Miata Mailing List: July 1998, Message #1651

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Well, I was talking about stock class. And I think the reasons you cite are
mostly in favor of the smaller wheels. I don't understand how a larger
diameter tire/wheel means a larger contact patch - can you explain this as I
can't visualize it?

Tire/wheel diameter affects gearing obviously, and on some courses a
taller/shorter tire may put you in just the wrong gear. In general, a
shorter tire is going to let you accelerate faster in an autox, however. 

For a fixed tire/wheel height,  more wheel and less sidewall would be
preferrable, i.e. running, for example, at 205/50 15 would be better than a
205/55 14 (assuming identical height). However, 205/55 15, would not be
preferrable to a 205/55 14 (different heights) - I drive both these sizes
and there is a huge acceleration penalty on the 205/55 15.

Looking at the current sizes of R1's that are available, a 225/50 14 is
better than anythign available in a 15" size. 


(sorry for the slow reply, just back from vacation)

Craig 



> ----------
> From: 	SGT2@chrysler.com[SMTP:SGT2@chrysler.com]
> Sent: 	Friday, June 26, 1998 1:17 AM
> To: 	Craig Boyle
> Cc: 	miata@realbig.com
> Subject: 	RE: Do I need an R model? Yes!
> As for the smaller diameter tires being a benefit,
> I had to think about that one for a while.  I've
> also had some discussions with the race boys
> around here, and your assertion is contrary to
> popular opinion. This is what we came up with:
> 
> Smaller dia. tire advantages:
> -Less weight
> -Less inertia
> -Lowers vehicle c.g.
> 
> Larger dia. tire advantages:
> -Larger contact patch
> -Ability for bigger brakes (not an
>     option for stock classes though)
> 
> The change in gear ratios was not
> a definite advantage for either one.
> Optimal gear ratios are different for
> each track.
> 
> If the weight penalty is not severe,
> the larger contact patch is preferred.
> 
> I'd like to hear more about your smaller
> tire theory.
> 
> Steve T.
> SGT2@chrysler.com
> '99 Silver Sport
> Win on Sunday. Go back to work on Monday :'(
> 
> 
>