Brake caliper position?

[IroningMan]

8bit said:

GuitarTech said:

thanks all for the answers so far. So it has no effect on suspension dive under braking? I'm thinking about the effect of newtons second law here? Or is it irrelevant?

Just checked with my more mechanically-learned friend, he's confirmed that - if the front calipers are at the rear of the disc then there will be less dive under braking than if they were at the front.

He's also said that normally FWD cars have the front calipers at the front, to do with packaging (clearing drive shafts etc. I guess) and cooling. RWD cars tend to place front calipers at the rear of the disc. I've got one FWD car and one RWD car and they follow this convention.

FWD cars generally have the steering rack mounted behind the sump and gearbox, so have the steering arms and trackrods at the rear of the hub and the brake calipers at the front.

RWD cars generally have the steering rack mounted ahead of the sump, so have the steering arms and trackrods at the front of the hub and the brake calipers at the back.

As an aside, the RWD rack position puts the more heavily loaded (outside) steering arm in tension, whereas the FWD configuration puts it in compression, which can be less desirable.

[Mike600F]

DoubleD said:

Have you spent the past 4 years thinking about this?

Haha! In a strange way, yes. Been building racecars that long so I'm always mulling stuff over. Happened upon the thread through google and remembered thinking the same thing, so thought I'd give my 2 cents.

8bit said:

Mike600F said:

Lots of interesting stuff.

Thanks for the post! Nice to have some genuinely informed input.

No problem!

Max_Torque said:

it also affects wheel bearing loads as brake torque reaction can either add too, or subtract from the normal force carried by those bearings.....

I can see that. Putting the calipers towards the back would increase the bearing load at the bottom. Vice Versa for putting them forward.

IroningMan said:

As an aside, the RWD rack position puts the more heavily loaded (outside) steering arm in tension, whereas the FWD configuration puts it in compression, which can be less desirable.

You also get more clearance between the wheel rim and steering rack tie rod in the forward position as the outside wheel turns less than the inside (look up the ackermann phenomenon anyone who can't see this). Generally you can then use up this extra clearance, moving the rack and tie rods forward further and eliminating a little compliance in the process. You are moving weight forward though (Polar moment of inertia again!) when compared to having the rack in the rearward position, so it's a trade-off - depends where your priorities are....