Min thinkness for VT calipers

[tortfeaser]

I've got a Holden Camira rally car (don't laugh) that currently has VP calipers and 273mm Peugeot 504 disks.

I'm thinking of upgrading to VT dual piston calipers and need a suitable disk. Height needs to be around 43-47mm. There are a few contenders, mostly 5 stud so redrilling for 4 stud is difficult.

However, the Ford Focus ST170 disk is 4 stud, and 300m dia (to machine down to the 296mm max I can fit), but thickness is 24mm.

I understand the min thickness for VT disks is 25mm (from the DBA catalogue). Is this a minimum thickness for machining, or will the pads fall out of the caliper if the disk is any thinner than 25mm? IE, can I use the 24mm thick ST170 disks in the VT caliper?

Marc

[bobg]

The minimum thickness specification for standard VT rotors is based mainly on the ability [or lack thereof] of the worn rotor to absorb and dissipate heat without warping. As the rotor wears the material between the vanes gets thin and warps easier. But if the rotors were originally designed to be thinner to start with [and thus have smaller vent ducts] they could be just as effective at resisting warping.

There are plenty of VTs getting around with rotors below the recommended thickness [some by several millimetres] and while it is not good [and it is unroadworthy so you might blow your insurance if braking was a factor in a crash] I have not heard of anyone having the pistons pop out or the pads coming adrift.

Remember, if the Ford rotors are 1 mm thinner overall, just replace the pads when they wear to minimum pad thickness plus 0.5 mm. The pistons and the pad backing plates in the VT calipers will then be in the same relative positions as they would be if they had standard VT rotors worn to their minimum thickness.


Regards

Bob G