Tire size reality

skyhighZJ

skyhighZJ

Gov retirement < needs to live
Joined
May 31, 2012
Location
Aberdeen, NC.
So as I’m getting to that point of tires for Spare Change I’m met with the dilemma of what size is real and what’s made up. I just can’t understand why if a company makes a XX” tall tire does it actually, real world, only measure YY” yet they charge you more for a “bigger” tire. Not to say anything bad but or single anyone out but, for example, the ones @Brownsxj has for sale are labeled a 36” but as measured they are only 33.5”. Given they are used and tread has been lost due to mileage but not 3 damn inches. So, why do tire company’s not label their tires accordingly?
 
I had some 38x12.50-16.5 Swamper SXs that measured 36". Then had some 39.5x15.50-16.5 TSLs that measured 39", which is much better. Certain ones just run short.

My current 295/70-17 Coopers only measure 32.5" and not 33.25" like math says they would.

No clue why, but they always get shorter once they're mounted and loaded.
 
In the case of the TSLs that @Brownsxj has, aren’t they aired down a bit?

BFG is notorious for being short. Bunch of guys I used to know ran 35” BFG and they were only like 33.5”
 
Measurements are based on a specific rim size (narrower rim makes the tire taller), a specific PSI (higher pressure makes tire taller), and the unmounted diameter (they're flat on the bottom when they're on a vehicle).

That being said, they're still all over the place. BFGs measure short, Interco is typically close to advertised size.
 
Just to add some tech, my 43SXs are 41.5" at 8psi mounted on the vehicle.
It's VERY easy to change the OD by varying the pressure. And I'm talking a couple of inches easily.
 
skyhighZJ said:
So as I’m getting to that point of tires for Spare Change I’m met with the dilemma of what size is real and what’s made up. I just can’t understand why if a company makes a XX” tall tire does it actually, real world, only measure YY” yet they charge you more for a “bigger” tire. Not to say anything bad but or single anyone out but, for example, the ones @Brownsxj has for sale are labeled a 36” but as measured they are only 33.5”. Given they are used and tread has been lost due to mileage but not 3 damn inches. So, why do tire company’s not label their tires accordingly?
Click to expand...

You should know about shrinkage, low tire pressure :D:beer:and bigger than advertised.
 
skyhighZJ said:
But that part of what I’m saying is, you also are paying for a 40” tire to get the 37”. It just doesn’t pass the sniff test.
Click to expand...
Discount tire does a pretty good job on their spec page of telling you the actual dimensions.

But part of the challenge is where to measure from. And as stated what rim width and what psi.

there was a time, before they got super popular that a 37 sticky Trep was as tall as a 40 tsl…that’s not the case anymore
 
Really, you just gotta check the real specs, and know what you're getting... Most things that are sold by dimension don't use true dimensions... Lumber, Televisions.

Discount tire was mentioned, also, Simple Tire usually has a true diameter in the specs on their site, and manufacturers usually have the diameter in the specs on their website.

As long as there isn't an industry standard for measuring, you aren't going to find a truly accurate measurement for comparisons.
 
zuke said:
As long as there isn't an industry standard for measuring, you aren't going to find a truly accurate measurement for comparisons.
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Agreed, though one would think "listing the dimensions" would be a reasonable standard :laughing:
 
I guess I didn’t think this would go the direction I intended. I know tires wear. I know that rim size and level of inflation matter. My point was to ask if anyone knew why if I stand a brand new XX” tire next to another brand of the same dimensions they wouldn’t be the same and the only one to even remotely say it was @zuke that there are no industry standards. To me, that’s BS. I want a 37x12.50x17, at nominal inflation on a recommended rim diameter it should damn well measure 37” tall not 34 or 35 or 36; 37, cause that’s what I paid for.
 
skyhighZJ said:
I guess I didn’t think this would go the direction I intended. I know tires wear. I know that rim size and level of inflation matter. My point was to ask if anyone knew why if I stand a brand new XX” tire next to another brand of the same dimensions they wouldn’t be the same and the only one to even remotely say it was @zuke that there are no industry standards. To me, that’s BS. I want a 37x12.50x17, at nominal inflation on a recommended rim diameter it should damn well measure 37” tall not 34 or 35 or 36; 37, cause that’s what I paid for.
Click to expand...
But the point is, what are you measuring?
Where?
A 32” belt doesn’t matter 32 inches.
A size 12 shoe isn’t 12 inches
A footling hot dog ain’t a foot long
A quarter pound cheeseburger doesn’t weigh a quarter pound when delivered

I’m suggesting you are applying a standard to a product that the manufacturer, the industry and the distributors don’t share
 
zuke said:
As long as there isn't an industry standard for measuring, you aren't going to find a truly accurate measurement for comparisons.
Click to expand...
Ah, yes, standards! everybody wants a standard....
so lets get an ANSI working group together, put in a year of painful time to set a standard, so that they (ANSI) can make more money by charging people for the code regs for the new rules we set so they know f they meet it or not!
Everybody wins!

oh wait :D
 
Ron said:
But the point is, what are you measuring?
Where?
A 32” belt doesn’t matter 32 inches.
A size 12 shoe isn’t 12 inches
A footling hot dog ain’t a foot long
A quarter pound cheeseburger doesn’t weigh a quarter pound when delivered

I’m suggesting you are applying a standard to a product that the manufacturer, the industry and the distributors don’t share
Click to expand...
a 2x4 doesn't measure 2"x4".
a 4 wheel drive vehicle is almost never really 4 wheels with driving power

And for the EE tech nerds - an analog-to-digital converter (ADC) rarely has an ENOB that is anywhere close to the stated bit rate once your measure the real CMRR SNR. That's one that drives me nuts. "I paid a shitpile of money for this 24 bit digitizer, where are those last 2 bits of data resolution!"
 
The good news though is that tire size math applied to my condoms has kept the peace in my marriage. Who cares if we call it different numbers.
 
just the way it is unfortunately . my 35 inch mud grapplers are 34s in reality. and technically less than that once you account when they sit on the pavement with weight on them or aired down.
 
You should get some new 36" Super Swamper TSL bias plys they actually run a little bigger than labeled. :rockon:wider and taller...

Brownsxj's tires and wheels looks like a really good deal but they have been worn down to the wear bars and then re-grooved and they are mounted on very wide wheels making the tire less tall. Looks like they have been reincarnated & are on their second or third life but still a killer deal for wheeling tires at the price he is asking!

:beer:
 
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