[Spridgets] calculating speed

[Dean Hedin]

I disagree.  A tire does grow in diameter as a function of the square of its rotational speed.
The steel belt limits this, but not as much as you think.  Basically the sidewalls move inward
and the center of the tread goes outward.

The growth is not much, but it is enough to impact the final drive/rpm calculation.

Tire Growth Factor = 0.000100 (Inches/(MPH*MPH)) 

so for 50 mph  0.0001(50*50) = 1/4 inch increase in diameter.

The above formula is probably generic, different tires probably behave a little different, 
but they will all grow with the square of the rpms.



----- Original Message ----- 
From: <Weslake1330 at aol.com>
Subject: Re: [Spridgets] calculating speed


> When I asked a leading tyre manufacturer this question they advised that  
> while there would be some tyre growth over the life of a tyre there would also  
> be a reduction in circumferance as the tread wore away.  Their general view  
> was that one cancelled out the effect of the other.
> 
> As far as circumference growth at speed goes for a typical road tyre - the  
> steel bands in the tyre's construction prevent this.
> 
> W e s l a k e 1330