Looking for some quick, easy help with stock Overtrail wheel-to-fender-measurements!

[Bluegill]

Hello,

I neglected to measure my stock Overtrail tires before I took it in for a slight lift and larger wheels & tires.

See the example photos below.

What I am asking for is a measurement of your stock Unites States version Overtrail tire height with the stock Toyo Open County AT3 tires in size 265/70/18. Measure from the ground straight up through the center of the wheel to the visible top of the tread. Please measure both front and rear at stock air pressure. A measurement when tires are cold would be ideal.

I know that Lexus advertises the Overtrail as having a 33" tire but the true calculations for 265/70/18 are 32.62" and the actual true tire diameter is probably a bit under 32". Also, on the truck under the load of the truck, the tire is compressed a bit so it's probably more like 31.5".

I still have my stock Overtrail wheels and tires but they are no longer mounted on the truck so I can't get a true measurement.

What I am trying to do is calculate how much my odometer is now off from stock with my 35" tires. Using the GPS on my iphone, I figured that my speedometer is off by about 5-7 mph above 70 mph (it reads low, I'm actually going 5-7 mph faster). The odometer will be off by a similar margin. Now that I have larger tires, I am actually traveling faster & farther with each tire revolution than my truck's instruments are telling me. I want to be able to correct my mileage for fuel economy reasons and I also want to eventually figure out how to re-calibrate the truck. I'll attach a photo of my new tire measurement which now reads about 33 & 5/8 or 33.625". So my 35" tires are really more like 33.5s!

Thank you for your help, I appreciate it!

 

[SethGX]

It doesn't matter how tall they are under load, what you are trying to calculate is the circumference difference, because one revolution of your tire travels exactly the distance forward equal to your tire circumference. It doesn't matter if your tires are slightly aired down or fully inflated, you will still travel the same distance. The original tires have a circumference of 102.5 inches, and your new tires, if they are 35", would be 110 inches around. The difference is you travel 7.5 inches further with every rotation. 7.5 inches is just over 7% of your original distance. So now, whatever your mileage shows you can multiple it by 1.07 to get a better indication of actual mileage. Same with speedometer, so when it reads 70 you are actually traveling about 75mph.

 

[Todgrubbs]

I pulled this screen shot of the tire compare web site. I have been using it to check out what diff tires would do on my GX. Tire Size Comparison

 

[Bluegill]

It doesn't matter how tall they are under load, what you are trying to calculate is the circumference difference, because one revolution of your tire travels exactly the distance forward equal to your tire circumference. It doesn't matter if your tires are slightly aired down or fully inflated, you will still travel the same distance. The original tires have a circumference of 102.5 inches, and your new tires, if they are 35", would be 110 inches around. The difference is you travel 7.5 inches further with every rotation. 7.5 inches is just over 7% of your original distance. So now, whatever your mileage shows you can multiple it by 1.07 to get a better indication of actual mileage. Same with speedometer, so when it reads 70 you are actually traveling about 75mph.

I never really thought of it that way....if the tire is aired down, or even just slightly bulged at the bottom (as all tires are at normal pressure just from the weight of the vehicle), the overall tire circumference and therefore the traveling distance are still the same.

So it comes down to the true diameter of the tires.

According to the manufacturer's specs, the Toyo Open Country AT3 in stock size 265/70/18 is 32.6" and in my 35" size it is 34.5". The difference from original to 35" is 1.9" which equals 5.83% more than original. Based on circumference of stock 102.416" vs the 35's 108.385", the percentage is again exactly 5.83%.

Thank you for helping me see this clearly!