Brake disc help please

[WilliamBall]

Joolz, if by 'smaller cerby' disk you mean ones that fit a 4.2, then I recently fitted drilled items - same diameter as standard. Definite guarantees are 1) the drilling is 'left handed' only. 2) 'right handed' drilling not available. 3) vanes are straight, so disks really are actually intechangable. 4) no sign of AP logo.

As to rumour, I was told that they weren't AP disks. Also told that although they fit straight on a 4.2, they're actually off a Tuscan. I am aware of other 4.2 Cerbies now running these 'Tuscan' drilled front discs and I beleive they are holding up better than the standard undrilled disks.

WB

[joospeed]

yep for sure they first saw light on the tuscan. drilling is actually a bad way of venting the disc / pad gasses - cracks often start from the drillings although tvr do sem to countersink / radius the drillings which is good. grooved discs are much better for hard use but don't look quite as sexy...
what pads do you use william?

[jedsteel]

Thought I'd show my face again after confusing matters with my earlier claim that vented discs scoop air in from the outer edge (load of old cobblers - apologies). However, I can confirm that I have replaced the front discs on my late 97 4.2 Cerbera with one-piece, drilled, straight vane items which the AP factory tells me, over the 'phone, are not AP items if the disc does not sport the AP reference number on the innermost edge of the disc. Mine were supplied by a franchised TVR dealer and don't have this reference. Whatever. The really incredible news is that TVR appears to be offering cars with incorrectly handed discs on the one side. Could this lead to braking imbalances, or at the very least different disc wear rates between the two sides of the car, as one disc is cooled as it was designed to be, while the other is denied the same cooling capacity?

[GreenV8S]

quote:
Thought I'd show my face again after confusing matters with my earlier claim that vented discs scoop air in from the outer edge (load of old cobblers - apologies). However, I can confirm that I have replaced the front discs on my late 97 4.2 Cerbera with one-piece, drilled, straight vane items which the AP factory tells me, over the 'phone, are not AP items if the disc does not sport the AP reference number on the innermost edge of the disc. Mine were supplied by a franchised TVR dealer and don't have this reference. Whatever. The really incredible news is that TVR appears to be offering cars with incorrectly handed discs on the one side. Could this lead to braking imbalances, or at the very least different disc wear rates between the two sides of the car, as one disc is cooled as it was designed to be, while the other is denied the same cooling capacity?

I don't think it makes enough difference to worry about. In theory, the 'pointing forwards' vanes produce more pressure and the 'pointing backwards' vanes produce more flow. It's hard to say which would produce better cooling in this case, I'd guess that there's hardly any back pressure so probably the 'flow' setup but the difference wouldn't be dramatic.