Placement of disc brake calipers for best performance

[berkeman]

TL;DR Summary

Does the placement of the calipers make a difference for braking performance in sports cars?

I thought that there was a standard placement for disc brake calipers on the front and back wheel assemblies for high-performance sports cars. I thought that I usually saw them placed at the back of the front wheels and the front of the rear wheels, but lately I've seen the opposite and other placements.

On sportbike motorcycles, the caliper placement is usually dictated by the nearest strong structural element (like the front forks and the rear swingarm), but it would seem that in cars you would have a lot more flexibility in choosing where on the brake disc circumference to place the calipers.

I've tried a few times to figure out justifications for caliper placement (like anti-dive characteristics under braking), but I haven't been able to get very far. What are the reasons for choosing the various caliper placements for performance car brakes?

This is a snip from a Google Images search for disc brakes on sports cars:

 

[cjl]

So there's a very slight argument to be made for placing them at the back of the front wheels and the front of the back wheels, since that will (very minimally) reduce the polar moment of inertia of the car by moving weight closer to the middle. Beyond that though, it's likely determined mostly by where the best attachment point for the caliper is (which will depend on suspension geometry) and what the brake cooling solution is.

 

[Ranger Mike]

now tha tis a pretty good argument for polar moment consideration! In the real world the caliper placement is going to be a compromise with engine placement and steering component mountings. The biggest headache i faced was front or rear steer design. this is placement of the rack and pinion steering relative to room you have available on the chassis. The difference between a caliper mounted at 9 o'clock position vs 3 o'clock or 12 o'clock is pretty insignificant in the scheme of things like brake cooling ducts, interference with ARB mountings, control arm linkage etc...
the benefits of 9 vs 3 o'clock mounts will yield additional down force equal to that of a Georgia piss ant doing 20 push ups.

my opinion

 

[cjl]

Yeah, it is a very slight consideration in the overall scheme of things. Interestingly though, it does seem to be the favored configuration in nearly all modern mid engine high performance sports cars (I looked up the Cayman, 488, Huracan, R8, and C8 Corvette and they all put the front brake on the rear of the rotor and the rear brake on the front). I wonder if there's something else driving them towards that solution, or if it's just a case of trying to squeeze out every last fraction of a percent or something.

 

[Ranger Mike]

From strictly an engineering purist point of view, you want as much unsprung weight between the axle center lines. we are talking about maybe 20 lbs. but it all adds up! I remember cutting off all excess threads on every bolt! Cheap way to cut weight!

 

[Baluncore]

Stray objects on the road surface, and water and gravel thrown up from the road surface, pose a threat to brake system integrity. The best protected place for the calipers and brake hoses will be at the back of a front axle.

Where independent trailing arms reach back from under the body to the rear axle, the brake lines follow that arm to the caliper at the front of the hub. The trailing arm offers some protection to a caliper at the front of a rear wheel.

 

[Ranger Mike]

BAlun - question ...

small stones get wedged into the tire grooves. As the vehicle moves forward the debris is thrown off at velocity. Anyone who ever followed a pickup truck with monster tires knows to get away from it asap.
Stones are flipped to the rear of the car or carried up and ejected at any degree of tire rotation. Primarily the stones are spun off just after being picked up.
So your theory on limiting debris jamming the caliper would apply if the caliper was mounted at the 3 o,clock position. Right?

On the rear axle you still have rubber brake lines connecting to the caliber but they plumb into steel brake lines that run to the front master cylinder. I have not seen any brake lines mounted on the lower control arms. What make and model has this? Am curious and always willing to learn! Thank you, B.

 

[Baluncore]

What make and model has this? Am curious and always willing to learn!

The rear brake line usually separates forward of the rear axle. There it splits to the two sides of the vehicle, where it runs up and backwards to the flexible brake hose. The lines are above and follow, but are not attached to the trailing arms, except on a motorcycle swing arm. There is usually less vertical movement for the brake hose at the front of the rear axle than at the back.

It is not gravel in tread that is the problem. Don't minimise the problem of gravel in water on the road being thrown at the underside of the vehicle. It only takes one trapped rock to damage the brakes. Driving on dirt roads, crossing dips and creeks throws all sorts of things sideways at the brakes. Bull bars here are designed to push smaller animals, like sheep and kangaroos, downwards where they will tear out brake lines that are not well protected by the chassis, floor pan or a solid suspension member.

Sports cars are faster, lower and more delicate than the vehicles I drive, but the principles are the same, only the damage and cost with a sports car are greater after hitting a rabbit or hare.

 

[Ranger Mike]

Which is why the caliper would provide maximum protection if mounted on front side of any rotating wheel. The debris would have 180 degree to throw off before coming close to the front mounted caliper. My drive way of 30 years is gravel. am familiar with its effects. Modern disc brake design as the caliper buried inside the wide wheels on my Mercedes and would take a huge amount of crap to get to the pads thru the caliper. i just did brake job on it!

 

[Baluncore]

Which is why the caliper would provide maximum protection if mounted on front side of any rotating wheel. The debris would have 180 degree to throw off before coming close to the front mounted caliper.

Brake calipers today are well protected inside the wheel rims, but they sometimes have an open back to make it easier to change the pads without removing the caliper. That provides a path for grit ingress, especially when different rims are fitted.

I can't afford to drive my 450SE, the Isuzu truck and Toyota Land Cruiser are just too economical.

 

[256bits]

Summary: Does the placement of the calipers make a difference for braking performance in sports cars?

(like anti-dive characteristics under braking

Would that be it?
Front braking tends to lower the front (raise the rear ).
Putting the calipers on the advance side of the disk for the front wheels seems to me that the situation would be aggravated, with the braking torque driving the frame downwards.
Similar argument for rear braking.

 

[Baluncore]

At the rear, where an arm is hinged forward of the wheel, braking torque will tend to rotate the arm, lowering the fulcrum in front of the rear wheel.
The braking torque is applied to the arm on the axle, so it does not matter where on the disk the caliper is mounted. The length of the trailing arm from the fulcrum to the axle will be important.

What is the geometry of the front suspension? Does it have a similar effect or the opposite?

 

[Ranger Mike]

this should address ALL questions..

https://www.team-bhp.com/forum/tech...on-how-do-engineers-decide-its-placement.html