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Tire Load Rating Calculations - In-Game Vs Reality


#1

I’ve begun to notice that the tire load ratings being calculated in-game are not really in line with tires in the real world, with Automation ending up quite a bit on the low side of things. I’ve knocked together a small spreadsheet to show some of the differences I’ve found:

Note that the calculated load rating does not change with the speed rating of the tire, nor the type of tire compound, or the quality slider either, for that matter - it is, as far as I can tell, solely a function of tire diameter and aspect ratio. And as you can see, low-profile tires, which are becoming far more common these days, seem to have a fairly significant discrepancy compared to higher-profile tires.

For example, the 235/75R15 tire, which was a fairly common light truck tire back in the 80s and 90s, has a rated load of 1984-2094 kilos per tire per the Automation calculation, vs 2039-2271 kilos per tire from real-world examples, which is about 90 percent of what the real-world tires can handle. The 295/35R19 tire, which is standard rear fitment on a Porsche 991, has a rated load of 1235-1433 kilos per tire in Automation, versus 1764-1984 kilos per tire in reality, effectively two-thirds of what a real-world tire can handle.

The effect of this is that it begins to punish cars that use lower-profile tires as part of their design, which doesn’t accurately reflect the direction that real-world manufacturers are going, for better or for worse.

Any thoughts on this issue would be appreciated!


#2

Is this all constant throughout the years too?

Also how about tire grades? As in the class/grades of tires.
Same profile tyres could have different load rating depending on their ‘quality’, no?

Even if not, how close to the rl would you consider accurate enough?


#3

Yeah, it looks like it’s consistent year to year, which is pretty accurate to the real world - looking through the owner’s manual from a car now 20 years old, it gives the exact tore specification, right down to the load rating - which if you look the tire sizes up today, the load ratings remain the same. Also, changing between the different tire compounds makes no difference; this is pretty accurate in that an all-season tire of a particular size needs to deal with the same kind of loads as, say, a high-performance summer tire or even an R-compound tire. Quality makes no difference, and I’m not really sure it should in my mind - again, even the crappiest all-season tire will have broadly the same load rating as even the most expensive summer tire.

As for accuracy, I mean if real-world accuracy is possible then great, but if not, just closing the gap between tire profiles would be good enough.


#4

Thanks for looking into this, it is something I noticed too but have not had time to investigate and address yet.
This looks like there is a pretty simple solution. 5% extra load cap for high profile tires, 10% extra for low profile tires, lerp in between. That will make it accurate enough.
Cheers!