Uping size of Brake disks = red color = less braking...?

Hi Devs....just a question - I was working on a new car based on the new 70s mini car body and just noticed that when I UP the size of the brake disks (more stopping power 0 it has single-piston solid disks on the front and drums on the rear atm), the color goes red as if the bigger brakes are making my braking WORSE....is there a bug here maybe, or is there something with the calculations which is making my braking worse (more weight for example) that I am not understanding?
Thanks!
Thanks!
