Brake question

Those of you that have designed and built your own car, how did you decide to mount your brake calipres on the leading edge or trailing edge of the rotor?

I noticed while waiting first in line at a red light friday that cars in cross traffic had leading and trailing calipres both front and rear with no discernable rhyme or reason. The fronts may be leading and the rears trailing, or vice versa. The fronts and rears are leadin or trailing. SUV, Mini van, Pick-up, Luxo-barge, Porsche, Aston Martin, even a Ferrari went by.

Is it an engineering (this works better based on these parameters) decision? A parts bin (whatever is available) decision? Or is it a packaging (the tie rod ends, swaybar links, whatever is here so we need to put it there) decision?

I dont know why I thought of this now. All these years of playing with cars and I never thought about it or looked at what has what.

i prefer the appearance of trailing on front axle and leading on rear, but the simple truth is that it comes down to packaging.

The engineer in me agrees with angry- the polar moment should be reduced by having calipers nearer the COG... depending on other packaging factors

The placement on the front on some cars is determined by the placement of the steering arm and the steering rack. IF in front of the center line of the wheel them the caliper will be on the trailing side. The opposite is true if a rear steer car. Of course on some cars I've seen the rack is mounted up high and acts on a steering arm on the strut tube so the caliper could be placed where ever the designers want.

The 15 lbs of caliper moved 8" or so isn't going to matter much. Mount them wherever you want.