Why aren't tires as tall as they claim to be?

Just so everyone is clear on how I measured...

I took 3 measurements

1. Tire only (no wheel) got roughly 32"

2. Tire mounted on wheel @ 35psi and got 32"

3. Tire mounted on truck @ 35psi and got 32"

 

You, and the guy who said "because they can get away with it"

Both correct IMO

 

And to make it even more confusing.....

A 275 is only a 275 on a specific rim... then 275 is the section width, which is the widest part of the tire, not the width of the tread itself. The tread may only be 255 at the contact patch.
A narrower rim will pull the sidewalls in and narrow the section width and contact patch.

 

If you are not seeing a difference between 2. and 3., something is wrong with your measurement technique. There should be visible sidewall flex when the weight of the truck is on the tire

 

^^^that

 

Unless he's measuring horizontally

 

With my dynapro a yes I saw some sidewall flex. But with these cooper st, they are stiff (10ply, E rated). There was a slight flex but not enough to take away from the height.

 

Actual tire sizes can vary quite a bit from one manufacturer to another, regardless of the width of the wheel it's mounted on. Hardly any are the size they should be although I did have a super swamper one time that was true to size. (For example 33's will be 32 "point something"). I think that is what the OP was getting at.

 

Seriously? Ok, I have no visual aids (pictures) to paste here, but the reason why is an approximation (like a said earlier height was in relation to width), is because the heigth measurement is taken from the mid cross section of the wall as a percentage, why? Because you would have to figure out not only the radius of a quarter circle for each corner of the inside wall, but also the diameter to come up with an accurate distance from rim to top. Considering the tire is inflated to nominal capacity and free of defects, like layer thickness. That is the best way I can explain it. If you don't understand this, I'm done explaining.

 

Pretty much, yes.

I was really looking for others who have measured as well. I wanted to see if they measured out to what the tire height says. But this discussion has been fun!

 

I did enjoy reading it.
Mickey Thompson was the worst for me. I had a 35x12.50 r15 one time that I measured to be a little over 33 inches. That was about 10 years ago. Not sure if they have changed at all.

 

None of your posts made sense, sorry...

 

Thank you

 

I actually had a tire shop owner tell me that Mickey Thompson was the only mud terrain that was true to its size. Well from the tires I've seen, they are not. I've measured 33" mickey MTZ's that were actually 31.5".

It is good to hear some tires are acurate when it comes to size. Just gotta find them.

 

Could it be their advertised tire heights are when the tire is moving at a defined speed so it includes tire growth?