"Horace K. Sawyer" wrote:
>
>  Conversion to 15" rims and 205/75/15 Bridgestone 689 LT  on  91 auto Westy.
> These measure just under 27" diameter as best can tell.
>
> Speedometer appears to be reading lower than actual speed.
>
> Question is:  how much?

Horace,
Your speedo is reading low by about 5%, so when your speedo says you're
doing 100mph, you're actually going about 105mph! Better watch those
speedtraps.
Larry