Monday, February 6, 2012

Brake Caliper Placement - Ask Rob About Cars

Why is it that the rear calipers are in front of the axle and the front calipers to the rear of the axle?

-Augie Ruberto, Campbell, CA.

Great question Augie! There are multiple reasons for this. For most cars, it’s a non-issue. But if you look at sports cars, it’s almost always the rule with two notable exceptions I know of. Regarding the fronts, one reason is the steering knuckle is many times designed in front of the axle and so the caliper behind the axle offsets the weight and effect of the forces acting on the steering.
Another reason is for brake cooling. Ducts are used to direct cooling air to the brakes and a large caliper will block airflow to the disc which is vented. Cooling isn’t as critical for the rear brakes and it makes sense for weight distribution between the axles.
The two exceptions that come to mind are the Mitsubishi Lancer Evolution and the Nissan 370Z. I haven’t heard of any issues with the Mitsubishi, but the Nissan 370Z had a notorious brake failure when Car & Driver magazine was conducting one of their “Lightning Lap” tests. Further investigating with upgraded pads and then brake fluid to reduce temperatures, their suspicion was compromised aerodynamics. If you notice in the accompanying pictures, the front caliper is in front of the axle.

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