Quote:
Originally Posted by nikitopo
Hi Matt 
In fact the total area of the contact patch is not changing. With a wider wheel/tire combo, you just change the shape and make it shorter and wider. Check a picture:
Wide tires provide mainly advantages in better heat management, because you have less tire deflection. |
The shorter wider contact patch also runs slightly cooler than the longer narrower one due to more favourable airflow. At very high heat loads, such as under fast track conditions, the low profile tire stays "in the window" for longer. A lot of heat is generated producing grip at the road surface in addition to the heat induced by the slip angle distortion. At the limits of traction you explore on the track the contact patch scrubs across the road, it doesn't just creep. The contact patch heats the tire while the rest of the tire is cooled by the airflow. The net difference is the cause of the temperature change. The shorter contact patch is cooled for slightly longer, proportionally, than the longer contact patch.
Lower profile tires reach peak grip sooner due to smaller slip angles but they also let go more abruptly when the slip angle limit is reached. The most difficult engineering problem facing the very first "ultra low profile tires", (meaning then 60 series tires!) was this abrupt breakaway characteristic pretty much engineered out now. Something similar occurred for similar reasons when radial tires first began replacing bias ply tires. The reduction of grip when the peak slip angle was reached was quite abrupt for a radial tire. We have all got used to that characteristic now since nobody fits bias ply tires any longer