rear caplipers....

Do they go in front of the hub or behind? And Why So?

Does this play into the anti squat while braking?
Does IRS differ than Solid axle?

IRS
C4 Corvette forward and upward
C5 Corvette forward and center
C6 Corvette forward and center
80's 911s forward and center
Ford GT forward and center

solid axle
94-94 B-body back and downward
3rdGen Camaro back and down
4thGen Camaro forward and center
5thGen Camaro forward and upward

Do they go in front of the hub or behind? And Why So?

The location is selected with suspension components and production line assembly procedures as the main criteria.

Does this play into the anti squat while braking?
Nope.

Does IRS differ than Solid axle?

Only that there may be more stuff attached to the upright, getting in the way of caliper location.


Some F1 cars have the caliper on the bottom center to lower the CG a bit.

BillL

Tad, not sure which car you're working on, but I had to position the rear calipers on my cars to give best clearance. The LCA brackets on the Fab 9 rear are different than the Currie rear. They were different enough that I had to place the calipers where I could connect the parking brake cables. Even though I've only driven the Chevelle a little bit, I didn't notice any difference in braking ability. My guess is, there's no performance advantage related to placement.

The El Camino:
http://i263.photobucket.com/albums/ii131/hlumpp/Misc%20stuff/DSC01105.jpg

The Chevelle:
http://i263.photobucket.com/albums/ii131/hlumpp/Misc%20stuff/DSC08550.jpg

short answer for me is to the rear for clearance.

im running the c6 z06 stuff, and to gain clearance im going to the rear. it had about 1/4" more without modification, and i made about another 3/8" clearance. all this, plus another 2" will then go into the lip of the wheel to offset the 1.4" that the calipers push the spokes out.

also, my setup with pb would need a creative bracket to pull the parking brake cable towards the back of the car if i had mounted them on the front. as mounted, the pb is in line with the handle.

Makes no difference at all. Put them wherever they fit, as long as the bleeder points up. :)

i have rear disc. and i have one caliper in the rear of the hub and the other is front of the hub.

Makes no difference at all. Put them wherever they fit, as long as the bleeder points up. :)

Yep, put them wherever you can for clearance with the bleeder facing up. However, the lower you put them the better the CG is, just make sure they can drain and shed debris. Putting them all the way at the bottom 6 o'clock position might let water & debris collect in them depending on the design & shape of the caliper.

Since they're bolted to the axle flange, the resultant torque exerted on the rear axle assembly during braking will always be the same.