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CWtheMan · 12-18-2018, 04:51 PM

The FMVSS have had the same fitment requirements for RV trailer tires since before 2001. Their minimum require than is the same as now. OE tires must provide a load capacity equal to the capacity of the vehicle GAWR they are fitted to. Of course that’s modified to coincide with another statement in the standard that directs the trailer manufacturer to insure the fitments are appropriate for each fitment.

There have been two conferences conducted about FMVSS standards since 2001. In the conference leading to the rules changes in 2007, a committee discussed the subject of load capacity reserves for RV trailer tire fitments. The popular figure was 12-15%. NHTSA turned it down but left the door open for further discussions. Again in 2010 when major revisions were adopted and made a part of the standards pertaining to RV cargo and how it was to be accounted for; the tire reserve subject was again benched. It’s still benched. However, IMO, NHTSA will soon act on it. In the past there was not enough designated tire sizes for RV manufacturers to build to a specific GAWR without having to use tires with little retailer support. With the ST tire manufacturers stepping in with new sizes and numerous new load capacity capabilities, I foresee NHTSA stepping in and adding a load capacity reserve for RV trailer tire fitments such as they now do for the automotive market. Will it be the 10% now supported by RVIA or something altogether different but with the same effect?

You know, brands are a marketing tool. In the eyes of the governing body a ST205/75R14 by any brand name has the same strength in load capacity and uses any tire manufacturer's load inflation chart for that designated size.

To say tire "A" is more "robust" than tire "B" requires further explanation as to why one might have that opinion. Does tire "A" have something tire "B" does not have? Maybe a Nylon overlay. Not all ST tires have them. Extra rubber molded into the tire sidewall to help prevent sidewall scuff damage. Not all ST tire have that feature. Maybe you have one of the newer designs that are all steel. Guess what, they are usually regrooveable and that's surely going to add much more weight to the already heavier steel design. Some of the LT steel tires are also retreadable. That surely must mean more dense materials were used.

Another good one is tire mileage. How does one measure "good mileage" from a ST tire? Did the owner continuously acquire those miles by constant usage or was it acquired over a 3-4 year period with numerous months of inactivity?

I've read literally thousands of tire threads. Some you couldn't get me to comment on with a crow bar.

Here are some questions that are difficult to answer by most of the tire inflation people. What is over inflation and where does it start? What is under inflation and where does it start?

12-18-2018, 04:51 PM	#80
CWtheMan Senior Member Join Date: Feb 2010 Location: Taylors, SC Posts: 3,031	The FMVSS have had the same fitment requirements for RV trailer tires since before 2001. Their minimum require than is the same as now. OE tires must provide a load capacity equal to the capacity of the vehicle GAWR they are fitted to. Of course that’s modified to coincide with another statement in the standard that directs the trailer manufacturer to insure the fitments are appropriate for each fitment. There have been two conferences conducted about FMVSS standards since 2001. In the conference leading to the rules changes in 2007, a committee discussed the subject of load capacity reserves for RV trailer tire fitments. The popular figure was 12-15%. NHTSA turned it down but left the door open for further discussions. Again in 2010 when major revisions were adopted and made a part of the standards pertaining to RV cargo and how it was to be accounted for; the tire reserve subject was again benched. It’s still benched. However, IMO, NHTSA will soon act on it. In the past there was not enough designated tire sizes for RV manufacturers to build to a specific GAWR without having to use tires with little retailer support. With the ST tire manufacturers stepping in with new sizes and numerous new load capacity capabilities, I foresee NHTSA stepping in and adding a load capacity reserve for RV trailer tire fitments such as they now do for the automotive market. Will it be the 10% now supported by RVIA or something altogether different but with the same effect? You know, brands are a marketing tool. In the eyes of the governing body a ST205/75R14 by any brand name has the same strength in load capacity and uses any tire manufacturer's load inflation chart for that designated size. To say tire "A" is more "robust" than tire "B" requires further explanation as to why one might have that opinion. Does tire "A" have something tire "B" does not have? Maybe a Nylon overlay. Not all ST tires have them. Extra rubber molded into the tire sidewall to help prevent sidewall scuff damage. Not all ST tire have that feature. Maybe you have one of the newer designs that are all steel. Guess what, they are usually regrooveable and that's surely going to add much more weight to the already heavier steel design. Some of the LT steel tires are also retreadable. That surely must mean more dense materials were used. Another good one is tire mileage. How does one measure "good mileage" from a ST tire? Did the owner continuously acquire those miles by constant usage or was it acquired over a 3-4 year period with numerous months of inactivity? I've read literally thousands of tire threads. Some you couldn't get me to comment on with a crow bar. Here are some questions that are difficult to answer by most of the tire inflation people. What is over inflation and where does it start? What is under inflation and where does it start?