles out of a set of discs/pads, a colleague has trashed a set in 12k. Different cars, but it shows how different driving styles and/or road conditions can affect thinks wildly.

I don't know if others do this but some VAG cars store a calculated mileage figure in the engine ECU as well as the recorded one in the instrument panel, and with diagnostic gear you can compare the two figures.

The last set of discs I fitted myself had a dimple drilled in the swept area drilled to minimum thickness, so when it disappeared, it was time to replace. ATE ones, I think.