Be interesting to see what the other people you have sold them to find in terms of how centered the rotor is to the caliper bracket. I only have one strut handy to test with so not really enough data to go off yet to revise the design.
My comment about distance to edge of rotor is partly about braking force. With a 305mm rotor, sitting the pad 3mm closer to the strut than it needs to be leaves you missing out on approx 2% additional braking power. I may be oversimplifying the calculation but I get that from 3mm/(305mm/2), being the reduction in leverage.
Shifting the caliper 3mm further out wouldn't be a clearance issue for the 16" wheel I have but perhaps others will find differently?
My engineer brain got the better of me and I have done some research and calculations comparing brake setups. The 'approx. net result' is a massive over simplification. I have simply added % increases in caliper piston diameter and % increase in rotor diameter together and taken off 100% to make it look sensible i.e. not real maths. Things like the radius to the inner and outer edges of the brake pad, aforementioned caliper positioning, need to make other brake setup changes, etc. all come into it.
With that disclaimer done, I have made the following observations:
As is I believe is already reasonably well know, the RX7 upgrade isn't really an upgrade in braking power. Its advantages are lighter caliper, bigger rotor to dissipate heat, etc. Will also feel 'sharper' as the smaller piston diameter means less pedal travel.Some people seem to get away with not upgrading the master cylinder on an S60R caliper swap, but thats only an increase in piston area of 111.1%. I suspect the 121.6% increase with Ford calipers will result in a long pedal and a need to upgrade the master cylinder. The couple examples of Ford calipers on a 240 that I have seen pictures of also increased the master cylinder diameter. Some more research could be done into what people have found/done with the Cadillac ATS Brembo upgrade on a 240. From what I gather that has 42mm pistons so basically the same as the Ford calipers.Increasing the master cylinder diameter adds another variable to the calculation and would reduce the net increase compared to a stock 240. Bigger master cylinder diameter will pump more fluid, however there is less pressure for a given pedal force. For example if you needed to upgrade the master cylinder to run ford calipers on S60R rotors, it wouldn't be the fairy tale increase my table suggests when compared to say a stock master with S60R calipers and rotors. I would have to think on this some more but... I don't think an increase in brake piston diameter will increase braking power without also having a longer pedal travel. For a fix amount of pedal travel and fixed pedal pivot points, the increase in brake caliper piston diameter would be offset by the need to increase the brake master cylinder diameter. Therefore main ways to increase braking power without impacting pedal feel is through increasing rotor diameter and/or a larger brake booster.
