>> Cross drilled through the disc and ventilation pockets.
>
[quoted text clipped - 34 lines]
> grooved on the surface, BUT the holes don't go right through the discs
> (they're just "dimples" really) so they don't lead to cracking.

Signature
Keith Willcocks
(If you can't laugh at life, it ain't worth living!)
>>> Cross drilled through the disc and ventilation pockets.
>>
[quoted text clipped - 40 lines]
> is the benefit of drilling the discs
> and having grooves?
When you apply the brakes, the pad pushes against the disc. Some of the pad
is burnt away, producing brake dust and gas.
Brake fade is caused by both overheating pads, and a build up of gas and
burnt material between the pad and disc.
Grooved discs provide a path for this gas and dust to exit from between disc
& pad. The less "stuff" between the pad & disc, the more efficiently the
braking system works.
Drilled discs *that-are-designed-to-be-drilled* will suck air into the holes
as they turn, and throw it out of the vents on the outside edge of the disc.
Greater airflow through the disc, means greater cooling, means less fade.
Drilled discs that are just normal discs with holes in, don't do anything
except crack after a while.
With modern pads, both problems above are much reduced - but they do still
exist. If your braking system isn't really upto the job (ie, pretty much
every OEM system on the road today, discounting *proper* sports cars) then
you can make very noticeable gains.
Have a read of http://www.nomgle.com/brakes.pdf if you're interested
further.
Keith Willcocks - 14 Oct 2005 16:05 GMT
>>>> Cross drilled through the disc and ventilation pockets.
>>>
[quoted text clipped - 65 lines]
> Have a read of http://www.nomgle.com/brakes.pdf if you're interested
> further.
Thanks for that, it is all new to me but does make sense. Presumably if
the manufacturer (i.e. Peugeot) were to fit the equivalent of drilled discs
it would solve the problem of discs warped due to heat which seems to affect
these cars (my new set warped after less than 10,000 miles and I regard
myself as a gentle driver).

Signature
Keith Willcocks
(If you can't laugh at life, it ain't worth living!)
Nom - 18 Oct 2005 12:03 GMT
>>>>> Cross drilled through the disc and ventilation pockets.
>>>>
[quoted text clipped - 72 lines]
> warped after less than 10,000 miles and I regard myself as a gentle
> driver).
If you warped them driving gently, then it wasn't due to heat.
If your discs are hot, and you stop with your foot on the brakes (ie, at
traffic lights) then the bit under the pad won't cool down as quickly as the
rest = warped discs.
If your hubs aren't quite straight, then neither are the discs = warped
discs.
If you stop your car when the discs are hot, then the pad may burn onto the
disc slightly, leaving a desposit of X thickness = same symptoms as warped
discs.
There are a bunch of other reasons too ! Suffice to say, you have to get
your discs VERY VERY hot to warp them through heat alone.
Keith Willcocks - 14 Oct 2005 16:14 GMT
>>>> Cross drilled through the disc and ventilation pockets.
>>>
[quoted text clipped - 65 lines]
> Have a read of http://www.nomgle.com/brakes.pdf if you're interested
> further.
I have just read your piece on brakes and very interesting it is too. I
thought you might like a totally useless bit of historical information. We
think power assisted braking is pretty modern but it is not. Centuries
ago, when real horse power was all you got, the brakes on a cart would be
operated by a rope connected to a lever beside the driver. They used to
take a loop of the rope around the front hub. Then, when you pulled on the
lever, the rope tightened on the hub and the turning force of the hub
greatly increased the power applied to the brake. As they say, there ain't
nothing new under the sun.

Signature
Keith Willcocks
(If you can't laugh at life, it ain't worth living!)
Nom - 18 Oct 2005 12:04 GMT
>>>>> Cross drilled through the disc and ventilation pockets.
>>>>
[quoted text clipped - 67 lines]
>
> I have just read your piece on brakes and very interesting it is too.
The PDF isn't mine - I just found it on my travels :)
I've put some other bits up at http://www.nomgle.com/ if you're interested
in "car systems".
> I thought you might like a totally useless bit of historical
> information. We think power assisted braking is pretty modern but
[quoted text clipped - 5 lines]
> power applied to the brake. As they say, there ain't nothing new
> under the sun.
Nice !