Upsized tire with no recalibration - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 5 Old 07-25-2014, 01:36 PM Thread Starter
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Upsized tire with no recalibration

Hi all. So I am buying a 2-dr Sport locally, and have a tire Q. The PO put the bright 17" rims on (Sahara ones it looks like), and then upsized the tires to 275-55s if I remember right from reading the tire a few hours ago... anyways, the tire warning light comes on the dash and PO did not recal the speedo.

Now, I'm probably going to trade back down to stock wheels and tires for now, but until such time as I can, is there anything inherently wrong with this setup? Anything I should do?

thanks
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post #2 of 5 Old 07-25-2014, 01:45 PM
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The speedometer and odometer are both reading incorrectly. The only way to change that is to reprogram the computer using a Procal or something similar. If this were an older vehicle, I'd probably walk because the mileage could be tens of thousands of miles higher than what the odometer shows...but it's probably not too bad since this is fairly new.

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post #3 of 5 Old 07-25-2014, 01:48 PM Thread Starter
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Quote:
Originally Posted by Godholio View Post
The speedometer and odometer are both reading incorrectly. The only way to change that is to reprogram the computer using a Procal or something similar. If this were an older vehicle, I'd probably walk because the mileage could be tens of thousands of miles higher than what the odometer shows...but it's probably not too bad since this is fairly new.
Oh yes, I know it would impact the odo as well. It looks like this was done quite recently - the tires are still very new; Still, I am going to trade them out for stock as soon as possible to counteract that, and any resizing I do in the future will include recalibration.

- EDIT: PO got back to me and says they were changed between 3 and 4k ago, so... let's figure it out!
16/225 stock is 2054mm around, about 783.5 rotations per mile.
17/275 is 2307mm around. that's 9.96" more per rotation.
If I assume 3500 miles that's 2.74mil rotations, *9.96 is 27.3mil more inches traveled = 2.27mil feet = 430.72 extra miles over the odometer reading. I can live with that at the moment. =0)

EDIT AGAIN: fixed the math for 275s instead of the erroneously-written 255.

Last edited by MoreDakka; 07-25-2014 at 02:45 PM.
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post #4 of 5 Old 07-25-2014, 02:36 PM
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LOL at the math, it hurts my head.

No problems, been running the flat tire symbol for six years and 285/75R17 for about 3 1/2 years. I didn't notice any adverse effects.

I finally did the superchips a few months ago and recalibrated the speedometer. It's a little peppier now and the speedo reads correctly.

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post #5 of 5 Old 07-30-2014, 08:03 PM Thread Starter
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Annnnnd dammit, I was right the first time! they ARE 255s not 275s, so only 300-some extra miles on the odo.
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