Two cars , CAR A (light car at 3000lbs) vs Car B (heavy car 500lbs heavier at 3500lbs). They get the point that of the exact same initial braking point, the two cars with the same 400HP are running:

car A 120mph (53.64 m/s)
car B 114mph (50.9 m/s)

the simple part of this example is that we can just plug in the numbers if we agree that the heavy car will slow at 8% less deceleration rate. we will call this 1g vs .92g respectively. this is because of the changing of the mu for the tires as weight is added to them. (weight on the tire, is the total weight/4 plus weight transfer weight/2 based on deceleration rate)

This means in 4 seconds the light car slows to 33mph (15m/s)
this also means in 4 seconds, the HEAVY car slows to the same speed

keeping it really simple. the KE at the start is:
1,991956 J Light
2,085,914 J Heavy

the KE at the end at the final same exact speed is:
153,405 J light
178,977 J heavy

this ends up with the lighter car dissipating a total of 1,838,551 for the light car
and 1,906,937 J for the Heavy car. heavy car dissipates more energy by 3.7%
not anywhere near the increase that the 15% increase of weight would first indicate

So,

Because the lighter car slows to the same speed in 4 seconds (3.94secs) and the heavy car slows to this same speed in 4 seconds too the RATE OF KE DISSIPATION is HIGHER for the heavy car by about 2%. no surprise here

625HP/sec for the light car ( example : 1,838,551 J /4 sec (3.94actual) /746watt =hp/sec)
639HP/sec for the heavy car ( example : 1,906,937 J /4 sec /746watt =hp/sec)
(only about 10hp/sec greater dissipation rate)


BUT, since we know the turn in point will happen at a slightly lower speed for the heavy car (13.5ms or 30mph), the result is: . Because now we are slowing at the same rate of .92g but for 4.15 seconds. NET NET 626hp ave dissipation rate....... the heavier car has the same of KE dissipation as the light car

The heavy car:
2,085,914 J at 50.64/s (114mph)
144,971 J at 13.5m/s (30mph)
Total KE dissipated of 1,940,942. / 4.15 seconds = 626hp ave dissipation

The rate of heat dissipation for the HEAVIER CAR is the same vs the light car for its decel rate and its lower top speed at the moment of braking (at the same spot on the track) and slightly lower target speed upon brake release for turn in.

the interesting thing here is also, with both cars activating their brakes at the same point, they end up at the same spot before turn in, 320f vs 316ft, if you use the decel rates of 1g vs .92g .

Therefore, this shows that adding weight, under these normal conditions, actually doesn't change the burden on the braking system.