Pad & disc overlap

[Bibby]

Apparently Alcon recommend that their pads sit with a 1mm overlap over the edge of the disc circumference. All factory car setups I have seen have had the pads sitting almost to the edge of the disc, but never overlapping.

Has anyone anything to share on this? I find it quite interesting and am curious to know why Alcon recommend this kind of setup.

This will of course leave a lip on the pads (as opposed to the edge of the discs) which seems a little odd. I'd have thought this would leave the pad more susceptible to breaking up.

[twoqu]

Hi!,

I've lifted this from a PDF about installation of an Alcon H type caliper:

Installation General Information
When the pads are fitted, the top edge of the friction
material should be 0.5mm above the disc outside
diameter. The disc must be central in the caliper
within +/-0.5mm. Check that the pads can be
inserted without any undue force and that they do
not touch either the disc bell or the upright under all
conditions. To prevent overheating, radial
clearance between the disc and caliper must be
more than 2mm in all directions.
Bleed screw torque: 18Nm Cold, 14Nm Hot
Pad retainer bolt torque: 12Nm Cold

[Lee]

Disks expand when hot. I worked out how much my 362mm disks would expand to ensure adequate caliper clearance. I assumed a disk temp in excess of 800C to ensure adequate caliper clearance when on track. That temp is too high for the iron disks as the attrition rate can increase depending on pads but it makes things relatively conservative if you leave a bit extra.

Doesn't matter if pad overlaps disk or vice versa so long as the overlap is not excessive (ie more than 1 mm or so).