Take the weighted average of each of your vehicles’ drive types (and torque splits F/R for AWD vehicles) and express it as an overall percentage F/R.
For sake of simple calculations, we can calculate the weighted average of ONLY the % of torque to the rear wheels of each vehicle. After taking the weighted average, we can just subtract the %RWD from 100% to get the %FWD.
For example, say you have 2 RWD cars, one FWD car, and a 40/60 split AWD car. (2 * 100% + 1 * 0% + 1 * 60%) / 4 vehicles = 65%, or a 35/65 F/R torque bias.
Go wild & have fun, Oppo, as bikes & drones & pets count too!