I've tried the tire size conversion, +/- a few times and still can't get the speedo very close. The truck came stock with 245x75x16's and now I have 285x75x16's. It has an NV4500 and 353 gears.

What did you set your at?

 

I would measure one of your tires and start there. I think a 285 is around a 31" tire. IIRC

 

Never though of that. I was using one of the tire guides off of the internet. It measures 31 1/4 now. I'll give that a try the next time I drive the truck.

Thanks,

 

My 285's are set for 31.75 inches and my 315's are set for 33.25. Both are BFG All Terrains

Both measurements work out almost exactly to speed via GPS.

Jeff

 

Thanks,
That gives me a good starting point.

 

I have mine set at 32.50" for my 295's so that seems right in line. I haven't measured via GPS, but by mile markers on the interstate.

Brad