Speedo correction for larger tires?

[US6x4]

I haven't read of anyone doing this yet, but has anyone changed speedo cable gears to compensate for larger diameter tires? I did this on my highboy and the math is just a simple cross multiply & divide.

For example a 11.00-20 going to 16.00-20:

#original teeth/42" = #new teeth/53"

So if the original tooth count was say 16 (just for the example) the new tooth count would be (16×53)÷42 = 20 teeth.

Are there different speedo gears available? Are they a Spicer or Allison only part or a generic size?

 

[tommys2patrick]

Check on one of the parts sellers like Eastern Surplus etc. you will need to know the specific vehicle and other details before you look into it.

 

[Tracer]

US6X4 check Big Mikes. He has some speedometer drives for larger tires.