Sunday, August 28, 2016

RV Trailer Tire Complexities

This topic is not as simple as it may appear. Can the trailer manufacture fit trailers with normal everyday Light Truck (LT) tires? Sure can. They can also use Passenger (P) or medium duty all position truck tires. However, Special Trailer (ST) tires were specifically designed for trailer axles. They have been around for more than 20. Presently they are evolving rapidly.

Because most states don’t have laws that require tire monitoring, vehicle owners rely on retailers to provide them with tires that are safe for the normal operation of their vehicles when it comes replacement time. The automotive industry in collaboration with the Tire & Rim Association (TRA) provide listings of suitable replacement tires for all normal every-day vehicles. The tire industry has standards for plus sizing tires for your every-day vehicles. None of that applies to RV trailer tire fitments.

RV trailer tire fitments are the same in one respect, the vehicle manufacturer is solely responsible for the selection and fitment of tires to all vehicles they manufacturer. For RV trailer owners that becomes a complex problem. Few will take the time to study and understand the intricacies of the system and how it is all meshed together.

The most important factor after the fact of tire fitment is certification. This is where the vehicle manufacturer swears to the National Highway Transportation Safety Administration(NHTSA) that the tire fitments depicted on the vehicle certification label are appropriate for that vehicle as long as the recommended inflation pressures are maintained as a minimum requirement. In doing so, the trailer manufacturer has taken the tire manufacturer off the hook - so to speak - of responsibility, as long as the tire has been properly manufactured and has no defects.

Therein lies the dilemma for trailer owners and tire retailers. There are no lists for suitable replacement tires for the RV trailer. Tire designs that differ from the Original Equipment (OE) tire design are not considered appropriate unless they are on the vehicle manufacturer’s optional equipment list for that trailer. The trailer’s owner’s manual is required to have a tire safety section. That section is going to tell the trailer owner to seek recommendations from the vehicle manufacturer for replacement tires. A follow-along statement may read “ use tires of the same size and load capacity as the OE tires“. Unbeknown to most vehicle owners is the fact that ST235/80R16E is a complete tire size. The ST locks in the appropriate tire design. The suffix “E” locks in the load range of the tire.

Tire manufacturers’ retailers are going to be very reluctant to replace the ST designed tire with any other tire design. Most trailer owners wanting to change designs will do so by buying the tire and having them installed by a tire installer unaware they are going to be used as replacements for another design.

Earlier I mentioned other designs. Some are unique and others are run-of-the-mill high production tires.

Passenger tires are currently being offered as options on some hi-end Airstream trailers. Evidentially Airstream feels they may be appropriate for their uniquely designed hi-end trailers.

A unique LT is often used as OEM by some trailer manufacturer’s for service on 7000# axles. Those LTs are specifically designed for trailer service.

Truck tires designed for low bed, high cube trailers are commonly found as OEM on trailers with 8000# axles. Some of them are European designs and only have a 62 MPH speed rating. If you want to travel at interstate highway speeds you will want to avid those 62 MPH tires.

Most of the major tire manufacturers have in their tire warranty packages a section labeled “things not covered”. In that section you will find a statement about misapplication. Almost always that is going to mean your warranty will be voided if you replace OEM ST tires with any other design.

Currently there is very little excuse for not using ST tires to replace OEM ST tires. Soon all ST tires coming in from off shore manufacturers will have speed ratings on their sidewalls. Those ratings will always be higher than 65 MPH and seem to be leveling off in the 75 - 81 MPH range. All of the smaller ST tires in sizes 12” - 15” have a wide range of load capacity selections. A lot of the 15” tires now have a LRE in their desired load capacities. The 16” tires range from 3000# of load capacity to 4080# of load capacity.

There is not much name brand loyalty among trailer owners so ST tire manufacturers are often changing names for some reason or another. Sometimes vehicle manufacturers use borderline load capacities that cause the OE tires to have a very short life span and give the brand a bad reputation. Not to worry, the name will be changed. Sometimes ST tires that are cheep are 100% cheep, their name will change.

