Went to the dealer today and got my height adjusted on my 06' spedo went from 3mph fast to 7mph fast took it back and got adjusted to 285-70-17 and no change.

i have 305-55-20, 285-70-17 are closer to my size than the factory 265-70-17,

Any Ideas? does it take a while to adjust

 

I have nitto 295s on mine and had to put in the 285 that are found on PowerWagon as you cant dial it in direct...thought about the sizes like you are looking at but after running GPS and one of the cop speed viewers they put on side of roads....both had me within 1-2mph as best as I can tell so not worrying about it...

Should be automatic...one thing we found when doing mine is that the gear ratio and stuff were all wrong in my truck....they had it down for something else besides 3.73; tires were wrong...everything was f'ed up. Reloaded it correctly and things seem fine though not perfect.

When I decide to put in the Smarty or Superchip then I can dial her in exactly to tire circumference to get rev per mile....

yours is likely 4-5 mph off with that size tire....but then again working the ratio and all you might be close.

 

i explained it wrong

before i took it to the dealer when spedo showed 70 i was going 73, and i ask them to adjust size, they said they adjusted it to a 275-60-20 or something, i knew that wasnt close but i took it on the road and GPS said i was going 65 spedo said 75

took it back had it adjusted to 285-70-17( i have 305-55-20 - 33.25in) no perfect but closer than stock tires. Spedo is still 7 to 10 mph off 76 on spedo is 70 on GPS

 

Maybe the 06's are programmed differant than the 04's?

On my truck all I did was get my tire size and rev's per mile. The dealer then plugged in the DRB and adjusted the pinion factor (I believe). It's an exact measurement. My speedo matches the GPS speed exactly.

 

the 06s only allow you to use tires in the Chrysler-Dodge inventory...which means that are OEM on one of their vehicles. Largest tire they have is 285 for Dodge Powerwagon. You can compare your tire circumference with that of other odd sizes with low profile and huge wheels diameter and get pretty close sometime. Do a google search for one of the calculators....measure you tire circumference....plug it into calculator and make sure it is accurate...

then just go through sizes until you find one pretty close and write it down. go back to dealer and have them go through the OEM list on ECM until you find one and you are done.

You cant manually enter it yourself...so either have to live with CLOSE ENOUGH or buy a Smarty or SUperChip programmer and do it yourself.

 

they let me pick the tire out of the computer, i watched the guy program it, the 285 is 32.7 in. in diameter, the 305-55-20 is 33.2 which is better than the stock 265 which is 31.7 in tall, what i cant figure out is why i went from showing 3mph slow to 7mph fast, i thought it may just need a couple of miles to adjust but thats not the case, they programmed it with 2 different sizes and it is still 7mph off, i think they must have programmed something else wrong or something, i feel that if they put it back to stock it is still going to be off. 3mph slow sounds pretty good right now.

I also got the new flash that day, and a rollover hose or something