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Discussion Starter #1
Hey guys, I'm getting ready to order some new shoes for my XK which will be one size larger than original (245/70) and I'm debating if I should purchase a speedo calibrator for about $200+ or pay the dealer around $90 to program my computer one time for proper tire size? What are your thoughts?

Orignally I was planning on purchasing a speedo calibrator but then I started to think when will I ever use it again? I would only go one more size bigger once these new shoes wear out but by then (+ 60k miles) I will probably trade in my XK if I haven't done so already at that point. I know that with a speedo calibrator it states that when I take in the Jeep for repair to the dealer the computer has to be reset to factory settings but if I get it reprogrammed at a dealer will that not be an issue?

Thanks for your feedback.
 

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$90 seems pretty high bro down hear its only $50. That being said $200 for one time use seems a huge waste of money to me. For another $150 you can get the programmer and change a lot of stuff. If it was me I would start shopping around dealer to dealer and negotiating with them 90 just to make some menu changes on a computer not cool bro.
 

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I've never heard of the PCM's/ or Body Computers having that feature, the ability to change the speedometer ratio's or calibrating the speedo. It makes sense, it would be easy enough to do, just never heard of it before. You quoted a price, so it sounds like you checked it out and confirmed its a feature that is useable.

Talk with the dealer about future servicing and PCM updates and if you'll have to pay to have it reprogrammed again.
...I know that with a speedo calibrator it states that when I take in the Jeep for repair to the dealer the computer has to be reset to factory settings but if I get it reprogrammed at a dealer will that not be an issue?
This doesn't make sense to me, why would the Dealer do extra work of reseting you PCM everytime you have service when, if anything, it would be detrimental to the customer?

If you have your PCM re-flashed with new Software, I could see that reseting the PCM back to factory conditions. And, yes, they do release new versions of the PCM software to address minor problems, and often instruct the Dealers to do certain updates anytime the vehicle is brought into service. BUT, that is NOT a garuantee that everytime you bring the vehicle in for service they are re-flashing or reseting your PCM. It may be a case of just informing the service people before you drop it off, of course that might mean you have to choose between PCM updates or your Speedo calibration.

Find out if the Speedo Ratio is stored in Volatile or NON-Volatile Memory. If its in Volatile memory, anytime your battery goes dead or you disconnect your battery, it will dump the Speedo Settings. If its stored in NON-Volatile Memory, like the VIN# and Mileage, you don't lose those settings if power is interupted.

I would think if the dealer was re-flashing your PCM, they would throw in the speedo setting for free, it would only be a few extra seconds to punch in some extra numbers with the tool they already have hooked up and are using. BUT, there are cases of Dealer trying to charge people for the PCM updates Chrysler tells the Dealers to give the customer for free, so I suspect most dealer will be charging that $90, even though its only an extra 1 minute of work.
 

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Didn't know the dealer could do that... let me know how it works out.
 

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I had mine done for $89.50. MY MPG has been off since they removed, dismantled and reinstalled my transmission. However, there are only 2 sizes the dealer could program to: 235/65R17 or 245/65R17. At least, this is what was written on my invoice, and this is what the service advisor told me when I picked up the Jeep. I have one size over tires: 255/65R17 - he used 245/65R17, and my speedo is just about spot on with the GPS. These tires are about 1/2" wider and 1/2" bigger in diameter. When I put the tires on, speedo was off as well as MPG. The program tire size flash put it back to normal. What is the difference in size of the tires between what you have and what you want? Save your $. :eek:rangehat:
 

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I went fromn the stock tires to 245/75R17 and my speedo is right on with no dealer reprogram of my PCM. I would check your speedo with a couple of diffrent GPSs first them deside.
 

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donkey, you have the same setup as i do. what is your mpg? city highway, avg????
 

