So I went to the dealership...

I went to the Jeep dealership last week to get my oil changed and have my fog lights enabled, DRL lights set and have them adjust for my tire size (255/75R17).

The technician that worked on my car managed to get the DRLs working (I had to tell him the procedure - thanks to others who have posted it elsewhere), but he couldn't find a menu giving me a choice for which of the lights would come on for DRL (I wanted the high beams). Luckily, the high beams are what came on by default. He was concerned about switching the car to Canadian and back (necessary to enable DRLs) and told me that I'm on my own if the change screws up the computer. I know enough Commander owners have done the same thing so I told him to proceed. Not surprisingly, everything's fine.

The one thing that he could not do is change the tire size to match my tires. He (and by now, the service manager who came out of his hole when he heard the tech warning me about the DRL change) told me that the Starscan only has tires that Chrysler sold with the XK and my size wasn't listed. He gave me a choice of a few different sizes, but I'm not a tire guy so I told him to pick whatever he thought was the biggest in the list. He picked 245/60R18 (saying it's an 18" wheel so it must be bigger) but it made absolutely no difference in the speedometer being off - it's still about 10% slow.

I guess I'm going to have to pick up a Superchips programmer; something I've been thinking of doing anyway to try to improve my mileage. I'll just live with using my GPS for a speedometer until I can save up the buckage.

I told the service manager that I didn't want Chrysler to try to hose me later because my mileage is 10% low. He said the only time he's seen Chrysler have a problem with mods is when you get into 4" or bigger (never heard of bigger than 4" on an XK) because they make too radical a change in the drive train geometry.

So now, at least my fogs are working and the DRLs come on. The DRLs are a little odd though -- when I hit the turnsignal, the light on that side of the XK goes out and stays out until the turn signal is canceled. Do all y'all with DRLs activated have the same behavior, or is there maybe an option in Starscan that turns that off? It's nothing I can't live with - it just makes the XK look like one headlight is burned out when I'm signaling a turn.

I asked them how much to change the fluid in the transfer case, & differential -- $250. I guess I'll be going through those DIY videos and doing it myself..

$50 for the oil change and tire rotation, $55 for the Starscan work. Could have been worse (they wanted $100 for the starscan changes last time I asked them).

Regarding the tire sizes, you have a 32" tire (diameter). Any 32 inch diameter tire on his options would get the speedo calibrated. The 245/60/18 is the same diameter as stock which is 29.5 inches.

Here's a tire calculator link.

http://www.discounttire.com/dtcs/infoTireMath.dos

I read on another forum about people having issues with the DRL pulsing with the turn signals. Mine do not. They come on and stay on...while in gear. That puzzled everyone at first. they switched to Canada and back but the lights wouldn't come on. So I went to leave and the DRL's come on
when I put it in gear.

Quote:

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Originally Posted by GPintheMitten

Regarding the tire sizes, you have a 32" tire (diameter). Any 32 inch diameter tire on his options would get the speedo calibrated. The 245/60/18 is the same diameter as stock which is 29.5 inches.

Here's a tire calculator link.

http://www.discounttire.com/dtcs/infoTireMath.dos

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One thing to consider. If you are running a 255/75R17 for example and the tire calculators say its 32 inches tall, you dont want to program 32 inches into your programer to correct the speedo. You need to actually measure the tire because its not going to be that tall when mounted on a vehicle. The best way to find out the diameter of a tire is to find the tires circumference and then divide that by pi (3.141593). This will give you the most accurate diameter since you are getting the rolling circumference of the tire. To do this, take a piece of chalk and draw a line down the side wall of the tire (perpindicular to the pavement) and continue that line onto the pavement. Then drive your vehicle forward so the line on the side wall does one complete rotation and is perpindicular to the pavement again. Draw another line on the concrete where the line on the sidewall touches the concrete and then measure the distance between the two lines on the concrete. This will give you the tires circumference. Then take that number and divide it by pi and youll get the actual rolling diameter. I have 265/70R17 on my XK which according to Goodyear are approx. 31.9 inches tall brand new. They are fairly worn now but when I measured them the other day using that method it came out to be 30.5 inces tall. I pluged that number into my superchips programmer and now my speedo is dead on to my GPS.

i think someone here should by a starscan and when a forum member needed something done the starscan would be Fed-exed to him, and then sent back after work completed. Sounds good , huh ?:cool:

That would be cool until it got sent to someone and that person never returned it.

Well, thats just a chance YOU will have to take. LOL

Has anyone with larger than stock tires managed to get the dealership to adjust for them, or is it (as it seems) only possible through Superchips?

I just wonder if anything other than MPH and MPG calculations are thrown off... Like traction control, ABS. The transmission is going to shift later since it thinks the XK is going ~10% slower than it really is.

I know there was a few members from jeepcommander.com that got their tire size adjusted by the dealer. They can only program certain sizes though like you mentioned in your first post.

Quote:

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Originally Posted by CrunchyWizard

So now, at least my fogs are working and the DRLs come on. The DRLs are a little odd though -- when I hit the turnsignal, the light on that side of the XK goes out and stays out until the turn signal is canceled. Do all y'all with DRLs activated have the same behavior, or is there maybe an option in Starscan that turns that off? It's nothing I can't live with - it just makes the XK look like one headlight is burned out when I'm signaling a turn.

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That's an interesting point. I remember reading about that before I had my DRLs done. Mine stay on all the time while signaling turns. Now, I don't think you have anything to worry about. If you pay attention to late model Audis with those neat LED DRLs, you will see that the DRL on the signaling side will also go out, so you are in good (and classy) company! :cool: