Speedo Fix for Old Ranger?

Question

Put new gears and tires in/on my 92 Ranger. My stock speedo gear was: 17 teeth-green (C7SZ-A). I had 3.45 gears and 25.9" (215/70/14) tires and now it's 4.10 gears and 31" (31/10.5/15) tires. Without the tire change I did some calculating and I think I'll need the 20 teeth-orange (C8SZ-B) speedo gear. How would I factor the tire change in? Someone told me I should be okay with my stock speedo gear, that it wasn't off by much, but I'd like to be sure before I do long distance on-road driving.

Thanks.

Hawk · Accepted Answer

I think you are probably right on with the 20 tooth gear.

your new tires are about 16% more circumference and using my limited math skills the 20 is just about perfect.

might be safer just to go find a measured mile and calculate it out though.

L8R, Jeff

TransSurgeon · Answer

take it out on the interstate and do a mesasured ten miles, using the milemarkersget back here with how far your speedo said it was, and we'll figure it out

Steve Barker · Answer

Just time it through a measured mile and get your actual speed. Then change the gear accordingly.

1 tooth = 4 mph.

if it's fast , add teeth

if it's slow , subtract teeth.

You could math calculate it to death and it could still be wrong. Timing it and changing it accordingly is a 1 step hit it right the first time proposition.

Speedo Fix for Old Ranger?

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