Can we have a discussion on the best method to measure tires?
Here are my viewpoints on the matter. Measuring a tire from ground to top of the tire has issues for a few reasons:
So that leaves us with two questions
In my opinion, the best answer to those questions is by measuring the circumference of an unweighted tire and then using d=C/π solve for the diameter, where d=diameter, C=circumference and π=3.14
In my case I took a string and wrapped it around the center tread of my spare 285/70R17 and marked where the string met.
I laid it out along a tape measure and measured 103"
Dropping it into the above formula I came up with d=103/3.14 which is 32.8".
According to my tire's spec sheets that's pretty hecking close. I think my specs call for a 32.7 and that difference could slight inaccuracies in my measuring device and/or be due to my wheel width vs manufacture wheel width.
I'm curious to see what others come up with using the above method (looking at you, BFGoodrich! )
Here are my viewpoints on the matter. Measuring a tire from ground to top of the tire has issues for a few reasons:
- It's impossible to account for the load from one vehicle to another as a comparison for what a tire will look like on one vehicle vs another. More weight in/on a vehicle will make the tire appear shorter.
- Air pressure will come into play here. Higher air pressure levels will show a taller tire.
- Tire load range may be a factor. E load tires may not be as affected by the above
So that leaves us with two questions
- What is the best way to measure a tire that eliminates those factors?
- What is the most accurate way to measure that ensures you're not affected by a parallax issue?
In my opinion, the best answer to those questions is by measuring the circumference of an unweighted tire and then using d=C/π solve for the diameter, where d=diameter, C=circumference and π=3.14
In my case I took a string and wrapped it around the center tread of my spare 285/70R17 and marked where the string met.
I laid it out along a tape measure and measured 103"
Dropping it into the above formula I came up with d=103/3.14 which is 32.8".
According to my tire's spec sheets that's pretty hecking close. I think my specs call for a 32.7 and that difference could slight inaccuracies in my measuring device and/or be due to my wheel width vs manufacture wheel width.
I'm curious to see what others come up with using the above method (looking at you, BFGoodrich! )