Det. Mickylaren

(1) How many pistons do the front brakes in the B8 A4 have?

(2) What determines where a manufacturer positions the calipers (i.e., closer to the front or rear of the car)?

The trend seems to be that performance-oriented cars have the calipers closer to the center (i.e., toward the rear on the front brakes, and toward the front on the rear brakes).

Check it out: (nearly?) all Toyotas have calipers on the front side of the front brakes, and (nearly?) all BMWs have calipers on the rear side of the front brakes. (And then there's the B8 A4, with its slightly-elevated-but-still-center-facing rear calipers.) I always assumed center-mounted calipers move some weight ever-so-slightly toward the center of the car. But surely there's a reason why they all don't do it the same way.

jagtoes

Modern Audi's have twin piston floating calipers on the front and single piston floating calipers in the rear. The location of the caliper is determined by the design of the suspension system. Due to the excessive torque when braking the mounting points are determined by the strongest part of the suspension. There is no rotational forces that I know of that would determine if a 3 o'clock vs a 9 o'clock is better. If you look at both super cars and race cars they are mounted in different locations but performance wise they both serve the purpose.

gunsmoker

The B8 has a single floating piston in all corners, but yes, it's not modern anymore.
While I don't know that for sure, I do suspect that the brands that care about weight distribution never put the front calipers ahead of the hub for weight distribution reasons.
Ideally, it should be as low as possible, but it's not safe to have brake hoses this low where they can get damaged more easily.

Det. Mickylaren

Hm. What's the verdict... 1 or 2 pistons for the front brakes?

jagtoes

It is a single piston caliper if it is OEM.