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Re: [Spridgets] calculating speed

To: "Dean Hedin" <dlh2001@comcast.net>
Subject: Re: [Spridgets] calculating speed
From: "Jim Johnson" <bmwwxman@gmail.com>
Date: Sun, 19 Oct 2008 00:32:21 -0500
Thank you, Dean!  Precisely my point. Considering all the factors involved,
we may well be looking at a speed variance of as much as 1 mile per hour!!
Hardly trivial in a race situation where hundredths of a second are
involved.

Cheers!!
Jim

On Sat, Oct 18, 2008 at 10:30 PM, Dean Hedin <dlh2001@comcast.net> wrote:

> 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@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
>>
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-- 
Cheers!!
Jim
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