View Full Version : Torque needed to spin tires - need help

13-04-2016, 09:59
Hi fellow sim-grinders!

I'm trying to find out what amount of engine torque is needed to spin the tires when accelerating in straight line.

So far I build very simplified equation counting with:
- Static weight distribution F:R
- Static aero downforce distribution F:R
- Roughly approximated curve of increasing downforce with speed
- Engine RPM at max torque
- Gearbox ratio - gear ratio x final gear ratio
- Tire grip - possibly falling with increasing speed (???)

I figured out quite low numbers of torque suspecting wrong tire grip input numbers:
- First thing is basic grip coefficient of racing tire on asphalt of a race track. So far I found 0,55 - 0,6 of ordinary tire on road which looks too low for racing conditions.
- Second is the falling grip with increasing speed - I found it in tire physics files of GTR2 and rFactor (nowhere else) as "SpeedEffects". It says at which speed (about 300 m/s) grip drops to half and how much (12 - 35 of what????) this affects grip with changing load. - I am quite lost here. Don't know how exactly use those numbers - at least the second one. Better description is here: http://z13.invisionfree.com/TougeLife/ar/t93.htm

So I want to ask what could be actual amount of basic grip and do I have to use "Speedeffect" - is it something from real life or it was made just for those two simulation games?

I'll be happy for any contributoin to this topic and pardon my bad English.

Thanks Kunca.