Caliper Placement

[Zilli]

Hi All,

I was flicking through a Unique Cars mag on the flight home tonight and i noticed that some cars have their calipers on the front side of the front caliper, and some have it on the rear, ie when you are looking at the wheel, it's on the right or the left hand side of the disk... the exotics seem to have it on the right...

any ineherent advantages or reasons why they would do this?

[aaronng]

Space. If you have suspension components protruding out at the rear of the disc which doesn't give enough space during full lock, then they put the caliper at the front.

[Zilli]

so thats the only reason?

[T-onedc2]

I've always noticed exotics plac the caliper rearward, I thought for the slight diference in weight bias, but even Porsche do this and they're RR and AWD layout.

[Black_DC5_R]

With a rear placed caliper, the disk has to try to lift the car's weight under braking, which also helps the friction and braking force.

Placing them forward pulls the cars weight down, with the direction of travel of the disk/rotor. This also pulls the cars nose down under braking more than an identical setup with a rear caliper.

[aaronng]

With a rear placed caliper, the disk has to try to lift the car's weight under braking, which also helps the friction and braking force.

Placing them forward pulls the cars weight down, with the direction of travel of the disk/rotor. This also pulls the cars nose down under braking more than an identical setup with a rear caliper.

Caliper placement does not dictate whether it pulls the car's weight up or down. That depends on weight shift, and during braking, the car's weight is shifted to the front, hence the nose dives during hard braking.

[Zilli]

Caliper placement does not dictate whether it pulls the car's weight up or down. That depends on weight shift, and during braking, the car's weight is shifted to the front, hence the nose dives during hard braking.

hmmmm i can kind asee what he is saying though, the physics of the caliper stopping the disk from both sides, but at the end of it it's all going to result in a nose dive like you said Aaron

[Ivza]

the Mercedes S-Guard has 2 calipers per wheel (front 2 only i think)

imagine the stopping distance on that thing !

[trism]

the Mercedes S-Guard has 2 calipers per wheel (front 2 only i think)

imagine the stopping distance on that thing !

the stopping distance on a car is not jsut related to the brakes but how good the tyres are.

no point having 2 calipers, with a total of 18 pistons when youre running $89 dollar rubber all round. youre just gonna lockup and slide like a mother

a car with fully slick tyres and stock brakes will pull up quicker. only once but lol, coz the temp/brake fade would be nutso

[Black_DC5_R]

Caliper placement does not dictate whether it pulls the car's weight up or down. That depends on weight shift, and during braking, the car's weight is shifted to the front, hence the nose dives during hard braking.



Its a no-brainer saying that the car will shift forward and nose dive under braking. The momentum of the vehicle and the weight shifting onto the front suspension is what causes this dive.

Placing the caliper on the rear side of the disk/rotor is to counteract this shift in weight and to oppose the rotation of the rotor, whereas the caliper on the forward side of the rotor allows the vehicles weight to be pulled downwards even more.


If you are still having trouble grasping this concept, get a CD and rotate it like a brake rotor. Now with your free hand, use it as a caliper which is grabbing the rotor slowing it down. On the rearward side it pulls your hand upwards and on the forward side it pulls your hand downwards.

[JohnL]

Its a no-brainer saying that the car will shift forward and nose dive under braking. The momentum of the vehicle and the weight shifting onto the front suspension is what causes this dive.

Forward weight transfer under brakes is identical in principle to lateral weight transfer under cornering. For X acceleration strength (any 'G force' being an 'acceleration') the degree of forward weight transfer is dictated by the wheelbase length and the CG height (for lateral WT the dictates are track width and CG height).

As with lateral WT, the weight transfers through two different vectors, i.e. through the 'elastic' vector of the springs (and dampers), and through the 'geometric' vector defined by the design of the suspension geometry.

WT that occurs through the 'geometric' vector occurs instantaneously and involves zero 'dive' motion (or roll motion for lateral WT). If the 'pitch centre' (the point around which any forward pitch would be centered, the same thing as a 'roll centre' for lateral roll) were at the same height as the CG then no pitch motion under brakes would occur no matter how soft or stiff the springs may be, though forward WT would still exist despite the front springs not compressing / rear springs decompressing.

WT that occurs through the 'elastic' vector occurs over time (i.e. a short time period), and does involve "dive" ('pitch') motion (or 'roll' motion for lateral WT). If the 'pitch centre' were at ground level then all weight transfer would occur through the springs and dampers and forward pitch would be considerable unless the springs were quite stiff. The softer the springs the more slowly weight will transfer through the springs.

The degrees of 'elastic' and 'geometric' roll stiffness vectors are determined by the location of the geometric roll centre (suspension design), the stiffness of the springs (and dampers), and the strength of the acceleration. The ratio of elastic and geometric vector strength existing at any given moment (in a given suspension at one end of the car) are not fixed, but are constantly changing from moment to moment depending on the strength of the lateral acceleration

This is all hugely complex theory that lies at the very heart of chassis dynamics, a lifetime's study...


Placing the caliper on the rear side of the disk/rotor is to counteract this shift in weight and to oppose the rotation of the rotor, whereas the caliper on the forward side of the rotor allows the vehicles weight to be pulled downwards even more.

No, the location of the caliper has zero influence on dynamic weight transfer (in any way you might want to consider this).

All that placing the front caliper behind the hub centre does (or in front of the hub on the rear brakes) is to place more static weight nearer the centre of chassis mass, i.e. to a slight degree improves the 'polar moment of inertia'. This assists (slightly) to improve steering and handling response, the reason why racing cars try to keep all masses (as far as possible) near the centre of the chassis.


If you are still having trouble grasping this concept, get a CD and rotate it like a brake rotor. Now with your free hand, use it as a caliper which is grabbing the rotor slowing it down. On the rearward side it pulls your hand upwards and on the forward side it pulls your hand downwards.

This analogy is highly flawed. Regardless of caliper location all it does is try to rotate the chassis mass around the hub centre, and this will always try to 'lift' the rear of the chassis / 'lower' the front, regardless of where the caliper is located relative to the rotor.