LT Tire vs ST Tire
I assumed I wanted ST Tires for my camper and some people are telling me to go with LT Tires. Now I'm confused, and guess I shouldn't assume.
Forum Discussion
Francesca Knowles wrote:Huntindog wrote:
Here is a link to a very good explanation of the govt. testing requirements for each tire type. The actual govt. regs are available, but are difficult and time consuming to research as they keep referring to different sections of the law.
This person did all the work and put this together:
Plain English Testing standards for ST and LT Tires
That so-called "study" gives neither sources nor references of any kind for the information it purports to base its conclusions on. Well, except for nods to other posters here in the Forums. It reads more like a church bulletin than a scientific paper: preaching articles of Faith to The Converted.
Best advice given here came early on: Consult a local tire guy you trust, and buy accordingly."
How do you come to that conclusion when he posted this?
Barney
"The references for my evaluation may be found at the Federal Motor Carrier Safety Administration (FMCSA) webpage:
ST tire standard may be found at FMCSA Part 571, subsection 109.
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?chunkKey=090163348008f295
LT tire standard may be found at FMCSA Part 571, subsection 139.
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?chunkkey=090163348008f2a9
Part 571, subsection 139 references Part 571 subsection 119 which can be found at:
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?chunkKey=090163348008f29d
QUICK NOTES
Each standard for the ST and LT tires has definitions, significant constraints on labeling, etc. that I will not address. There are also tire conditioning (temperature), tire break in, etc. that are the same or similar for ST and LT that I will not address. The details are in the references.
The (3) endurance, and (4) high speed performance tests must not result in tire failure. Tire failure includes visual evidence of tread, sidewall, ply, cord, inner liner, or bead separation, chunking, broken cords, cracking, or open splices, not just a blowout.
TESTING - BEAD UNSEATING RESISTANCE
ST Tire: (reference paragraph S5.2.2)
The tire is mounted horizontally and a vertical load is applied to the tire’s outer sidewall at a rate of 50 mm (2 inches) per minute.
Increase the load until the bead unseats or a specified value is reached.
Repeat the test at least four places equally spaced around the tire circumference.
LT Tire:
Paragraph “S6.6 Tubeless tire bead unseating resistance” references the ST tire procedure noted above.
Conclusion:
The testing for bead unseating resistance is identical for a ST and LT tire.
TESTING - STRENGTH
ST Tire: (reference paragraph S5.3.2.1)
Force a 19 mm (3?4 inch) diameter cylindrical steel plunger with a hemispherical end perpendicularly into the tread rib as near to the centerline as possible, avoiding penetration into the tread groove, at the rate of 50 mm (2 inches) per minute.
Compute the breaking energy for each test point by means of a provided formula.
LT Tire: (reference paragraph S6.5.2)
Each tire shall comply with the requirements of S7.3 of 571.119, which is tires for vehicles weighing 10,000 lb or more. Per S7.3 of 571.119 for our example tire, the testing is the same as the ST tire procedure noted above."