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Discussion Starter #8
$90 seems pretty high bro down hear its only $50. That being said $200 for one time use seems a huge waste of money to me. For another $150 you can get the programmer and change a lot of stuff. If it was me I would start shopping around dealer to dealer and negotiating with them 90 just to make some menu changes on a computer not cool bro.
I did some shopping around when I was looking for a price to enable my tow and fog light relays and the average was actually about $95 to reprogram the computer, at least in Chicago that was the going rate for programming. I agree, not cool at all just to push some buttons.

I've never heard of the PCM's/ or Body Computers having that feature, the ability to change the speedometer ratio's or calibrating the speedo. It makes sense, it would be easy enough to do, just never heard of it before. You quoted a price, so it sounds like you checked it out and confirmed its a feature that is useable.

This doesn't make sense to me, why would the Dealer do extra work of reseting you PCM everytime you have service when, if anything, it would be detrimental to the customer?
Some members on this forum have talked about the dealer being able to program the PCM for proper tire size.

When I mentioned returning the programming to factory settings everything you visit the dealer for repair is actually recommended by the speedo calibrator, so with the same programmer you have to reset to factory settings before you go into the dealer then once they do the needed repair you can change the tire size settings back to what you need; see here: http://www.hypertech.com/ProductManuals/speedocalibrator.pdf

I went fromn the stock tires to 245/75R17 and my speedo is right on with no dealer reprogram of my PCM. I would check your speedo with a couple of diffrent GPSs first them deside.
I like your idea! Maybe I'll wait until after they're installed to see what the difference is since I'm only going from 245/65 to 245/70. I drive about 90 miles a day during the week so I want all my readings to be dead on, not only that but I want to make sure my transmission shifts are adjusted for a different tire size.
 

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What you really need is a Superchips Flashpaq. https://www.superchips.com/#pn=products&psn=jeepflashpaq

Besides being able to reset your tire diameter to get your speedo back in line, there's a zillion other reasons to have one. I run in performance 87 mode. It livens up the 4.7L and changes nothing in MPG. Stock mode feels downright gutless anymore. The transmission has a different shift pattern too.

You can also read engine diags in English, as well as monitor engine params in real time. I use mine in a cell phone holder, and watch several interesting items such as ign. timing, fuel rate, etc. It's really interesting to see them change from stock too. The timing is radically different in performance mode compared to stock.
 

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Discussion Starter #10
What you really need is a Superchips Flashpaq. https://www.superchips.com/#pn=products&psn=jeepflashpaq

Besides being able to reset your tire diameter to get your speedo back in line, there's a zillion other reasons to have one. I run in performance 87 mode. It livens up the 4.7L and changes nothing in MPG. Stock mode feels downright gutless anymore. The transmission has a different shift pattern too.

You can also read engine diags in English, as well as monitor engine params in real time. I use mine in a cell phone holder, and watch several interesting items such as ign. timing, fuel rate, etc. It's really interesting to see them change from stock too. The timing is radically different in performance mode compared to stock.
THAT would be worth the investment but the problem is that they don't have one for the 3.7L yet.
 

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Note: This is older info that was posted in a thread on 7-13-07, so it may be different now. In fact, I'm sure it is since starting with the 2009 MY 18" wheels were available.

These are the tire sizes that the dealer can program on the Commander with the StarScan tool:

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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Discussion Starter #12
Good info jeep5253, so that rules out that option. It seems like the only options via StarScan tool are factory sized tires... makes sense.
 

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If you have the money for the programmer I would just do it. Especially considering the miles you put on your XK I'm sure you would get a ton of use out of it. I know I hate the stock trans program my self.
I can't though, it's not available for the 3.7, they're discriminating us... ok maybe not, but still it's not fair.
 

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^ or the flex fuel 4.7
 

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This is an option that you may have already ruled out as not valid, but just in case,, When I installed my Superlift kit I also installed an "AEV"module from American Expedition Vehicles. Its primary function is advertised to correct ESP errors as a result of the lift. It does (and it works!) correct for 30'-37' wheels also. 2005 -2010 WK's and XK's so they say.. I'm not sure the cost as it came with my lift. Just in case it might be an option here is the link. http://www.aev-conversions.com/products/modules/
 
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