Setting tires size on tazer mini (most tires are not true size)

[Paulocon]

Hello i have 37 inch km3 but heard they are actually about 36 inches

What is everyone setting for their tires at? True tire size or what it says on the actual tire.

Wondering how i should set my tire size when setting it with the tazer mini

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[Medsker]

When I set it on my tazer I just kept trying sizes and then checking it against my GPS until I got spot on. I also have 37" KM3's and my final setting was 36.52. That would be a good starting point for you. Good Luck

 

[Paulocon]

When I set it on my tazer I just kept trying sizes and then checking it against my GPS until I got spot on. I also have 37" KM3's and my final setting was 36.52. That would be a good starting point for you. Good Luck

Thank you for you response. What exactly are you checking to get spot on when you say checking it against your GPS? Location?

 

[Medsker]

I had a GPS program on my phone I used. After I was pretty sure it was right I also drove around town and hit all the speed limit signs that have radar speed on them. We have quite a few in my town. These were all reading the same as the GPS and Jeep.

 

[aldo98229]

They are 36.5 inches, actually —see here https://tiresize.com/tires/BFGoodrich/Mud-Terrain-TA-KM3-37X12.50R17.htm

BF Goodrich has a habit of rounding up to the next inch its tires in SAE sizes.

By contrast, General Tire, for instance, is true to size —https://tiresize.com/tires/General/Grabber-AT-X-37X12.50R17.htm

Best thing you can do is measure your tires mounted on the Jeep at the PSI you use.

 

[RedundanT]

All of the above. I used a level on top of the tire and tape measure to get an accurate measurement. Took several tries as the stupid Tazer with true tire size gave inaccurate speedo readings. So I input size and drive with the GPS app, then input size and drive some more, till it's spot on now.

 

[aldo98229]

All of the above. I used a level on top of the tire and tape measure to get an accurate measurement. Took several tries as the stupid Tazer with true tire size gave inaccurate speedo readings. So I input size and drive with the GPS app, then input size and drive some more, till it's spot on now.

The built-in speedometer calibration itself is off. My Sahara came from the factory with the speedometer reading 1.5 MPH faster than actual speed. It wasn’t until I swapped the OE 32.1-inch Bridgestone Duelers for a set of 33.2-inch KO2s that the speedo reading matched my actual speed.

When I went to recalibrate my speedometer now that I got 35-inch tires, I kept that difference in mind and selected a size 1-inch smaller than measured.

For instance, my 35-inch tires measure 34 inches mounted on the Jeep, so I selected 33 inches on the Tazer menu.

I still have to double check that I got it right...

 

[Goin2drt]

Measure the actual tire once mounted. Set the Tazer as close to that. Get out your Waze app and drive steady and see if your Speedo matches the speed on the app. If not adjust up or down until it does. Complete.

 

[Friday2322]

Thank you for you response. What exactly are you checking to get spot on when you say checking it against your GPS? Location?

Google map, Waze, etc. most of them display your speed via gps. It's a pretty simple process. Good luck

 

[oldcjguy]

Most accurate way is to measure the radius from the center of the wheel/axle to the ground with the wheel on the jeep. Then double it for diameter, that gives you an accurate "working" diameter. This accounts for compression of the tire from weight of the vehicle.

 

[stylett9]

As someone else mentioned, doing a true tire measurement with tape measure did not give accurate results for me either (others have claimed it gives spot on results). I used a cycling app on my phone called strava which tracks real time movement speed. I then bumped it up against a few radar signs in my town to verify.

Here's some details. I went from stock 285 to 315. the manufacture specs claim I went from a 32.8 to a 34.4. Jeep tuning from the factory had a designated size 32.6 and after tape measure, I was supposed to be 33.8. My speedometer was no where near accurate. After doing test runs with GPS on freeway using cruise control, I believe I've settled somewhere around 34.17, running about 36 psi cold.

 

[Spank]

What pressure are you guys running your KM3s? I'm running 37s as well, but keep them around 30 PSI and they measure barely above 35.5in.

 

[Medsker]

I run mine at 30 psi also. I think people are missing the point of this thread. It doesn't matter their actual size, it matters what you need to input into the tazer. When I set mine at 36.52 it doesn't mean that's how tall they are, it means when I input that size into the tazer the speedometer is correct. There is no way to measure tires to hundreds of an inch accurately anyway. At least not with a tape measure.

 

[Spank]

As someone else mentioned, doing a true tire measurement with tape measure did not give accurate results for me either (others have claimed it gives spot on results). I used a cycling app on my phone called strava which tracks real time movement speed. I then bumped it up against a few radar signs in my town to verify.

That's a Jeep for you. People can have the same vehicle, same specs, and make the same changes and get wildly different results. I've got mine set to 35.5" and it matches radar signs and fuel economy hand-calculations perfectly.

It doesn't matter their actual size, it matters what you need to input into the tazer.

It'll matter to your odometer. Every BFG off-road tire that's been made in the last couple decades has always been at least an inch shorter than its rated size. Jeep takes this into consideration from the factory as well. There's an inch and a half difference between the physical tire size and what's programmed into the computer on Rubicons (they did this on the JK, too). If you're telling your Jeep your tires are taller than what you're physically rotating, you're adding mileage that doesn't exist.

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