Tire data for aero

[raptor93]

I am in charge of designing the Aero for my FSAE team in UAE.I am doing it for the first time and I have a doubt.Firstly according to me,the tire can perform best only at a particular peak normal load.After that the performance of the tire will go down.So ,I want to limit my downforce accordingly.Is the thinking correct?
Secondly I am referring to TTC data for my Hoosier R25B 20.5 x 7 x 13 tires in OptimumT to confirm the above theory.However my graph of lateral force vs normal load is linear.Even the graph of lateral friction coeff with normal load is a straight line.
So I am wondering if I am thinking along the wrong lines or I have done analysis of tire data wrong in Optimum K.

[ChrisWoods]

As the normal load on a tire increases, the lateral force the tire can generate will increase. However, the tire lateral force coefficient (Fy/Fz) will decrease with load, so that the curve of lateral force vs. normal force is non-linear. Since some tires are more sensitive to loading than others, and many tires are roughly linear for small changes in normal force, it's possible that your graph appears to be linear.

[Swiftus]

Add more load and see what happens.

[Claude Rouelle]

" Firstly according to me,the tire can perform best only at a particular peak normal load. After that the performance of the tire will go down."

How did you come with that deduction?

"So, I want to limit my downforce accordingly. Is the thinking correct?

I do not know any engineer would would like to milt the downforce. Limit the drag yes but no limit the downforce...

"Secondly I am referring to TTC data for my Hoosier R25B 20.5 x 7 x 13 tires in OptimumT to confirm the above theory. However my graph of lateral force vs normal load is linear. Even the graph of lateral friction coeff with normal load is a straight line"

Seriously doubting your analysis. Just make some basic sanity check by overlaying the real, raw data with your model and check if the model curves goes "though the middle of the points cloud". Re-read the OptimumTire help file.

[onemaniac]

Is it really linear? the load sensitivity index is a very small number. It may seem linear but when you fit a curve you'll find it otherwise.
Also... don't be trapped in a small domain for your design process. I hate seeing students trying to be fancy before understanding the basics.
Look at the big picture: your goal here is NOT about maxing out the coefficient of friction but to give the car most grip and traction possible. There should be no reason to limit your downforce (separate from drag).

[Claude Rouelle]

" Look at the big picture: your goal here is NOT about maxing out the coefficient of friction but to give the car most grip and traction possible."

Exactly!

Want a financial perceptive? Do you prefer to get the interest of 10,000 $ investment at 10 % return or the interest of a 100,000 $ investment at 5 % return?

Coefficient of friction is one thing. Maximizing pure lateral, pure longitudinal and combined grips is another.