FastEagle wrote:
Unfortunately the TRA does not publish that information - unless you purchase their publication - so the general public only sees what the tire manufacture does say.
Now that you have said that the TRA does have speed charts for all tires maybe you can answer this query.
The only Michelin branded tire currently being fitted to any RV trailer axles is a European designed 17.5” LRJ truck tire. It’s being fitted to 8000# axles. That particular tire has a 62 MPH speed restriction as posted in Michelin’s tire data book. I have emailed them numerous times - changing my wording on each occasion - to inquire about the speed restriction. They have never answered me. From the information I have been able to gather the TRA says that tires of that design with speed ratings below 65 MPH CANNOT have their load capacity and air pressure manipulated to gain any higher speeds beyond 62 MPH. Can you substantiate that?
FE
First, if we go back to the theory of tires - which applies to ALL tires regardless - there is a relationship between maximum load, inflation pressure, max speed, road surface, etc. Defining the type of service also defines some of these aspects - and that type of service is delineated by the letters in front of or behind the tire size.
So, yes, there would be a change in max load, if a tire is used in a different type of service. There are also some differences in inflation pressure - at least that is the theory.
The particular tire mentioned is actually sized this way: 215/75R17.5 Load Range J. I don't find that in my 2005 TRA Yearbook, so I am going to have to dig up a newer version to see if it is in there.
I'll get back to you on this.
But before I leave this post: One of the things that has to be understood when we start talking about tires is the SERVICE. This affects the tire's design - and I don't just mean the tread pattern or the rubber compounbd. I mean the load/inflation pressure relationship.
To try to give end users who tyoically don't understand how this affects things, the tires are given those letters in front of or behind the tire size to help delineate what the service condition is. It is also typical that the tire size itself defines the service - although it is embedded in the tire size and no one produces tires in that size that are designed for some other type of service. When we start sliding back and forth between types of tires (as defined by those letters) we run into all sorts of apparent contradictions - but they are only contradictions if we neglect to specify the service conditions.
