Physics Matching a real life tire to AC tire

TrailSlide · May 1, 2018

I'm modeling my reallife track car in AC, and the real life tire compound is somewhere between the AC Semislick and the AC Trofeo Medium Slick. The tire is a 255/40/17.

I have real life AIM data at a track that also exist in AC. Assuming my vehicle model and track model is reasonably accurate. Is there anyway i can adjust some global lateral/longitudinal grip factor in AC tire model? and use telemetry to match the tire compound to the real tire?

So basically we ave
a car that's modeled in AC
a track that modeled in AC
telemetry data from AIM in AC and real life

I was thinking to adjust the lateral/longitudinal grip factor in AC tire model and then compare the telemetry log for Lateral & Long. G trace in AIM. and repeat until it matches up.

So what should I adjust in the AC tire.ini? should i just adjust the following only?
DX_REF is the longitudinal friction coefficient at a load of FZ0.
DY_REF same but lateral friction.

yes i know this method won't model the nuance of the tire perfectly, but I think as a home user's attempt in modeling a car, it's more than enough.

ALB123 · May 2, 2018

You've already answered your own question. All of the parameters pertaining to tires in Assetto Corsa are within the tyres.ini file and the corresponding LUT's they reference from within tyres.ini... If there are any other parameters related to tyres, we do not have a way to get to them. It's going to take a lot of trial and error. Trying to match the grip of your real-world tire is going to be hard enough...but don't forget about the Thermal Properties of the tires. How they heat up and cool down and spread that heat throughout the tires is equally important.

I'm sure someone knows a much better way to achieve your goal, but this is the extent of my tire modding knowledge. Even the lead developer of AC, Stefano Casillo, refers to tire creation as a "black art". I'm sure you've already discovered why.

If I were you, I would hop on over to the Assetto Corsa official forums and check out the pinned conversations regarding AC tires. Good luck!

Leonardo Ratafiá · May 4, 2018

I would use any kunos tire that feels similar to the real car, check if there are any tires with the same size and measures available on any kunos car and use that, they already did the job and very well. you can match your tires with content manager with the closest available (this is not ilegal talk I guess)

garyjpaterson · May 4, 2018

Leonardo Ratafiá said:
I would use any kunos tire that feels similar to the real car, check if there are any tires with the same size and measures available on any kunos car and use that, they already did the job and very well. you can match your tires with content manager with the closest available (this is not ilegal talk I guess)

I would also suggest that weight is a larger factor than just dimensions - pick tyres built for a heavier car and stick them to your more lightweight mod and grip will be super high, as its not operating at the loads designed (with the load sensitivity the coefficient will reduce with load, so if your peak loads are lower than the car you borrowed from then it won't really be an appropriate tyre without some modification).

Shigeno427 · May 6, 2018

I'm not sure DX_REF and DY_REF are the ones to be changing.

I've been attempting to learn a bit more about road tyres in the game and what the various values mean, and having been looking at a range of Kunos cars, all with 19 / 20 inch wheels, tyre widths ranging from 245 to 305, and modelled on cars with Pilot Sport 2, Pilot Super Sport, Pirelli P Zero, Continental ContiSport 5P, Dunlop Sport Maxx, DX_REF and DY_REF are the same for all of them, DX_REF is 1.26 and DY_REF is 1.23.

There are actually a lot of values that are very consistent across this quite wide array of tyres so you could probably find some sensible values for a lot of the tyre parameters if you looked at a selection of similar tyres in game.

Once you've got those more 'standard' values in, I'd suggest you can then concentrate on cars with offset wheel widths, as you can then begin to get a feel for which parameters correspond to more grip, as you're largely looking at the same tyre just wider on the rear (although likely with a corresponding slight increase in sidewall profile)

You can look in to what effects sidewall stiffness for example by comparing cars with run flat tyres to those without but on similar compounds (for example the C7 has Pilot Super Sport run flats as OEM, so I assume this is what was modelled, whereas the M4 has Pilot Super Sports that aren't run flats...).

I'm going to keep looking in to this and try to get a better understanding. From what I've been finding it appears Kunos model the highest performance tyre option available for whatever car they're modelling (I'm only looking at the 'Street' tyre option for each model), so for example on the 991 911 Carrera S, they modelled the optional 'ultra high performance' tyre set, which includes 305 rears.