rpm vs. mph

[Tom Wesenberg]

I just did Tom's math. I have 14.25 to center of hub cap with 19 inch tires. I get 2675 at 60 mph and 2006 at 45 mph with a 3.78 rear end
If I substitute a 4.11 rear end in the equation I get 2908 at 60 mph and 2181 at 45 mph. So either I have a 4.11 rear end or the tach is off. It is a Westach from Snyders.

Jack up one rear tire, put the ****** in high gear, then count the turns to hand crank the engine until the tire makes 2 revolutions. If you have 4.11 then you will have to crank the engine 4.11 turns. If you have 3.78 then you will have to crank the engine 3 and 3/4 turns.

Tom,
Did you cipher in the effects of eating too much apple Pi ?

Is it possible to eat too much apple pi?

 

[160B]

Do you know if the speedometer is accurate??

The odometer may be right on with mile markers but the speed cup may not be properly calibrated.

Take a gps with you and see if the speedometer is accurate.

 

[Tom Wesenberg]

Do you know if the speedometer is accurate??

The odometer may be right on with mile markers but the speed cup may not be properly calibrated.

Take a gps with you and see if the speedometer is accurate.

That's what I do. I check the mile markers over a 10 mile stretch, and also look at my GPS for speed. Both the odometer and speedometer are accurate within 2%.