Convert ST tires to LT tires

Red wing wrote:
Hi everyone

How do you convert ST tires size to LT tires size? For example 235/80R/16 load range E to a light truck tire size.

The 235 number is the width in millimeters. There are 25.4mm per inch, so 235mm*(1in/25.4mm) = 9.25"

The 80 number is the aspect ratio (sidewall height/width) which represents 0.8 ratio. So 235mm*0.8 = 188mm.

Converting the 188mm height to inches 188mm*(1"/25.4mm) = 7.4".

Since the side wall height has a top and bottom, the overall sidewall height is 14.8".

A 16" wheel + 14.8" of sidewall height means the tire is 30.8" tall unloaded.

So, the LT could be a 31" x 9" x 16" tire, or rounded some other way...

waltbennett wrote:
Truck tires have more flexible side walls as they may be on steerable wheels, trailer tires have stiffer sidewalls as they won't be steering.

If comparing LT to ST...then no, this isn't really true.

ol Bombero-JC wrote:
If it's inadequate - go to a different size, ex: 245/75 (which will be the same diameter, but 1" wider).~

245/75's are about 1/4" wider than the 235/80's. However, it most likely is less. The measuring rim used for manufacture specs on the LT245/75 is often 7" while on the ST235/80's it is 6.5". Thus if you mount a 245/75 on a 6.5" rim you'll be less than the 1/4" spec difference.

Use the load capacity rating. I suggest you buy tires that cover the entire GVWR of the trailer. Check wheel pressure rating before you increase pressure much.

Red wing wrote:
Hi everyone

How do you convert ST tires size to LT tires size? For example 235/80R/16 load range E to a light truck tire size.

Google is your friend..:C

Enter: "tire size conversion" (etc) -
several sites avail to enter size of tire you have -vs- tire size you are considering.

Results are in inches.

Handy for your example, as there are few (if any) LT tires available in 235/80.

You will have to go to 235/85 - check the diameter of the new tire size for clearance (between tires) via the conversion site.

Remember an inch larger in diameter results in loss of 1/2 inch per side - one inch total between the tires.
(235/85 is an increase of 1" in diameter over 235/80)

If it's inadequate - go to a different size, ex: 245/75
(which will be the same diameter, but 1" wider).

Be sure to check the wheel pressure rating - usually stamped on the back side of the wheel.

~

B.O. Plenty wrote:
My old Tow Masters were like bicycle tires compared to the Michelin Ribs I now have. You could grab one of the Tow Masters and wrinkle it up with one hand. In addition the Michelins weigh about 20 pounds more.B.O.

I found the same thing when I replaced my no name China bomb ST tires. They were very light and the sidewalls felt thin and flimsy. However, I too had heard that ST's were stiffer walled but in practice I find that completely false.

The only 2 ST tires I've had good luck with and no blowouts have been Maxxis and Hercules. That latter is one of the few ST's made in USA. All others I've tried, Greenball, Tow Master, Carlisle, Master Track have all blown out with low mileage and all had very thin weak sidewalls.

Me Again wrote:
The 245 is LT245/75R16! Chris

I typed that before my morning coffee! Corrected!

mileshuff wrote:
There are online sources that will tell you your tire dimensions. For ST235/80R16's you have 2 LT choices unless you can/want to go to a much larger or smaller size or change rim sizes.

The LT245/80R16's are very close to the same height and about .25" or less wider. The LT235/85R16's are about 1" taller and about the same width.

I went with the LT245/80R16 Michelin XPS Rib. My existing tires are on 6.5" rims. The Ribs manufacture width lists them at .25" wider but thats using 7" rims. When mounted on my 6.5" rims the width is just barely wider than the ST's. A very close match.

ST tires generally have a higher load rating than LT's but its difficult to compare. ST tires show the absolute max rating not to exceed. The LT tires typically are underrated by 20% to allow a safety margin.

The 245 is LT245/75R16! Chris

waltbennett wrote:
The numbers and ratings are the same. Only change is the letters. Truck tires have more flexible side walls as they may be on steerable wheels, trailer tires have stiffer sidewalls as they won't be steering.

If you compare them side by side (I have) you will find you have that backwards. My old Tow Masters were like bicycle tires compared to the Michelin Ribs I now have. You could grab one of the Tow Masters and wrinkle it up with one hand. In addition the Michelins weigh about 20 pounds more...The weight ratings are less with an LT tire over an ST tire but don't let that stop you. I replaced a 235/80/16 load range E ST tire with a 235/85/16 load range E LT tire. Mine have been trouble free for thousands of miles.

B.O.

The numbers and ratings are the same. Only change is the letters. Truck tires have more flexible side walls as they may be on steerable wheels, trailer tires have stiffer sidewalls as they won't be steering.