Rear Caliper Position - Any Advantages?

[DeltaT]

I am building up a 9" rear, and since I'm welding on the brake brackets, I have some latitude on how I position the rear calipers - right at 90 degrees, slightly higher, etc.

For example, this guy has his clocked slightly higher than the centerline:



And this guy's is slightly lower:



And most pictures I see, where the caliper is behind the axle line, the caliper is clocked right at 90 degrees.

Are there any advantages to clocking the calipers other than the standard 90 degrees, other than modest packaging considerations? Clearly I would get into bleeding issues if I went too far either direction.

Thanks,

Jim

[realcoray]

I think any benefit of position would be small. For example, putting them lower, moves the mass slightly lower, and probably gives them more airflow over the caliper but you aren't going to notice anything as a result.

[dontlifttoshift]

The second picture is my rear end. The calipers arent actually mounted that low, they are just hanging there at that point, they actually ended up near vertical, in other words the bleeders are pointed straight up.

I have looked into this a little, and found no evidence supporting one position to be better than the other, in front of or behind the axle, or clocking the caliper either. Even with the caliper mounted horizontal, they can be bled by removing the caliper, installing a shim to simulate the rotor and bleeding normally holding the caliper in your hand......that is a pain in the arse, though.

Mount the calipers in a way that gives you the best clearance and easiest maintanence. After that I try to match the clocking of the front caliper for aesthetic purposes.

[DeltaT]

Thanks, guys.

Jim

[Bryce]

I always wonder about the reaction load on the car.

[dontlifttoshift]

Bryce, can you elaborate?

In side view, the caliper will load the axle housing through the caliper mounts trying to rotate the pinion down, that won't change. Would there be a different reaction between the caliper mounted front or rear?

[realcoray]

I'd suggest looking at where OEMs or competition racing cars put their brakes. The assumption is that those people spend millions of dollars looking at these sorts of questions.

For the C6R and Stingray for example, GM has the brakes in front. On F1 cars though it appears like they are very low in the back.

Some of these things may be packaging issues, the F1 car for example has a lot stuff going on around the caliper, but you have to assume that their goal is to maximize everything to reach peak performance with their very light weight, high horsepower cars. Shifting of grams lower means more to them than it does on a production corvette or even for the C6R.

Again, it's pretty much not going to make any difference, but this is the approach that I will often take when considering something like this.

[Sieg]

Koenigsegg Agera R rear calipers are at 3 & 9 o'clock behind the axle. Their engineering is probably some of the more current and advanced.

Porche's Carrara GT had the rear calipers slightly lower than 3 & 9 o'clock in front of the axle.

Then you'll see some F1 cars with bottom mounted calipers.



What is best and how much influence does it have relative to the desired performance objective?

[intocarss]

Here's some discussion about it

http://fsae.com/eve/forums/a/tpc/f/1.../m/80310023931

[dontlifttoshift]

Good Link!!