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Discussion Starter #1
I was asked a question today about car brakes and I don't know the answer, so I was wondering whether anyone here could help.

On front wheel drive cars the brake caliper is fitted so that it is at the front relative to the wheel centre line.


On rear wheel drive cars it is fitted to the rear relative to the wheel centre line.

Why is this?
 

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I have absolutely no idea but now that you've asked I really want to know.
 

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I'm going to make a wild stab:

Steering gets in the way on FWD
cars so the calipers are at the front.

Otherwise they'd be at the rear too
like the rear ones.
 

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Discussion Starter #4
I'm going to make a wild stab:

Steering gets in the way on FWD
cars so the calipers are at the front.

Otherwise they'd be at the rear too
like the rear ones.
Shouldn't make any difference with the steering I wouldn't have thought?

The only things I can think of are torque reactions due to the driveshafts, or simply convention.

Rear wheel drive cars have always been like that, but the first front wheel drive cars (for some unknown reason) did it differently and they have stayed like it.

Four wheel drive cars seem to have them on the front of the disc as well.
 

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For braking effort it doesn't matter where they are in relation to the disc. In terms of handling it's better to have as much weight towards the centre and that's why high performance cars tend to have calipers rearmost at the front and forwards at the back. Front wheel drive cars tend to have them foremost so that they don't interfere with the drivetrain and steering as TT4N says.
 

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I'm not sure this can be a universal rule - the front calipers on the RWD GTV6 and the 75 are fitted in front of the wheel centre line. And just to be different, the rear calipers are virtually on top of the discs!
 

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It all sounds like it is down to what business is going on the other side of the hub.
I can't see it matters a jot where on the hub they are placed. I guess placed at the rear has gravity to help :lol: :lol:
 

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Only other thing I can think which might affect it is anti dive geometry under braking. So a caliper in front of the suspension upright at the front will tend to want to ride down the disc and push the front up under braking, counteracting the natural weight shift forwards. At the rear the opposite happens helping to keep the rear down. My old S3 XJ6 was supreme at keeping level under braking with the best anti dive I have ever experienced.

I may be talking balderdash.
 

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Only other thing I can think which might affect it is anti dive geometry under braking. So a caliper in front of the suspension upright at the front will tend to want to ride down the disc and push the front up under braking, counteracting the natural weight shift forwards. At the rear the opposite happens helping to keep the rear down. My old S3 XJ6 was supreme at keeping level under braking with the best anti dive I have ever experienced.

I may be talking balderdash.
The rotational forces will be the same in both configurations.
 

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Perhaps it could help with cooling as well in some instances?

Brakes placed at the rear of the wheel could benefit from airflows coming from the underside of the body and ducting, as well as the outside. The open aprons on the front of cars tend to have fancy aero mouldings that cause the flow of air to go into the engine and brakes much more efficiently. By putting the brakes behind the hub, the air that is flowing at higher speed will have much better flow towards the rear of an alloy wheel than the front; as the front of the wheel will remove the energy from the air. It also means that such ducting could have more shallow angles from front inlet to rear outlet, making for less forward resistance?
 

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I was asked a question today about car brakes and I don't know the answer, so I was wondering whether anyone here could help.

On front wheel drive cars the brake caliper is fitted so that it is at the front relative to the wheel centre line.


On rear wheel drive cars it is fitted to the rear relative to the wheel centre line.

Why is this?
it's not always like that...

but to answer your question: on fwd cars the steering rack connectsot therear of the upright, so there's moreroom on the front for thecaliper. This is reversed for rwd cars.
 

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Discussion Starter #14
it's not always like that...

but to answer your question: on fwd cars the steering rack connectsot therear of the upright, so there's moreroom on the front for thecaliper. This is reversed for rwd cars.
Not in all cases, many rear wheel drive cars have the steering connected at the rear of the upright as well as having the caliper at the rear.

A good example is the E39 BMW. 6 cylinder cars had rack and pinion with the rack and arms at the back. 8 cylinder models had a steering box and the steering arms connected at the front of the hub.
 

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I was asked a question today about car brakes and I don't know the answer, so I was wondering whether anyone here could help.

On front wheel drive cars the brake caliper is fitted so that it is at the front relative to the wheel centre line.


On rear wheel drive cars it is fitted to the rear relative to the wheel centre line.

Why is this?
No idea what the answer is, but that's an excellent question.

I wonder whether each car manufacturer - per model - can explain why. So what set up may work on a fwd Golf, may not work on a fwd Passat, for whatever reason (cooling, engineering, manufacturing, serviceability). Dunno, just guessing.
 

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Not in all cases, many rear wheel drive cars have the steering connected at the rear of the upright as well as having the caliper at the rear.

A good example is the E39 BMW. 6 cylinder cars had rack and pinion with the rack and arms at the back. 8 cylinder models had a steering box and the steering arms connected at the front of the hub.
hence the "it's not always like that"...

Hyundai i40 (fwd) currently has the brake calipers on the front side, but tests are underway in spain and norway (or sweden, someplace cold anyway) with the caliper moved to the back. they have a brake judder issue that hopefully will be solved by doing this... people with complaints will get yhis retrofitted.

so, whatever side is convenient to the manufacturer.
 
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