Correct Tire Size

[wubicon]

What’s the absolute fool proof method of setting the correct tire size for my 4xe rubicon? I have the tazer mini and I have it set to 34.5 for my 315/70/17 tires. The tires are set at about 33-34 psi cold. I might be slightly off by 1 mph. Can I know what you guys are running it at with your similar setup of tires/psi

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[conFUcius]

What’s the absolute fool proof method of setting the correct tire size for my 4xe rubicon? I have the tazer mini and I have it set to 34.5 for my 315/70/17 tires. The tires are set at about 33-34 psi cold. I might be slightly off by 1 mph. Can I know what you guys are running it at with your similar setup of tires/psi

The Tazer has a fixed correction built in for the tire size you enter vs. what is used when computing the speed.

https://www.jlwranglerforums.com/fo...pshifting-after-tazer-mini.67997/post-1443329

 

[Ratbert]

The Tazer has a fixed correction built in for the tire size you enter vs. what is used when computing the speed.

https://www.jlwranglerforums.com/fo...pshifting-after-tazer-mini.67997/post-1443329

That seems like an extremely questionable approach in assuming that his users are ignorant of tire size discrepancies as well as assuming that all discrepancies are similar. And then he documents it as being in inches.

 

[BDinTX]

I measured ground to center x2 which I think resulted in 33.6". Whatever it is it's close enough for me. Somebody else on here said they use a GPS to show speed and then adjusted the tire size until the speedo and GPS match. I thought that seemed like a pretty good approach.

 

[stumblinhorse]

What’s the absolute fool proof method of setting the correct tire size for my 4xe rubicon? I have the tazer mini and I have it set to 34.5 for my 315/70/17 tires. The tires are set at about 33-34 psi cold. I might be slightly off by 1 mph. Can I know what you guys are running it at with your similar setup of tires/psi

Absolutely fool proof method is to find a relatively straight road of at least 2 miles. Reset your trip distance and have a gps app or equivalent set to measure your distance Traveled. Adjust tire size until they exactly match for that 2 miles traveled. Then go to 3 miles etc. The trip distance should exactly match your gps traveled.

 

[Jtclayton612]

I used GPS speed to match speedometer speed. My 35” KM3s ended up needing the like 34.4” option in the tazer, which makes sense considering we know they’re a little smaller than similar tires.

 

[Dr. RGB]

Just for reference, the new Flashcal+ that works off your phone has an automatic tire size calculator that uses your phone's GPS (https://www.holley.com/products/tun...eld_tuners/flaschal_plus_wireless_calibrator/). Put it in tire calculation mode and drive around until it tells you that it is good to go. It then writes to the computer and done. My MPH is now dead accurate and no need to select tire sizes. You could literally change your tire sizes whenever the weather changes.

 

[Ratbert]

Just for reference, the new Flashcal+ that works off your phone has an automatic tire size calculator that uses your phone's GPS (https://www.holley.com/products/tun...eld_tuners/flaschal_plus_wireless_calibrator/). Put it in tire calculation mode and drive around until it tells you that it is good to go. It then writes to the computer and done. My MPH is now dead accurate and no need to select tire sizes. You could literally change your tire sizes whenever the weather changes.

That's pretty damn slick.

 

[Discount Tire]

Just for reference, the new Flashcal+ that works off your phone has an automatic tire size calculator that uses your phone's GPS (https://www.holley.com/products/tun...eld_tuners/flaschal_plus_wireless_calibrator/). Put it in tire calculation mode and drive around until it tells you that it is good to go. It then writes to the computer and done. My MPH is now dead accurate and no need to select tire sizes. You could literally change your tire sizes whenever the weather changes.

Wow, that's awesome! Appreciate the info.

 

[HDSlowride]

About to mount my new BFG K02 315/70 R17 on Method wheels. I will be correcting the tire size using a Tazer. What is a bit confusing to me are the specs on the tire, right off BFG website. They give 34.4" for the 315/70 diameter. The website also says 604 revolutions per mile. If you do the math.... [(5280*12)/604]/3.1416=33.4" The revs per mile calculate to 33.4"
So which number to use? Calculated diameter or published diameter? Or just put a level across the top of the mounted tire and measure down to the floor?

 

[Philly_]

About to mount my new BFG K02 315/70 R17 on Method wheels. I will be correcting the tire size using a Tazer. What is a bit confusing to me are the specs on the tire, right off BFG website. They give 34.4" for the 315/70 diameter. The website also says 604 revolutions per mile. If you do the math.... [(5280*12)/604]/3.1416=33.4" The revs per mile calculate to 33.4"
So which number to use? Calculated diameter or published diameter? Or just put a level across the top of the mounted tire and measure down to the floor?

Have the same tires and Method wheels (17x8.5) set at 33.86 and it’s just shy of the actual diameter. Next size up is too large.

Using a GPS, I am going 71mph when my speedometer says 70, and the next size up says I’m doing 68mph when the speedometer says 70. Figured I would rather be 1mph off than 2.

 

[conFUcius]

About to mount my new BFG K02 315/70 R17 on Method wheels. I will be correcting the tire size using a Tazer. What is a bit confusing to me are the specs on the tire, right off BFG website. They give 34.4" for the 315/70 diameter. The website also says 604 revolutions per mile. If you do the math.... [(5280*12)/604]/3.1416=33.4" The revs per mile calculate to 33.4"
So which number to use? Calculated diameter or published diameter? Or just put a level across the top of the mounted tire and measure down to the floor?

Published diameter since you are using the Tazer. The Tazer has a correction factor built in, so the calculated tire size is smaller than what it is entered.

 

[Bigdave18629]

Have the same tires and Method wheels (17x8.5) set at 33.86 and it’s just shy of the actual diameter. Next size up is too large.

Using a GPS, I am going 71mph when my speedometer says 70, and the next size up says I’m doing 68mph when the speedometer says 70. Figured I would rather be 1mph off than 2.

perfect timing to find your response, getting ready to put my Tazer on this weekend with the exact same tire. You definitely saved me some time.

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