Keystone RV Forums - View Single Post

CWtheMan · 01-06-2019, 01:59 PM

This is an official tire size designation, ST235/85R16. It may be manufactured with more than one load range, such as LRE or LRG. Each load range normally has a standardized maximum load capacity and all tires with the same size designation and load range will conform to a standardized load inflation chart.

For reasons unknown by us users, different tire manufacturers may differ in maximum load capacity for the same designated tire size with the same load range letter. This seems to be happening with the ST235/85R16 LRG tires in todays market place. Some of the brand name manufacturers are using 4080# @ 110 PSI as their tires maximum load capacity and other brand name manufacturers are using 4400# @ 110 PSI for their tires maximum load capacity.

The situation is compounded by another similar tire size designation; the ST235/80R16 LRG has a single maximum load capacity of 4080# @ 110 PSI.

All of the 4080# tires legally qualify in accordance with FMVSS as Original Equipment fitments for vehicle certified 8000# GAWR axles. However, when the RVIA 10% load capacity reserve recommendation is applied they will not meet the requirements of that RVIA recommendation.

Now, the reason for rehashing this obvious problem. In my last post I used my own words to describe how tires with the same size designation and load range letter could also disqualify the 4400# tire on those 8000# axles if not properly identified or better identified. So I went to the FMFSS and copied, verbatim, the words the FMVSS uses to describe the situation. It's complicated and a lot of owners are going to install the wrong tires without knowing they did so.

"Each tire shall conform to each of the following: Its load rating shall be that specified in a submission made by an individual manufacturer, pursuant to one of the publications described for its size designation, type and each appropriate inflation pressure. If the maximum load rating for a particular tire size is shown in more than one of the publications described each tire of that size designation shall have a maximum load rating that is not less than the published maximum load rating, or if there are differing maximum load ratings for the same tire size designation, not less than the lowest published maximum load rating."

Will the trailer manufacturer inform owners which load capacity tire is used and if it's been derated in any way?

A similar situation has always been present with the designated size ST235/80R16 LRE tires. It became very apparent when a trailer manufacturer fitted certified GAWR 7000# axles with the two load capacities that qualified for that fitment, to later find themselves in a NHTSA recall situation for not properly identifying the tires load capacities. How many of you have 7000# axles derated to 6840? divide that by 2.....They were manufactured with three different load capacities, 3420#, 3500# & 3520# all @ 80 PSI. Many of the unpopular brands had the 3520# rating and were replaced with a more popular brand with a 3420# rating. A counter productive action, given that most trailer manufacturers were not providing more than a few percentage points in load capacity reserves, if any at all with their OEM tires. I often got hammered when I saw a tire post about using replacement tires with a 3420# on Certified 7000# axles and said something about it. (Maxxis was the popular brand. Their tires in that size description and load capacity are still rated at 3420#).

01-06-2019, 01:59 PM	#42
CWtheMan Senior Member Join Date: Feb 2010 Location: Taylors, SC Posts: 3,031	Tire Size Designation and load capacity This is an official tire size designation, ST235/85R16. It may be manufactured with more than one load range, such as LRE or LRG. Each load range normally has a standardized maximum load capacity and all tires with the same size designation and load range will conform to a standardized load inflation chart. For reasons unknown by us users, different tire manufacturers may differ in maximum load capacity for the same designated tire size with the same load range letter. This seems to be happening with the ST235/85R16 LRG tires in todays market place. Some of the brand name manufacturers are using 4080# @ 110 PSI as their tires maximum load capacity and other brand name manufacturers are using 4400# @ 110 PSI for their tires maximum load capacity. The situation is compounded by another similar tire size designation; the ST235/80R16 LRG has a single maximum load capacity of 4080# @ 110 PSI. All of the 4080# tires legally qualify in accordance with FMVSS as Original Equipment fitments for vehicle certified 8000# GAWR axles. However, when the RVIA 10% load capacity reserve recommendation is applied they will not meet the requirements of that RVIA recommendation. Now, the reason for rehashing this obvious problem. In my last post I used my own words to describe how tires with the same size designation and load range letter could also disqualify the 4400# tire on those 8000# axles if not properly identified or better identified. So I went to the FMFSS and copied, verbatim, the words the FMVSS uses to describe the situation. It's complicated and a lot of owners are going to install the wrong tires without knowing they did so. "Each tire shall conform to each of the following: Its load rating shall be that specified in a submission made by an individual manufacturer, pursuant to one of the publications described for its size designation, type and each appropriate inflation pressure. If the maximum load rating for a particular tire size is shown in more than one of the publications described each tire of that size designation shall have a maximum load rating that is not less than the published maximum load rating, or if there are differing maximum load ratings for the same tire size designation, not less than the lowest published maximum load rating." Will the trailer manufacturer inform owners which load capacity tire is used and if it's been derated in any way? A similar situation has always been present with the designated size ST235/80R16 LRE tires. It became very apparent when a trailer manufacturer fitted certified GAWR 7000# axles with the two load capacities that qualified for that fitment, to later find themselves in a NHTSA recall situation for not properly identifying the tires load capacities. How many of you have 7000# axles derated to 6840? divide that by 2.....They were manufactured with three different load capacities, 3420#, 3500# & 3520# all @ 80 PSI. Many of the unpopular brands had the 3520# rating and were replaced with a more popular brand with a 3420# rating. A counter productive action, given that most trailer manufacturers were not providing more than a few percentage points in load capacity reserves, if any at all with their OEM tires. I often got hammered when I saw a tire post about using replacement tires with a 3420# on Certified 7000# axles and said something about it. (Maxxis was the popular brand. Their tires in that size description and load capacity are still rated at 3420#).