Actual tire size.

[99 sr5 highlander]

So I took some measurements of my tires today, and was quite disappointed to find that my 265/70/16 michelin ltx m/s tires actually measured at 29.25". Pretty crappy considering they are technically supposed to measure at 30.6". These measurements were taken with tires inflated to 44psi with no weight on them.

So I thought It would be interesting to have a thread with our actual tire measurements.

 

[fourwd1]

That's nothing new. Tire sizes are exaggerated just like MPG ratings on cars.
The only accurate ones I've seen are Interco tires.

 

[WXman]

How are you measuring them? The listed diameter of tires on manufacturers' websites is not exaggerated. It's just that they measure from top to bottom, including the bulge of the sidewalls, when mounted on a specific width wheel (which will also be listed for you). If you measure this way, you'll get exactly what the chart says you should be getting.

If you measure from the ground up to the top of the tire in a straight line, you're almost always going to get a lower number because you're not including the sidewalls like the manufacturer did.

I've only seen two tires in my life that didn't follow this rule. Treadwright tires are exactly the height that is listed on their website. And this Hercules Terra Trac AT2 that I just bought for a full size spare is also the same height as listed.

 

[99 sr5 highlander]

Oh, thanks for the great info. I was just measuring from the ground to the top of the tire.

 

[WXman]

In my opinion, tire makers should adopt that way of measuring diameter as the new standard. That's what matters to the end user...how tall is the tire when it's on my vehicle? You know? So I think that's how they should start doing it. There's already a measurement for section width of the tire...so why do you need to include sidewalls in the diameter measurement also? Makes no sense.

 

[03_4x4Runner]

That's nothing new. Tire sizes are exaggerated just like MPG ratings on cars.
The only accurate ones I've seen are Interco tires.

This is pretty much what I have found over the years also.

 

[JB.]

So I took some measurements of my tires today, and was quite disappointed to find that my 265/70/16 michelin ltx m/s tires actually measured at 29.25". Pretty crappy considering they are technically supposed to measure at 30.6". These measurements were taken with tires inflated to 44psi with no weight on them.

So I thought It would be interesting to have a thread with our actual tire measurements.

That's weird. When I measured my 265/70/17 BFGs a while back they came out right about where they were supposed to.

Slightly more than 30" on the vehicle at 33psi. Add about 1 inch for the compression of weight and another 2/3rds of an inch for tread wear (16/32 new vs 5or 6/32 in the pic). Total it up and it comes out, if anything, slightly taller than the 31.6 calculated diameter.

 

[JB.]

The listed diameter of tires on manufacturers' websites is not exaggerated. It's just that they measure from top to bottom, including the bulge of the sidewalls.

Are you saying that the diameter is measured as the stretched length of the curved line in the pic?

Never heard of this. Do you by chance have a link?

 

[nevada]

That's weird. When I measured my 265/70/17 BFGs a while back they came out right about where they were supposed to.

Slightly more than 30" on the vehicle at 33psi. Add about 1 inch for the compression of weight and another 2/3rds of an inch for tread wear (16/32 new vs 5or 6/32 in the pic). Total it up and it comes out, if anything, slightly taller than the 31.6 calculated diameter.

its been my experience that BFG's measure fairly true to size.

 

[WXman]

Are you saying that the diameter is measured as the stretched length of the curved line in the pic?

Never heard of this. Do you by chance have a link?

Yes, that's how it's done. I don't know of a specific link to point you to, but you can email any tire manufacturer you choose and they'll explain it to you. That's what we did over on the Wrangler forums and some of the tire makers sent us some info. about it.