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I just got back from the dealer where I bought my cc a few weeks ago and I wanted them to check some stuff for me. one thing was the speedometer setting. and he told me that they could NOT change the speedo programming to compensate for 30" tires...or any tires for that matter...they only have 2 steeing one for the stock wheels and one for 20' wheels....what does the wheel (rim) size have to do with speedo setting.,....I'm flaburgasted

Edited title-HJ

They may only be able to adjust for sizes that were available to them or as options.
A creative tech can use gearing a wheel/tire sizes to get you close. They do not have the options that we have with the HPPIII, I am afraid.
I know on the fullsize the 20" rims were available for the Railroad vehicles.
If you are just wanting to adjust from 29" to 30" tires, they may not be able to help you. They should be able to correct for 31's though , as they were available for the Z's.
Clock yours and see just how far off it is.

Get the HPPIII. I got mine calibrated for 35's/4.88's. The setting that worked for that was 32's/4.56's. Since the HPPIII can be set for a max of 33's and 4.56's, like Henry said, I still had to be creative with the combo, but it's right on the money.

To my amazement, when I switched to 30" BFG AT from some very worn stock tires, my speedo was right on according to two GPS' and a calibrated speedo on a Crown vic Police interceptor.

border man wrote:To my amazement, when I switched to 30" BFG AT from some very worn stock tires, my speedo was right on according to two GPS' and a calibrated speedo on a Crown vic Police interceptor.

The same thing happened with my 30/9.50 yokohomas. Drove me nuts adjusting with my HPPIII programer. When I put the tire size back to stock it, was right on the money!

How do you know it's right...how do you test it exactly??

d=r*t ( Distance=Rate x Time)

Mile markers at 60 mph will give you an idea or borrow a GPS.

Yea, I use my GPS.