Brake knowledge

If I remember correctly, Matt covers this in his vid as well, it's to allow for expansion to prevent warping and not about disc alignment at all. So cleaning that area will maintain the gap necessary to allow the expansion.

However when reading the EBC article further, another of Matt's videos comes to mind, that of materials expansion when heated, specifically relating to the expansion of holes in materials. In that he states that when materials are heated all holes expand outwards and never inwards (Unless otherwise constrained). That we know to be correct and is of course why we heat casings to remove bearings but this also conflicts with the EBC article which states:

So, maybe we can't rely on the EBC article - at least not completely.

Matt's video here:

This is getting interesting! ...

Absolutely, I think he gets a bit carried away. The last one was when he was talking about oil viscosity. He clearly had some knowledge of the subject but not as much as he thought. That's the one I was referring to earlier.

However, he is quite a clever guy - even though he may disguise it at times(!) - and practical with it as he works in testing and R&D type roles. But more than that he obviously reads lot's of tech stuff just for the fun of it.

I thought when metal expands under heat it expands in all directions. A hole in the metal will expand at the same rate as the rest of the metal would expand. I.e. if the hole were just a circle drawn on it would still get bigger when hot.

But that hole thing only applies to the ventilation holes in the rotor. Not the inside circumference of the rotor which would also expand. The whole (hole?) thing will expand outwards won't it? So the outside will go expand out and the inside will expand in.

I think what they are saying is the buttons act as bearings to allow heat expansion, rather than to make the rotor float to allow it to align properly and minimise drag.

They are saying you only need movement in one plane and that excess side to side movement can lead to pad kickback which can cause accidents like Michele Pirro's one at Mugello this year:

The theory follows the same as the ventilation holes as the disc is effectively just a piece of plate with a big hole in it.

Anybody got an old out-of-spec disc they can put in the oven and do the test?