Brake heating is not a real issue with emergency braking, only with frequent braking which race cars do. That's why "upgrading" to "big brake" systems on passe

Brake heating is not a real issue with emergency braking, only with frequent braking which race cars do. That's why "upgrading" to "big brake" systems on passenger cars is usually a waste of money and reduces performance: unless you're driving on a track where you have to brake a lot, and the cumulative braking keeps the brakes hot, you're not helping. Even worse, the brake pad compounds used for race cars are different, and are designed to maintain performance even when very hot, whereas passenger car brakes have to have great performance when cold. The bottom line is: a single panic stop on the highway isn't limited by your brakes on a passenger car, it's limited by your tires. The more friction your tires have with the road, the faster you'll slow down. So yes, if you want a 40 ton truck to stop faster, it's completely doable: just increase the amount of rubber in contact with the road. Adding more wheels will do that quickly. However, more tires means more rolling friction which means less fuel economy and fuel economy is critically important to long-haul trucking. Also, adding more axles causes maneuverability problems in the city. Notice that on standard trailers, the rear axle set can be moved forward and back. They set them in the rearward position for long hauls, and in the forward position for shorter hauls.