i wanted to say something about the tires vs the drivable width of the road in Forza games.
imagine the road is a gradient spreading outwardly from the center line. grip matters most down the center, but becomes less effective as you reach the edges of the gradient, which in this case is dirt, grass, and general uneven terrain. this commentary is about street races specifically, but also in a lot of road races. theres a simple mathematical way to evaluate the tire's overall performance across the gradient.
if we take the slick tire grip value as the constant and give it a value of 10, semislicks generally will be a 9.7, and rallies will be a 9.1.
our variables are the off-road number, and the lateral g's at 60mph. let's use a random car as an example, 65 Alfa giulia.
(offroad) x (lateral g's) x (grip as a percentage of 1.0) is our formula, scaling the number to the smallest comparable factor.
slick tires (5.7) x (1.07) = 6.099 x (1.00) grip =
6.099 rating @ 483pi
semislicks (5.8) x (1.07) = 6.206 x (0.97) grip =
6.020 rating @ 474pi
rallies (6.9) x (1.03) = 7.107 x (0.91) grip =
6.467 rating @ 454pi
what you see with semis and slicks is the exact same g value, almost without fail. and the grip difference is 3%, which can immediately be recouped from the surface area of extra rear tire width. meaning your pi savings is 9 on a virtually identical tire. here the decision becomes more abstract, sprint vs circuit, race vs rivals, how good the surface is, and how good your racing lines are. 9pi can be huge in the right circumstances, but it's close.
the difference in rallies vs semislicks performance over the gradient is much larger, at about 7%. but at a savings of 29pi the decision at this point is pretty simple, because you're already getting a better overall tire relative to the diminishing outward grip on the road, with room for upgrades.
visually speaking, rallies start with less grip on the y axis but lose grip on a much slower deceleration curve on the x axis, and it steadies out at a higher rate. it's effectively performance compression, but it's wide-band compression which gives you high pi savings.
in the specific example of the Alfa, your savings of 29pi on rallies can allow for race weight reduction and a base cent upgrade for 30pi, and the lateral g's actually increase from 1.03 to 1.04, whereas the slicks would still only be a 1.07. you're sacrificing marginal handling to bring your power/weight from .07 to .09, or +23%
there's obviously a million other factors once you start to build, but this is the closest comparison you can make on just the tires.
anyway this is all obvious stuff to good players, but i've never seen anyone attempt to quantify it, so I thought I'd go for it while I'm feeling chatty.
