Leading edge / Trailing edge calipers
 

So I've been looking around, and noticed a few things about calipers.

On some cars, I have noticed that the front calipers are sit/work on the leading edge of the disk, and on others they work on the trailing edge. The same applies to the rears. Different cars have them both front and back leading, sometimes front leading, back trailing.

What gives?

Does this effect braking efficiency?
Is one better than the other?

Any thoughts, inputs guys?

Thanks Jakes

I don't think it matters. More of a packaging issue than anything else and what works best for the manufacturer. The cars that are looking to lower their CG's as much as possible put the caliper at 6 o'clock. F1 cars come to mind.

Not an expert but here are my thoughts....

You want the weight low so top is out. The bottom will get you into trouble with debris so that only leaves leading or trailing sides.

The 2 thoughts that come to mind are weight distribution (for the total car) and airflow.

Seems obvious why the older 911s have the leading edge for weight distribution alone.

On the leading edge and the caliper is in the cool (relatively) air. On the trailing edge and the air has passed over the hot rotor and has been warmed.

With the caliper on the leading edge...when the clamping effect of the caliper is transmitted to the strut...the force is in the down direction on the strut.
The opposite for the trailing caliper.
Now this is just physics...it does not do a lot of forcing....the amount of force would depend on the speed and gripping power of the caliper.
On a lightweight race car (such as formula Ford) it does make a difference in the setting up for a corner.
With more weight being transferred to the tire entering a corner, the driver will set up for that corner differently.
Not that either way is wrong...the car just feels different.
It would be a great comparison for Jack perhaps to see which method would improve the lap times.
Sorry Jack....more work for you LOL!
Bob

I think calipers are mounted on the trailing edge on the rear of a 911 to keep the caliper from getting in the way of the suspension/spring plate bolts.
-Chris

Very interesting, more than I thought. I would not have thought that the difference in placement would/could affect the weight distribution that much, but at the end of the day I suppose 'Every little helps.

Thanks Jakes

At the prompting of a friend, I checked the rear calipers on my 911 and they are leading edge mounted and they don't seem to interfere with the suspension bolts. I don't know where I got that idea...
-Chris

Leading or trailing edge lets the caliper manufacturer know where to put the smaller piston. We're talking multi piston solid mounted calipers. The smaller piston goes toward the trailing side. As the caliper clamps onto the rotor it drives the leading edge of the pad in a wedge type fashion. The smaller piston has a higher force on it than the larger leading piston. This helps keep the brake force even across the pad and helps eliminate pad taper which is common with multi piston calipes of old.

911 have f/r calipers mounted in the leading position.
930 have the fronts in leading, rears in trailing
996/997 have trailing mount front and leading mount rear

most of the time the choice is determined by packaging constraints, you have to avoid steering and suspension arms when figuring out where to place the calipers.

there is a slight advantage to trailing mount on the steering wheels, as it reduces the turning moment a bit.

Yes, there is an advantage to a trailing-edge front and leading-edge rear. It moves the weight towards the center of gravity. Look at any scratch-built race chassis.
I had my choice with my 77 and decided to follow my race engineer son's advice. (leading edge in rear.)
Bill K
http://forums.pelicanparts.com/uploa...1304625742.jpg

yes, it does that too and on th trailing arm it reduces the energy required to move the arm up and down.


These are all small advantages