The 32.5" BFG M/T KM's & Truxxx Fit Great!!!

[spun07RTX]

Originally Posted by Chris03HD

I know with my Harley truck, I can use the hand held programer to change the tire size, and it makes the nec. changes in the PCM.

hypertech power programmer

..I had one in my last truck, 96' 4" lifted tahoe, man that was a cool toy! not only could you adjust the speedo for large tires, you could also change the trans. shift points, and even advance the engine timing for added power(that requires premium fuel tho)

[VoicesInMyHead]

LOL This all reminds me of the Verizon Math problem! No offense to anyone, it just reminded me of it and the Verizon thing was hilarious! You have to take the time to listen to the recording. Unreal.

[geotech]

Originally Posted by roguemoog

No, your speedometer is showing a slower speed than you really are doing, so you're going FASTER than it's showing! Think about it!

Correct!

The factory tires are rated at 700 revs per mile (rpmi). That (in theory) is what the ode and speedo are keyed to. BFG's 32.5" dia are spec'ed at 640 revs per mile. That's a 8.6% decrease in actual revs per mile, meaning when you've gone 640 rpmi, the truck thinks that you have gone 8.6% less than a mile or 4826 feet.

If your ode & speed meters were 100% correct to begin with (that's a big if), then when your speedo registers 60mph with 640 rpmi tires, your speed is actually 65.2mph. 70mph on the speedo is the new 76mph!

[Chris03HD]

Originally Posted by roguemoog

No, your speedometer is showing a slower speed than you really are doing, so you're going FASTER than it's showing! Think about it!

Duh! I corrected myself, thanks.

[Chris03HD]

Originally Posted by spun07RTX

hypertech power programmer

..I had one in my last truck, 96' 4" lifted tahoe, man that was a cool toy! not only could you adjust the speedo for large tires, you could also change the trans. shift points, and even advance the engine timing for added power(that requires premium fuel tho)

Its a cool little toy, but mines a Diablo Sport tuner. That and the SCT tuners are the main hand helds for the Harley/Lightning crowd.