Martin_A._Secrest@NEB.VOA.GOV wrote:
>
> Ian --
>
> The proper ªcorrection factorª for low profile tires is ... to go FASTER.
>
> You have to do this because ... your wheels are smaller.
>
> Forgiving my flip-ness, it is a good question. I have no idea how one
> goes about computing the difference. To my thinking,
> however, if the tranny reads ªone complete revolution,ª and that
> revolution is made with a smaller-than-standard tire, you are going
> slower than your speedo says you are. I have the same problem, having
> just converted to a smaller (but wider) tire. My experience is that the
> difference is about 5 mph in the 50-60 mph range.
I converted my TR6 to 215/60x15 tires in the late 70's. The lower
profile created about a 10% high speedo reading. The easiest way I found
to compute the error was to time myself at an indicated 60 mph using
highway mile markers. Since 60 mph is 60 seconds per mile, you can
compute your actual speed based on how fast you covered the (allegedly)
measured mile. Hope this helps.
Irv
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