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Just got my new tires (Wrangler Duratrac's 285/75-16's) put on my 2015 JKUR. I'll post pics in a different thread. The listed diameter for these is 33.1", and the Tire Rack lists the stock BFG K/M's at 32.1". So not a big change, and I know the actually diameter (as they sit on the rig) could possibly be closer. I drove on the freeway and the speedo exactly matches the GPS speed readout on the 430N. I ordered, received, but did not open a ProCal.

The question is if the speedo seems to be spot on should I go ahead and make the likely very minor adjustment, or should I return the ProCal and get a chunk of my money back? Asked another way, is it worth about $130 to do the very mild calibration? I know the ProCal could come in useful while winching (and it does other things that I think I will never use) so keeping it isn't wasted money, but I'm trying to figure out what I am missing.
 

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How much road noise difference did you notice on the highway between these two tires? I am debating this same change and wondered about speedo also.
 

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Just got my new tires (Wrangler Duratrac's 285/75-16's) put on my 2015 JKUR. I'll post pics in a different thread. The listed diameter for these is 33.1", and the Tire Rack lists the stock BFG K/M's at 32.1". So not a big change, and I know the actually diameter (as they sit on the rig) could possibly be closer. I drove on the freeway and the speedo exactly matches the GPS speed readout on the 430N. I ordered, received, but did not open a ProCal.

The question is if the speedo seems to be spot on should I go ahead and make the likely very minor adjustment, or should I return the ProCal and get a chunk of my money back? Asked another way, is it worth about $130 to do the very mild calibration? I know the ProCal could come in useful while winching (and it does other things that I think I will never use) so keeping it isn't wasted money, but I'm trying to figure out what I am missing.
At this moment in time I'd say no your fine return it but, is this really it and down the road when you might really need it, are they going to be readily available or on backorder like they seem to be sometimes?
It's your $130. Not a lot of money for a piece of gear in the grand scheme.
 

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I went up in tire size, too, and my speedo, GPS, and calibrated Ultragauge all read within .5 MPH. So no ProCal for me (actually was looking at the SuperChips FlashCal). I asked my performance guy about it today, and upgrades, etc. He basically said that for a Jeep, any future [Flashcal] upgrades (like MPG tweaking, etc.) would be lost on a Jeep if I drive it over 56MPH on the road....IMHO..... CG
 

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Discussion Starter #5
How much road noise difference did you notice on the highway between these two tires? I am debating this same change and wondered about speedo also.
So, I only have a few drives today under my belt. So far I would say the noise is similar (on some surfaces a bit more, on some a bit less). Ride is actually a little harsher (could be because the Duratracs have an "E" load rating, and the stock BFG have a "C" load rating) but they were also aired up 6-8 pounds over what most on the forum suggest.

So that sealed the deal in terms of keeping the ProCal. I likely don't really need to adjust for the tire size (though I did) but the ability to decrease the TPMS warning pressure threshold may be huge (I am going to try them at 28 psi, which is under the stock 30 psi threshold).
 

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Also adjusting it for the proper tire size will also make sure your odometer is recording miles accurately. Why burn through miles on your warranty for nothing, right? :)
 

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More info which may or may not be 100% accurate......FWIW I have "HEARD" that the GPS and Speedometer are tied together....however that was on some of the "older" JKs. Another thing to keep in mind is the tires will "wear" so the difference may show up at a later time....and create issues. I bring this up as "you are probably okay" but just because it seems to be "working for you", it may not work for everyone......older JK different gears slightly "larger tire" their stock tire smaller.....a lot of variables. Just trying to point out that not all situations will be like yours.....(feel like I am starting to muddy the waters so will stop)

Bottom line I agree with keeping the PRO-Cal...in fact I will be ordering one here shortly once I get everything together on my '12 JK. I to am going Duratracs, but with the "P" rating on stock wheels, and small lift. I don't expect to see a lot of variation, but like yourself I feel it would be better not to have the annoying TPS light on all the time....GOOD LUCK!!
 

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When using the Pro-cal for tire size, do you program for height of the tire as it sits with the weight of the vehicle or the size on the sidewall?
 

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Discussion Starter #10
When using the Pro-cal for tire size, do you program for height of the tire as it sits with the weight of the vehicle or the size on the sidewall?
Directions say measure the front tire as it sits. My tires, which the tire rack lists at 33.1", actually measure very close to 32".
 

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Discussion Starter #11
Also adjusting it for the proper tire size will also make sure your odometer is recording miles accurately. Why burn through miles on your warranty for nothing, right? :)
The way I am throwing mods on this rig there isn't going to be much left for the warranty to cover. Bumper, winch, trail cams, and some under-armor coming soon. I've never heard my credit card cry before.

:bop:
 

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The way I am throwing mods on this rig there isn't going to be much left for the warranty to cover. Bumper, winch, trail cams, and some under-armor coming soon. I've never heard my credit card cry before.

:bop:
Chuckle. I'm probably close to that line, but I figure what the :censored: . Can't hurt to try to keep it as long as possible, and fight for a warranty fix if needed.

Mike has all the same mods listed in my sig on his 2013. He had the stupid oil housing leak that there is a whole thread about. Even with all those mods, they fixed it (and man, what a fix it turned out to be with their screw ups! :jawdrop:) with about 400 miles left to spare in his 3/36. :bop:
 

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Also adjusting it for the proper tire size will also make sure your odometer is recording miles accurately. Why burn through miles on your warranty for nothing, right? :)
Feel free to correct me if I'm wrong, but here goes. I just went from stock Sahara tires that were 255/70/18 to 275/70/18. On the road force balancer that they used at my local shop all five new tires measured at 33.45". One of the tire conversion calculators online lists my sizes as 32.1" and 629.5 revs/mile, and 33.2" and 608.6 revs/mile, respectively. The way I figure in actually cheating the warranty because the jeep tells the odometer that I'm going one mile every 629.5 revolutions when I'm actually going further than that. And that means I'm actually getting better mileage than the comp says, or at least not as far below lol.

I think I figured it up to where my speedometer is off about 3.5%. When my gauge says 70 I am actually doing about 72.5. Doesn't seem worth the procal to me unless I can void my warranty doing this did to odometer tampering...

Pics of tire difference with no load, mounted on stock 18s
 

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Feel free to correct me if I'm wrong, but here goes. I just went from stock Sahara tires that were 255/70/18 to 275/70/18. On the road force balancer that they used at my local shop all five new tires measured at 33.45". One of the tire conversion calculators online lists my sizes as 32.1" and 629.5 revs/mile, and 33.2" and 608.6 revs/mile, respectively. The way I figure in actually cheating the warranty because the jeep tells the odometer that I'm going one mile every 629.5 revolutions when I'm actually going further than that. And that means I'm actually getting better mileage than the comp says, or at least not as far below lol.

I think I figured it up to where my speedometer is off about 3.5%. When my gauge says 70 I am actually doing about 72.5. Doesn't seem worth the procal to me unless I can void my warranty doing this did to odometer tampering...

Pics of tire difference with no load, mounted on stock 18s
Sounds like you're coming out ahead on the deal then! Good job! :)

Moral of the story, make sure you do your calculations and see which way works better for you. :thumb:
 
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