A car's brakes are designed to create friction in a bid to slow down and stop a vehicle by scrubbing away all its momentum and inertia. For that reason, brakes tend to get pretty hot, including the brake calipers. If you're driving hard, such as constantly using the brakes at a race track, the calipers could heat up to 500 degrees Fahrenheit. Or, about 250 degrees Celsius. This is considered very hot for brake calipers. On the other hand, brake calipers won't usually go beyond 250 degrees Fahrenheit when you're just driving around normally. As it reaches into the 300+ and 400+ degrees Fahrenheit mark, your brake calipers are getting toasty, and good ventilation is a must to cool them down. Anything above 500+ degrees Celsius would require a check-up afterward for any damage.