As I am always designing cars that I will never build I needed a simple way of guessing what the relative cornerng power of different types of layout may be and to help trade offs between width ( i.e tyre size), weight and power.
So " ready reckoner "
- total car weight in kg
- total width of tyres on one side on mm
- type of tyre - 1.0 = std road tyre 1.1 = road legal trackday , 1.2 = full slick
- track in mm - average of front and rear ( caters for three wheelers)
- likely C of G in mm.
Basic formula (a)
- weight in kg/ total tyre width - kg per outer tyre mm.
- first " improvement " - adjust value (a) by tyre factor to give value (b)
- second " improvement" - adjust (b) by rolling moment of ^2(average track/C of G height). to give value ( c )
so to take two extremes
1) basic ford focus (a) = 1334kg /(215+215mm = 430mm) = 3.10 kg per mm.
(b) = 3.10 * 1.0 tyre factor = 3.10
© = 3.10 * ^2(1554/ 500)= 5.5
2) bugatti veyron (a) = 1838kg/(265+305) = 3.22
(b) = 3.22*1.1 = 3.54
© = 3.54 * ^2(1690/400) = 7.22
I think the formula gives too much value to track/CG height as it suggests that tyre-for-tyre a Veyron won't out-corner a Focus but it will by 20% due to track width
Anyways its not meant to give an absolute cornering capacity but to allow different cars and weight/tyre size/ width ( ie drag) trade off's to be checked.
Please note the word " capacity" it assumes spring rates, camber curves etc will all be optimised for each car!
Edited by mariner, 22 June 2012 - 18:56.