Folks -- Like many, I've been reading, analyzing, and digesting this topic via this thread and across other forums. After getting thru the 90 plus pages on this thread, I thought I would chime-in and add to this thread (!). I (and probably most) get the impression that there is a very big problem with ST tires per se (ie, not due to under-over inflation/overloading, etc). I'm not saying/implying that those who have had their share of issues with ST tires weren't in complete compliance with proper "tire usage." All I'm saying is that -- wow -- the perception is that there seems to be a tremendous amount of ST tire failures after reading these threads (hence the debate of moving to LT tires).
I recently came across some interesting NHTSA data regarding ST tires and it does NOT corroborate the ST tire failure picture as conveyed across the various RV forums.
On March 13, 2013, the NHTSA published (via the Federal Register) proposed rules to amend Federal Motor Vehicle Safety Standard (FMVSS) No. 110 to make it clear that special trailer (ST) tires are permitted to be installed on new trailers with a gross vehicle weight rating (GVWR) of 4,536 kg (10,000 lbs.) or less. It also proposes to exclude these trailers from a vehicle testing requirement that a tire must be retained on its rim when subjected to a sudden loss of tire pressure when brought to a controlled stop from 97 km/h (60 mph). See http://www.gpo.gov/fdsys/pkg/FR-2013-03-13/html/2013-05761.htm
As part of its analysis, some interesting data surfaced.
First, over a 15-year period of consumer complaints, NHTSA found only nine (9) complaints related to trailer tires. I realize that not everyone is going to file a complaint with NHTSA, but I would expect way more than 9 complaints related to trailer tires over a 15 year period, especially after reading of the numerous ST tire failures on the RV forums (again, not saying folks have not had ST tire failures, but just pointing out that there appears to be a huge disconnect between that which has been experienced and that which has been reported). Doesn't this strike you as odd?
Second, you get a real-life look into what happens when there is a trailer accident with respect to proper tire selection. The agency cited an example of a trailer roll-over, where the police accident report indicated that the tires were underrated for the vehicle at the time of the crash (the trailer GVWR was 3,825 pounds and the two tires had a combined load carrying capacity of 3,250 pounds). However, there was insufficient information to confirm that the tires could not carry the load on the axle because there was no information on how much weight was loaded on the trailer's axle and whether the towing vehicle was carrying any of the trailer's weight.
In any event, below are some excerpts from the Federal Register pertaining to the above:
"The agency has also reviewed consumer complaints made to NHTSA's Office of Defects Investigations, based on submissions of Vehicle Owner Questionnaires (VOQs) to identify safety problems related to tires. A search of that database in June 2012 revealed 963 complaints containing both the words ``tire'' and ``trailer.'' A review of the narrative of each complaint revealed that 942 of the VOQs reported tire issues on the towing vehicle, 10 VOQs involved tire issues on the trailer, and 11 VOQs were not sufficiently specific to determine if the tire issue was on the towing or towed vehicle. (Nothing in the VOQ data indicated any increased safety risk associated with the use of ST tires or tires with rim diameter codes of 12 or less compared to any other type of tire.)
"To determine if a safety problem exists, the agency investigated its crash data. As discussed in the prior section, NHTSA's crash databases were not sufficiently detailed to identify relevant crashes.
"However, the agency has reviewed the 10 VOQs identified in the prior section related to tire issues on a trailer. One complaint involved a truck towing another truck. This case was not considered relevant because the towed vehicle was not a trailer. Nine cases reported tire failure (either blowout or tread separation) of one or more trailer tires. Four cases resulted in trailer rollover, but none reported rollover of the towing vehicle. Seven cases reported property damage to the trailer or the towing vehicle. In one case, another vehicle was struck by separated trailer tire tread. There were no reported injuries or fatalities in any of these nine cases, and it does not appear that any of these cases would have been addressed by the rim retention requirement.
"For example, one case involving trailer rollover reported that the right trailer tire rolled off the bead on a curved section of roadway. The owner of the unspecified towing vehicle stated that the trailer was rental equipment. The police accident report indicated that the tires were underrated for the vehicle at the time of the crash (the trailer GVWR was 3,825 pounds and the two tires had a combined load carrying capacity of 3,250 pounds). However, there was insufficient information to confirm that the tires could not carry the load on the axle because there was no information on how much weight was loaded on the trailer's axle and whether the towing vehicle was carrying any of the trailer's weight.
