Another 996 Disc Option??

[4WheelDrifter]

Will's right. I had some disks on my old car that had holes like that, and they lasted ok. They also had a few grooves in. I think it's that sharp edge causing the stress. A nice radius normally helps.

[Keeper of The Kitten]

Yes, sharp edge causes stress - engineering fact! That's more than enough reason to remove them in most circumstances. But if the sharp edge is functional, removing it is not necessarily a good thing. That's why I would argue against the drilling option altogether, the grooved option does the job with less vulnerability.

__MDC__

[4WheelDrifter]

The idea of the drilled holes is to make sure the pad makes full contact with the disk, so there are some benefits.

[Jamo]

I'm looking to get a brake disc to finish off my 996 conversion, and I wanted a cross drilled disc. The only one I can find that is just cross drilled is a brembo disc at £360 a pair. Does anyone knoe where I can get a Zimmerman cross drilled disc from???

Secondly I was going to use the 323mm x 30mm A8 option, but I've hear this is very tight on clearance. I didn't want to use the 314mm A8 disc, as I don't like the thought of the pad overlapping the disc.

Has anyone considered using the Allroad or the A6 disc that is 321mm by 30mm. It has the same PD, is this a viable option. I've attached a family album pic. It seems to me to be the closest size to the original Porsche disc????

What size alloys have you got? as the 323mm will fit under 17" or 18" no problems.

[S2Roo]

I've got 17" S4 Alloys, I'm more concerned about the caliper being close to the disc.

I'm told theres only 1.5mm clearance between the disc and the caliper???

[4WheelDrifter]

I've got about 3mm clearance on my 323mm disks. And plenty of clearance under my 17s.

[Jamo]

I've got 17" S4 Alloys, I'm more concerned about the caliper being close to the disc.

I'm told theres only 1.5mm clearance between the disc and the caliper???

See 4wheeldrifters post, MartinJS also ran the same setup as you have at present with no complaints before upgrading to S8 alloys.

[S2Roo]

That sounds promising!!!

Thanks 4wheeldrifter and Jamo, I shall proceed as planned and see how I get on .

[missmouse]

Ive only got about 1.5mm between the disc & the inside of the caliper on mine. In fact the pad retaining clip was touching slightly so I have bent it!
Im not sure about the idea of spacing the caliper out. What has anyone else used for this? Big washers or custom made spacers?
Plenty space between the (17") wheel tho.

Simon

[Keeper of The Kitten]

The idea of the drilled holes is to make sure the pad makes full contact with the disk, so there are some benefits.

Not true.

Disc grooves and sometimes cross drilling are frequently used on racing brake discs to clean the surface of the pad and allow gases produced to escape

True.

D = Cross drilled, drilled holes chamfered. Still preferred with some pad materials but can compromise disc life.

Note that AP chamfer the cross drillings, but still say it "can compromise disc life".

__MDC__

[4WheelDrifter]

The idea of the drilled holes is to make sure the pad makes full contact with the disk, so there are some benefits.

Not true

Disc grooves and sometimes cross drilling are frequently used on racing brake discs to clean the surface of the pad and allow gases produced to escape

confusing.

[Pembo]

Quote:
Originally Posted by AP Racing Website - Disc Face Types
Disc grooves and sometimes cross drilling are frequently used on racing brake discs to clean the surface of the pad and allow gases produced to escape

That is right.

[Keeper of The Kitten]

It's always been my understanding that the face details of a disc provide something of a "cutting edge" to remove the small amounts of glazed material from the pad surface, which is confirmed by the aformentioned data from AP, one of the leading brands.

As the heating of pad and disc will also produce gases that have to go somewhere, grooves or cross drillings serve a second purpose to clear those gases.

__MDC__

[4WheelDrifter]

As the heating of pad and disc will also produce gases that have to go somewhere, grooves or cross drillings serve a second purpose to clear those gases.

Make your mind up man.

[Crawford_S2]

Just took my Zimmerman drilleddisks off after fairly hard use but only half way down the first set of pagid fast road pads and they are fooked, totally shabbed!

Never buying those again, and the wholes were countersunk.