[Boots61]

After adding new 285's on my 1500 I used the Superchips to adjust the speedo, I set it at 32.75. Using the GPS today I see my speedo is reading 2-4mph under the actual speed. Should I adjust the tire size to 33 or down to 32.50??

Thanks!!

 

[helo-pilot]

Superchips specifically measured the tires from top to bottom while the vehicle is on the ground. Don't measure side to side or use one of the online calculators. Just get a tape measure out and measure from top to bottom. I know it's not truely realistic, but that is the way the programming in the tuner is set for.

 

[quick99]

32.50

 

[chipraider77]

I noticed that 65mph didnt feel the same when I mounted the nitto 308/60-r17's . The mfg said the tire was 31.4 and the tire clacs all said 31.225. I had it set in the middle and it didnt feel right so i measured them and came up with 30.something. I changed the speedo to match and now all seems right