We are seeing more and more car enthusiasts go to extremes to make their rides look good by adding really large brake packages from German imports to fit them on their Subarus and Hondas. I guess it looks cool, but are they actually functional or safe?
Upgrading brakes on Honda Civics to Type-R calipers and rotors or bolting up the bigger 300ZX brakes to S13s and S14s can be affordable and effective for enthusiasts. But bolting on excessively large multi-piston calipers and rotors off high-end sports cars like Porsche and Ferrari to bolt-on your Subaru may look cool in the parking lot but to do it right, you need a lot more than just adding larger-diameter rotors and increasing the number of pistons in your calipers.
The first biggest issue to consider is is it safe? The common misconception is that you can add any caliper and rotor to any car as long as it fits. This is false, false, and false. There are big differences in braking performance and what may seem like a good idea could actually give you less stopping power. Take a Subaru WRX, for example, they have 30 percent more brake piston area than a Porsche 911. So by convention wisdom, adding a 911 caliper to your WRX would give you 30 percent less brake torque and a significant (and very unsafe) shift of brake balance to the rear of the vehicle.
Rotor thickness, not just diameter, can impact performance and safety and must be considered when custom retrofitting brake parts not designed for your car. Calipers used on discs that are thinner than the OEM design can cause the brake pads to move past the abutment surfaces on the caliper, resulting in damage or brake failure. It is also possible that the pistons move completely past the seals in the caliper, resulting in complete and catastrophic brake failure.
Just like the rotors, the calipers are also designed for specific operating conditions, so bolting them up to an entirely different chassis can also be problematic, if not downright dangerous. The caliper bodies themselves are built to withstand the requirements of their intended application. Calipers can’t be used too far outside the of their OE design loads. This also holds with the ABS system,which only functions within the parameters of the original braking system.
The most important vehicle parameters are the gross weight, weight distribution, center of gravity, wheelbase, top speed and intended use, and tire size. Calculations are then performed in order to determine the best disc size for the application. Caliper piston area should closely maintain the original braking torque and fluid volumes. Companies that design performance brakes must verify optimum brake balance through the full range of deceleration rates and to ensure safety, performance and the integrity of the ABS system. Further calculations are made for the brake pad surface area and volume.
So the next time you think that bigger brakes would give your car better performance, think again. It may look cool in the parking lot, we can’t deny that.