Location (and color) of Calipers are Up to Designers

Dear Car Talk:

I'm curious about the location of disc brakes vis-a-vis the wheel. I've seen the caliper housing mounted on top of the wheel, in front of the wheel, and to the rear of the wheel. What determines the placement of the disc brakes? -- Josh

Probably the mood of the engineer that day.

You notice their placement these days because they're often painted bright colors on expensive cars now. Some high-end models even let you choose your caliper color when you order the car. "I'll take the black interior and the chartreuse calipers, please."

Anyway, the job of the caliper is to squeeze the brake pads around the spinning rotor. That's what creates friction and slows the car. The caliper has to remain stationary, so it's bolted to the car's steering knuckle. The steering knuckle is the contraption that holds the wheel on the car while simultaneously allowing you to steer.

Depending on the design of the suspension, the caliper is usually placed where there's room for it. It can be mounted toward the front of the wheel or the rear. It can also be moved toward the top, although putting it at the top of the wheel would interfere with the strut assembly, so I don't think I've ever seen one there.

You don't want it underneath the wheel, because that would require extending the steering knuckle down closer to the ground, where it can easily get damaged. And besides, you've got plenty of other good options.

Ultimately, where it's placed really makes no difference to how well the car stops -- as long as it stays put. So, it's really an engineering and design decision based on where it fits best on a particular car.

In that sense, calipers are a lot like the watermelon you just bought vis-a-vis the fridge. It goes wherever you can fit it, Josh.

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