Just curious to start a discussion on the accuracy and repeatability of the TTC tyre data. I've also started a thread on the TTC forums which has some of the data I've been comparing (http://sae.wsu.edu/ttc/viewtopic.php?f=19&t=130) but I'd also like to start a discussion here as I think more people will see it.
Remember that TTC data can only be posted in the TTC forum, not here.
The problem I'm facing right now is the massive difference in the data for the control tyre between round 4 and round 5 of testing. I've compared the Hoosier 20.5x7-13 @ 10PSI on a 6" rim and found that the shape of the curves was essentially the same but the lateral force produced for a given normal force was remarkably different. Round 5 testing produced far more lateral force. That wouldn't concern me if that was the case for all tyres and you just had to scale data to take into account wear to the sandpaper belt or whatever it was that caused the difference. However when I compare the data for the same tyre @10PSI on a 7" rim the peak lateral force is similar, however there is a big difference in the load sensitivity and the shape of the curve is different. It's to the point I'm wondering if I'm somehow using the wrong data sets as they look like entirely different tyres. (In the TTC thread I've posted an explanation of which data sets I've used and how in the hope people can tell me if I've done something very wrong.)
So my question is, has anyone else looked at this? Does anyone have any experience with manufacturing tolerance on tyres or how the FY-SA curves change depending on the aggressiveness of the surface?
I imagine that not only the maximum force but also the curve of the tyre will change depending on the surface you're running on as the tyre will deflect differently if it's on a surface that makes less force. Is the tyre data even useful at all or is it unreliable and not representative of real world conditions?