Speedo Gears?

Landon116 · Aug 28, 2014

Can someone explain to me that if I install a higher tooth speedometer drive gear will my speedometer essentially show that my speed is higher? Or is it vise versa? Ive searched around and I cant find much. Or maybe im lost? Im not trying to solve a problem on my car, just a little ticket issue.. lol

Thanks guys.

rbohm · Aug 28, 2014

a higher tooth speedo driven gear slows the speedo down iirc

jrichker · Aug 29, 2014

It's a ratio problem, just like I learned in 4th grade math. It became useful and important in the 6th grade when I started building go-carts in my back yard. I had to understand how fast I could go with a 2 HP lawn mower motor...

21 divided by 8 = 2.625:1
20 divided by 8 = 2.5:1
19 divided by 8 = 2.375:1
18 divided by 8 = 2.25:1
17 divided by 8 = 2.125:1

21 divided by 7 =3.00:1
20 divided by 7 = 2.85:1
19 divided by 7= 2.71:1
18 divided by 7= 2.57:1
17 divided by 7= 2:24:1

The higher the resulting end number, the greater reduction in the speed of the output.

See the attachment for help your speedo gear selection.

For those of us too busy to do the math, see LRS speedo gear calculator
http://www.latemodelrestoration.com/products/Mustang-Speedometer-Gear-Calculator

Landon116 · Aug 29, 2014

jrichker said:
It's a ratio problem, just like I learned in 4th grade math. It became useful and important in the 6th grade when I started building go-carts in my back yard. I had to understand how fast I could go with a 2 HP lawn mower motor...

21 divided by 8 = 2.625:1
20 divided by 8 = 2.5:1
19 divided by 8 = 2.375:1
18 divided by 8 = 2.25:1
17 divided by 8 = 2.125:1

21 divided by 7 =3.00:1
20 divided by 7 = 2.85:1
19 divided by 7= 2.71:1
18 divided by 7= 2.57:1
17 divided by 7= 2:24:1

The higher the resulting end number, the greater reduction in the speed of the output.

See the attachment for help your speedo gear selection.

For those of us too busy to do the math, see LRS speedo gear calculator
http://www.latemodelrestoration.com/products/Mustang-Speedometer-Gear-Calculator

Thanks Jrichker! I have a few drive gears on hand and I was just wondering if the higher number of teeth on the gear would result in a lower speedometer reading. Thanks for the link.

Speedo Gears?

Landon116

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Speedo Gears?

Landon116

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