Speedometer Calibration

[H2-T2]

I have dealer installed, 18 inch wheels and tires. I have noticed that the tires, (Nitto) are 32.99 in. diameter. The stock Hummer tires are 34.5. On a recent trip that is exactly 684 miles, my odometer registered 720 miles. My question is, how is the speedometer recalibrated? Is it a simple matter of the dealer getting into the computer and changing the settings? It is also throwing my speedometer off by about 4 miles at 70 miles per hour. Thanks for any advice. Gary.

[H2-T2]

I have dealer installed, 18 inch wheels and tires. I have noticed that the tires, (Nitto) are 32.99 in. diameter. The stock Hummer tires are 34.5. On a recent trip that is exactly 684 miles, my odometer registered 720 miles. My question is, how is the speedometer recalibrated? Is it a simple matter of the dealer getting into the computer and changing the settings? It is also throwing my speedometer off by about 4 miles at 70 miles per hour. Thanks for any advice. Gary.

[TBarrow]

I know there are places here in Houston that do that. Ask your custom wheel store or even a discount tire if you have them. I suspect you realize warranty runs out sooner also. When hypertech comes out with a computer upgrade that is an option for tire size adjustment. plus a little performance.

Black H2

[H2-T2]

Thanks for the reply. After discussing the problem with my dealer, I was contacted by MC-2, the company that makes the T2-Hummer wheel package. They informed me that NITTO now makes a tire that is the exact diameter as the stock tires (for 18 inch wheels). They have agreed to replace my smaller diameter NITTO'S with the new size. Problem solved. It is nice to deal with good people.
Gary (H2-T2)

[DVJ]

H2-T2, what are the specs on the Nitto 32.99" tires?

dvj

[H2-T2]

DVJ: The Nitto's with the 32.99 in. diameter are LT325/60R18. They are the ones that throw my speedometer off by about 4 mph at 70 mph. (speedo shows 74 mph, I am actually going 70)...Hope this helps.. Gary. H2-T2

[DVJ]

Thanks H2-T2. The lower profile tire will allow me to get the H2 into my garage w/o having to remove the roof racks. There must be some way to recalibrate the speedo for the different tire diameter.

dvj

[ELR]

H2-T2
What is the size of the new Nitto tire?(Like LT---/--R18) Is it still in the Terra Grappler series? I would like to also go with an 18" tire, but I have not found a tire for use mainly on the road that is 34.5" diam. and with approx. 601 revs. per mile.

[H2-T2]

ELR...From what I was told by the t2hummer people, it is the same NITTO tire that I have now, only it will be the same diameter as the factory Hummer tires, 34.5. These tires will supposedly hit our shores in early Jan. I took a long trip on the 32.99s, and I must say that the ride was exceptional. Also no road noise. The smaller tires also have the benifit of fitting into smaller garage openings. When I get more info, I will pass it along..Hope this helps.. gary