<VV> Speedo Question

[Ken Pepke]

Speedometer / odometers are calculated by revolutions per mile.  They are not dependent on the wheel diameter, 13 vs 14 inch, but on the rolling circumference of the tire.  For the speed to change that much the tire would have to be 33% larger in circumference.   That tire would not even fit on the front of a LM Corvair.  Modern tires of the same circumference as a stock 6.50 13 barely clear the fender during turns due to their wider tread.  

In your case, something else is wrong and re-gearing the speedometer is not a viable repair because the speedometer sees the revolution of the LF tire; one turn of the tire equals one turn of speedometer input, no gearing is involved.  Perhaps you could have the speedometer head rebuilt and calibrated to the circumference of the tires [not the rim diameter] you intend to use.  

Ken P
Wyandotte, MI
Worry looks around; Sorry looks back, Faith looks up.

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> From: "Bill H." <gojoe283 at yahoo.com>
> Date: May 10, 2012 9:11:40 PM EDT
> To: virtualvairs at corvair.org
> Subject: <VV> Speedo Question
> 
>                                                                B"H
> Hi all.  My 66 Monza came with two things among others:  14 inch wheels and a broken speedo drive.  I replaced the left front bearing cap and of course the speedometer started working again...I think the 14" wheels make the speedo reading pessimistic; it says 30 mph and I'm really going 40.  Anyone know if it's possible to re-gear the speedometer for 14" wheels?  Has anyone done this successfully?
> Thanks guys...Bill Hershkowitz 66 Monza Sport Sedan 110 PG A/C