Lex Garey wrote:
>Good day -
>Regarding speedometer errors with various tire sizes,
>Triumph_TR4@ridgecrest.ca.us wrote :
>
>>The formula for this is:
>>(Original Tire Diameter/Replacement Tire Diameter) x Indicated Speed
>
>>Speed at
>>Indicated Approximate
>>55 MPH. Tire Diameter (inches)
>
>>55 185/80/15 26.6
>>60 185/65/15 24.5
>>56 205/70/15 26.3
>>59 205/60/15 24.7
>>54 215/70/15 26.9
>>57 215/65/15 26.0
>
>
>Shouldn't the figure in parentheses in that formula be reversed?
>
>i.e. : (Replacement Tire Diameter/Original Tire Diameter) x Indicated Speed
>
>Larger diameter means larger circumference means more travel per
>revolution; so you're going faster, but the speedo doesn't know it.
Absolutely, they should be reversed. My Bad. If you will notice the
numbers in the chart are correct, I just typed the formula wrong. The
shortest tire in the chart reads the highest speed at a given RPM.
So Long,
Darrell Leach, KD6LRC DM-15, Ridgecrest, Ca
email: Triumph_TR4@ridgecrest.ca.us
http://www.ridgecrest.ca.us/~token/PAGE1.html
1962 TR-4 (CT5368LO) Everyday
1962 TR-4 (CT13108L)
1965 Spitfire Mk 2
1967 Spitfire Mk 3 In work, lots of 1500 stuff
Keeper of the TR-4 List, Version 2.0 availible.
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