It is brakes on many trucks. A larger rotor means that less brake friction is needed to stop the car. Trucks that used to take 15" tires now take 16-17" tires to fit the brakes.
Over 17" on a 1/2 ton to 1 ton truck (or ~16" on a smaller vehicle) is probbaly for either looks or handling (shorter sidewall = less sidewall flex and a "tighter feeling" vehicle). Aaron Z
Yes, I have seen the argument. Yes, I understand basic physics. No, I don't buy it.
Trucks are not any bigger than they were before. And, they don't weigh as much as they did before.
No modern, consumer grade truck I know of, and I worked on everything for 35 years, ever had an issue with brakes.
Nothing stopped the manufacturers from putting bigger wheels, and bigger brakes on them back then. In fact, they did put bigger wheels on the on the heavy duty 3/4 ton, and the one tons, on the rest, the manufacturers chose not to.
A full size conversion van, full of gear, with a family inside, was a very heavy vehicle. 15" wheels, and they stopped just fine.
We had a 1983 or so, F100 at work. I used to fill it with 3500lbs of gravel when I was doing my driveway. It stopped just fine too.
Sorry, doing it now to reduce weight, is the only thing that makes sense to me.