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Discussion Starter #1
Ok, first, yes - I did a search on the forum. And on the internet via Google for that matter. And I can find very little information on what should be done after a tire size increase as it relates to the vehicles computer.

On previous vehicles (read: much older) all I have had to do is replace the speedometer gear. Or not... but no computer to worry about.

On the XK the onboard 'puter controls so much - speedo, MPG calc, TPMS (maybe?)... Shift points..

So I wanted to hear from some other folks here whether or not they unplugged the battery to reset the computer after a tire size increase. I went from 245/65/17 stock tire to a 265/65/17. Not much of a difference, but I still want some opinions, please.

Thanks in advance!
 

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Disconnecting the battery will not reset tire sizes. The dealer can reset certain tire sizes using the StarScan tool, otherwise you will need to buy a programmer.

Here are the tire sizes that can be reset by the dealer with the Starscan tool. Otherwise you will need a calibration tool from Hypertech (http://209.12.144.2/Products/Speedometer%20Calibrator) or AEV (http://www.aev-conversions.com/products/modules/).

235/65/17 Wrangler HP
235/65/17 Eagle LS
245/65/17 Wrangler SRA
245/65/17 Wrangler HP
245/65/17 Wrangler AT/R
255/45/20 ZR20 ASP
245/60/18 Wrangler HP AW
245/45/20 ZR20 BSW performance
LT 245/65/17 Wrangler HP
LT 245/65/17 OWL A/T
235/65/17 XL BSW all season
245/65/17 R17 Bsw all season
245/65/17 BSW A/T
235/65/17 SL Wrangler S4
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The dealer is useless for this...........

Do yourself a favor and buy a speedometer calibrator......

I purchased the Hypertech 52001, it does gears as well.
 

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Does anyone have any "hard facts" on the effects of larger tires on the computer? We need to know, especially when it comes to stability controls.
 

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Discussion Starter #5 (Edited)
IamJEEP, do you know if the Hypertech module you mentioned will work with my 2008 5.7L? Can't find any confirmation on the interwebs.

EDIT: Never mind. AutoAnything website has 2008 5.7L HEMI as supported by this programmer. Thanks!!! follow up question for you, though... does any of the programming result in better MPG?
 

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IamJEEP, do you know if the Hypertech module you mentioned will work with my 2008 5.7L? Can't find any confirmation on the interwebs.

EDIT: Never mind. AutoAnything website has 2008 5.7L HEMI as supported by this programmer. Thanks!!! follow up question for you, though... does any of the programming result in better MPG?
Not sure yet as I have not driven with the new settings, that much. According to my gps, before i the programmer ilthe speedo was slow by 3 or 4 mph. Now its fast by 1 mph, thats the closest i can get it.
 
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