The balsphemous Hethen once again writes,
>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
205 60 R13s have a rolling diameter of 22.6 inches.
This has been verified, but comes from Yokohama (A008RSII).
This tire will rotate 5.92 feet per axle rotation.
Since there are 5280 feet per mile, there will be 892.4 axle
rotations per mile.
At 1 mile per minute (60 MPH), the axle will spin at 892.4
RPM.
The drive shaft will spin at 3.888 times faster than the axle,
so multiply.
The shaft spins at 3470 RPM.
Since the driveshaft and the engine spin at identical speeds
in 4th (sans OD), this will be your net engine speed (at)60MPH.
If OD is selected, multiply 3470 * .80 = 2776 RPM.
So...
3.700 * 892 = 3300 RPM (at)60
3.888 * 892 = 4062 RPM (at)60
4.222 * 892 = 3766 RPM (at)60
4.555 * 892 = 4062 RPM (at)60
If your tach is in fact correct, you have got a 4.55 gearset in your car,
that or no 4th gear.
Dont feel bad though, when I bought my Alpine, it had one too (4.555=).
Sell it to some autocrossing alpine freak, or save it for me when
I break mine.
cheers
Jarrid "Too much math for one day" Gross
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 09:56:45 CDT