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Discussion Starter · #1 ·
Just put down payment on some new Rockstar Wheels and tires for a 2011 Wrangler Rubicon. The tires are 285/70 17. My question is how much will the speedometer be off? Is there any way to correct the speedo? This is our first Jeep and this is just the first of many mods to come.

Thanks

Lobo
 

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You can purchase an AEV Procal and it will allow you to adjust your tire size and correct your speedo and shift points if it's an auto.
 

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It should not be off enough for you to worry about. On my 15 willies, at 45 radar would show I was doing 45 or 46. That tells me less than 1 mph different at 45 mph. The shift points did not seem to change. The willies came stock with Rubicon tires. I change them out to Procomp 285/70/17. These new tires are 1/2 inch taller than the factory tires but were about an inch wider.
 

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The difference will be a percentage. If your new tire rolling circumference is 5% more than the old one then theoretically the speedometer will be off by 5%. Like the other poster said, a procal will correct for the new tires and some dealers will do it. If they charge for it, then I would just get a procal so you can do it yourself when you put 35's on next time and the 37's after that....
 

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I put 33 Goodyear DT on my son's 12 JK.

Before you spend money to recalibrate, compare the speedometer to a GPS. I found the difference at 55 mph to be less than 2 mph. Shift points were not affected, so I didn't bother to recalibrate.
 
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