>
>I've been running 205 60 R13's of various brands for a decade and have never
>run faster than 15 mph per 1,000 rpm.(eg. 4000 rpm's = 60 mph, etc) with a
>3.89 diff. The tach has checked out OK.
>
>?????????
>
>Dick Sanders
>
Dick,
for 205 60 R13's
total diameter = 13 * 25.4 + 2*(0.60 * 205) = 580 mm
the total tyre diameter is ~ 580 mm
this gives tyre circumference ~ 1810 mm
which gives 890 revolutions per mile (for the tyre)
(1609000 millimetres in a mile divided by 1810mm)
60 miles per hour is 1 mile per minute
so the wheels turn 890 times per minute
with a 3.89 diff the engine spins 3.89 * 890 = 3450 times per minute
therefore with your tyres 60 mph comes at 3450 rpm
this is 17.4 mph per 1000 rpm
If your guages differ by very much from this then there is something not
working properly, which should be expected because you're in an Alpine, right?
BTW:
185 70 R13's
diameter = 13 * 25.4 + 2 * (0.70 * 185) = 590 mm
this gives 60 mph at 3380 rpm
or 17.75 mph per 1000 rpm.
Anthony
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