I guess the bottom line is tire manufacturers are going to go along with the vehicle manufacturers and not get into a long legal battle with them which they will surely lose because NHTSA stands with the Vehicle Manufacturers.

Thursday, March 3, 2016

Tire Inflation pressures for your RV trailer

Government and tire industry standards agree. The correct inflation pressures for your RV trailer tires are determined by it’s manufacturer and depicted on the Vehicle’s certification label, in it’s owner’s manual and on tire placards. They are called, “Recommended Cold Inflation Pressures”.

Normally - over 95% of the time - recommended inflation pressures for RV trailer tires are going to be the same as the maximum amount found on the tire’s sidewall. That leaves zero room for adjustments. OOPS, there is a way for adjustments to be made. Go to a good set of vehicle scales and see what the weight is for each wheel position on your trailer. Then use those findings to balance your cargo load so no tire is overloaded. It may require unloading things to your truck or just not carry them.

Replacement tires must provide the same or more load capacity than the Original Equipment tires. Replacements with excess load capacity by inflation can be adjusted up to the maximum load capacity shown on their sidewalls. But, you should still weigh your trailer and balance it’s cargo load.

Don’t be duped by recommendations to air your tires to the load carried. That’s what truckers do and you can see the results on our highways all across the country. The FMCSA has no provision for recommended tire inflation pressures. The inflation pressures for our RV trailer tires (any design) were set in motion by FMVSS. Don’t let those that want to use trucker regulations confuse the RV trailer tire inflation subject. What is good tire inflation for tractor-trailer tires is not good for RV trailer tires.

Bottom line: At replacement time get tires with 12% - 15% excess load capacity above your GAWRs

Tuesday, December 20, 2011

Why do so many trailer tires (ST) fail?

There is no clear answer, only speculation. Anecdotal information drives speculations into name calling and negative design confidence.
As everyday tire users we are spoiled. We don't suffer tire failures with our everyday vehicles. When we do they can almost always be accounted for. Most of us will go for many years without a single tire failure. Then we get an RV trailer and POP goes the tires.

The tires on our everyday vehicles are - in most cases - specifically designed for the vehicle they are on. They are quality graded for all sorts of conditions with tread designs to match the grading. Their load capacity has been derived from the maximum loaded vehicle with a 6% reserve left over which will seldom, if ever, be used. They are constantly in use so the built-in chemical compounds stay in action and degrading is held at the bare minimum. Most of them will wear out long before they will ever get old enough to be effected by degradation or age or both.

On the other hand the RV trailer also has tires specifically designed for their position. And that's where almost all of the similarity ends. Seldom has a tire design been scrutinized as often and with such detail as the ST tire. Almost all of the American manufacturers have given up on the trailer tire or have sent it to their off shore plants in faraway places like China, Vietnam, Korea, Taiwan or Thailand etc.

Most users that have had a ST tire failure or numerous ones are not going to like or agree with many of my analogies on this subject. The overwhelming evidence will support my stance but there are no official statistical findings to support what I say. But, logic always has a strong influence on many outcomes in the absence of other evidence.

In the absence of numerous recalls for the ST tire one must assume the design is sound and cannot, by itself, have caused the many failures reported against it.

Once the design is ruled out of the failure scenario  the cause must lie elsewhere. So, is there a single cause or a combination of causes? I like multiple causes over the single one. Of course any highly abused single cause can also be the culprit.

Here are my accusations. We overload our trailers. We speed with our trailers. We take a somewhat lackadaisical attitude about our trailer's tire pressures. We store our trailers for long periods of time - six months or more - with no regard for the tire's condition or pressures. The trailer may not even be level which causes tires on the low side to become overloaded for their entire time in storage. We don't balance or rotate the trailer tires. Sometimes the spare is
exposed to the elements for so long it explodes.