View Single Post
Old 02-10-2013, 09:32 PM   #517
Hoon Goon
Scooby Specialist
 
Member#: 335538
Join Date: Oct 2012
Chapter/Region: South East
Location: Hell on Earth
Vehicle:
2008 WRX - Hatch
WRB

Default

Quote:
Originally Posted by amalgrover View Post
So if stopping a vehicle is negative acceleration, and width of tires don't matter when it comes to negatively accelerating, then why does a wider contact patch matter so much during positive acceleration?

I am not trying to be rude or argue...I am just curious why in drag racing, road racing, etc., wider and stickier is better than skinnier and stickier. I feel that if you were correct, then every race car out there would be buying 165 width slicks instead of tires twice that width because the extra width is only gaining them weight instead of grip. It just seems to me that you are missing a variable in your equation somewhere...
Quote:
Originally Posted by JRCrutc View Post
Tires are a somewhat special case in the frictional force world. Here is an interesting article that explains why a wider tire (and therefore surface area) is better for stopping:

http://www.physics.sc.edu/~rjones/ph...efriction.html

The basic premise is that the tire road surface is not an idealized coefficient situation. The tire has the ability to shear at the contact point with the road and therefore the wider the tire the more shear resistance is available.

There are also deformation issues based on road conditions. If the road was extremely flat and the tire shear issue was solved then surface area wouldn't affect the situation as much (or at all).
I can dig it. I learn something new every day (at least try to). I did not consider the shear forces working on the tire at the interface. My old Statics and Dynamics professors would righfully give me an F. Thanks for the replies fellas!

****NOTE FELLOW NASIOCers: A GUY JUST ADMITTED HE WAS WRONG*****

I am a hydraulics/hydrology guy, but I still love the cars and thinking about this stuff!
* Registered users of the site do not see these ads.
Hoon Goon is offline   Reply With Quote