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

I've measured my last 2 sets of tires. Before my lift I had Hankook dynapro ATM 265/70/16. This tire either on truck or off measured 29" which if I were to go by the actual size, they should be 30.7", that's atleast 1.5" shorter.

Currently I have Cooper Discover S/T, 255/85/16 which means they should be 33.06. After measuring them on and off my truck they came out to 32". The difference here is atleast 1".

I'm wanting an actuall 33" tire. Has anyone else ever had this experience? Is this just the way tires are made?

 

The rim width will increase or decrease the tire height, but not by that much.

 

All relative. Right, not really.

 

The height is in relation with the width. For example:
275/70/16 will be not only wider but also taller than 265/70/16 and viceversa.
265/75/16 will not only be taller, but a bit wider than 265/70/16. Do I make sense?

 

So do you not know an answer

 

What he's saying is that when he inputs those numbers into the online calculators, they report that the tire should be 33" but the actual tire is not.

 

Yeah I get how that works, I'm just wondering why tires aren't as tall as they claim to be. Even a 33x10.50x15 isnt actually 33" tall, it's closer to 32" tall.

 

I know that it is true that they don't necessarily measure as stated. I'd guess everyone that measures comes up low.

 

According to the Cooper site they should be 33.21 " on a 7" rim


http://dev.ca.coopertire.com/Tires/Light-Truck/DISCOVERER-S-T.aspx

 

Maybe there using the same ruler as Subway....

 

What wheel width are you running OP ?

 

^ this exactly. It's not an issue at all, I'm just curious as to why the sizes are off. Also raises a question if an ACTUAL 33" tire (255 not 285) would fit without having to trim. My current cooper st don't come close to rubbing

 

I'm running a stock wheel from 2001. I beleive its 8" wide

 

With all due respect, I don't think you get it. Because of what I explained in my previous post is that a 33 tire is not going to measure exactly 33 inches, cause some of it goes to the width. Comprende?

 

using this calculation..is air pressure a factor?

 

All due respect, you're no getting it...


He gets how the ratio works. He wants to know why a 33" tire isn't 33" tall
I've never measured OP but I'm going to now. Curious myself.

 

Stock wheels are 16x7

 

That's why I said it's all relative. If they actually measured out they wouldn't fit.

 

He said that he measured them unmounted.

I can understand air pressure being a factor if the tires are on the truck and he's measuring from the ground to the top of the tire, but he's measured mounted and dismounted.

 

I'm not sure what you mean by "some of it goes to the width"?

255= width
85= aspect ratio (85% of width= sidewall height)
16= rim size

So I'm trying to understand what your saying, but I understand the width and the aspect ratio determine the sidewall height