04 chevy speed way off

[kc_sheets]

ok i have a 04 1500 5.3 with a 4" rancho and a 3" body lift on toyo open country MT 37x13.50R22 i have played with the tires size and still cannot get the speedometer to meet the gps i lowed the size from 343x55r22 and when i hit 70 its 77 on gps. once i hit 50 thats when the descrepency starts it starts slow and gets bigger. I lowered the size to 325/50r22 and now its way off i got 15 and its 20. I use 50psi for my tires is there any other setting i should change.

[SIERRA_BOI]

Look at this thread....


http://diablosport.com/index.php?name=P ... ic&t=20973

I had to keep playing with my tire size. After one or two tries, my speedometer is dead perfect now...

[m8silverado]

Boy am I glad to hear someone else is having the night mare I had. j/k Here's what I did and it worked great. Measure the circumference of your tire and divide it by pi (3.14). You will be surprised at what you find. It won't even be close to 37". I work for a tire store that sells the Toyo MT's and I know what you will find. Put that number in your Predator in inches instead of the actual tire sidewall reading. I still had to go 1/2" smalller than what I figured but my speedo is dead on with my GPS. Let me know if this works for you and glad to help if it does.