Tire size measurement methods

Chris said:
I'd considered that, but the way the OP took the time to type it out in a thoughtful way, it didn't strike me as actually being a troll thread.
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Fair enough. I actually appreciate the housekeeping. Things can get derailed quickly around here.
 
Rubicon John said:
Fair enough. I actually appreciate the housekeeping. Things can get derailed quickly around here.
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And that is my only intention, housekeeping.

If people want to talk politics, they can go in the Politics sub-forum. If they want to talk Coronavirus Topics, they can even go in that sub-forum as well.

My goal isn't to censor anyone, it's to at least have some threads where so-and-so won't stumble upon it in a Google search and have to wade through page-after-page of trolling before finding actual, good information.

If that's "censoring" then call it what you will. I just have a pretty good mental list of trolls / pot stirrers :LOL:
 
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samobius said:
You're right; this is a sensitive topic for some reason which is why I was hoping to bring some serious discussion into it.
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There is nothing serious about the topic of measuring a tire. Tire dimensions are nominal numbers, not exact science. Bur accurate measurements are in the manufacturers spec for each tire they make.

And there is nothing sensitive about measurements either, the sensitive thing is the person posting.
 
Mr. Bills said:
@Chris

If you had bothered to read my first post in this thread that you apparently now admit you censored, you would have seen that i agreed with OP that measuring circumference and dividing by Pi is indeed effective for determining tire diameter.

Its your board and you can do what you want, but censoring content because it isn't "useful enough" for you or forcing a stop to banter between members who are not objecting to it is a slippery slope that can destroy a forum.
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I welcome the administrators doing their job and keeping a thread focused....

Kudos to you Chris.....

Now back to the topic.
 
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I apologize; I wasn't trying to drum anything up. I just honestly come across posts that state "this tire runs small" and so I'm just trying to introduce a consistent method for determining actual tire size for verification. Are they actually smaller than their published circumference, or do they simply compress more than expected at a given air pressure and load.
 
I haven't run enough tires to know, but are there certain tire companies that over report tire size and companies that under report?

I've heard Coopers for instance run large, while BFGs run small.
 
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samobius said:
I apologize; I wasn't trying to drum anything up. I just honestly come across posts that state "this tire runs small" and so I'm just trying to introduce a consistent method for determining actual tire size for verification. Are they actually smaller than their published circumference, or do they simply compress more than expected at a given air pressure and load.
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You're not doing anything wrong by asking the question. I think this thread just flared up since a lot of people are still riled up about the similar thread from yesterday.

I'll admit that I honestly didn't know how to measure a tire. When I got my 315/70R17 BFG KO2 tires I had all 5 mounted and filled to 35 psi (they wouldn't fill them to 26 psi for some reason). I measured the spare tire mounted to the tailgate and came up with 33.3". When I originally bought them on the Tire Rack website, I had seen 34.4" for overall diameter, so I was expecting that was what they would measure at.

Anyways, this was a year or so ago, and at the time I honestly didn't know. I thought that's how the tire was measured.
 
I think the most accurate way to answer this question is to agree, as a forum, on a common measurement method. For example, we all measure horizontally with our rig as it sits at 26 psi.

We then make a table with all the different tires and measurements in it. That way, we know the difference between them, which is more important than the actual “height”
 
Rubicon John said:
I think the most accurate way to answer this question is to agree, as a forum, on a common measurement method. For example, we all measure horizontally with our rig as it sits at 26 psi.

We then make a table with all the different tires and measurements in it. That way, we know the difference between them, which is more important than the actual “height”
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That’s what I would think as well. Because I am guessing that when you ask the average person what their tire measures, they are simply going to go outside and measure it on their vehicle.

In my mind I always measured the spare tire mounted to the tailgate. With no weight on it, I always figured that was the size of the tire.

Now obviously that’s wrong, but I’m just saying that the laymen likely wouldn’t know that, and there’s nothing wrong with that either.
 
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Rubicon John said:
I think the most accurate way to answer this question is to agree, as a forum, on a common measurement method. For example, we all measure horizontally with our rig as it sits at 26 psi.

We then make a table with all the different tires and measurements in it. That way, we know the difference between them, which is more important than the actual “height”
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The problem with this method is I have an LJ while whoever else has a TJ - so there's a different weight component. The spare seems like a better approach, and yes at 26psi. So generally, yeah I agree with the concept :)
 
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Jeep on level ground, tire inflated to your satisfaction, one end of a 3ft. level on the top of the tire, other end in your hand, adjust for 'levelness', measure from bottom of level to ground. It takes all of 20 seconds to do this. You'll notice that your brand new 32" tire is only 31" working diameter. No big deal . . . 10W-30 Synthetic for northern climes 😷🐱
 
Take two tires mounted to rims and aired up, place them side by side a couple of inches apart on a level hard surface, garage floor for example. Place a straight edge across the top of both tires and measure the distance from the bottom of the straight edge to the floor and that will provide a 100% accurate measurement.
 
Vinman said:
Take two tires mounted to rims and aired up, place them side by side a couple of inches apart on a level hard surface, garage floor for example. Place a straight edge across the top of both tires and measure the distance from the bottom of the straight edge to the floor and that will provide a 100% accurate measurement.
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Isn’t this basically the same as measuring them while mounted on the spare tire carrier? The only difference being that they aren’t on the ground, but I’m not sure how much of a difference that would make in terms of measurement.
 
Chris said:
Isn’t this basically the same as measuring them while mounted on the spare tire carrier? The only difference being that they aren’t on the ground, but I’m not sure how much of a difference that would make in terms of measurement.
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Measuring the spare has to give the most accurate measurement.
 
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