Things to know about trailer tires

[Tireman9]

I understand the concept that when a wheel is only marked with a max load then there is an assumption being made by someone about the tire size.
I would think the wheel supplier would not agree that any inflation is acceptable as long as the load is not exceeded so if pushed I think they would provide some answer.

[Tireman9]

Originally Posted by MilCop4523

I merely referred to what my underwriter reflected upon. There is no question here about what excuses the insurance business does or does not do to avoid liabilities.
Similarly one cannot have a vehicle re-certified for carrying extra weight in a trailer by adding a heavier suspension, air bags or extra leaf springs and changing P rated tires to LT tires.

"increasing pressure in the tire apparently by all literature does not increase load carrying ability of the wheel itself.

Your wheel may have a max load capacity number stamped on it. I would contact the wheel company concerning wheel load & inflation capacity which is separate from tire load, inflation and speed capacity"

I'm pretty sure i said tire but it should have perhaps read tire and wheel assembly.

"Special Trailer (ST) Tire Speed Ratings

Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.
However Goodyear Marathon and Power King Towmax STR tires featuring the ST size designation may be used at speeds between 66 and 75 mph (106 and 121 km/h) by increasing their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.

Do not exceed the wheel's maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).

The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.

Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity."

http://www.tirerack.com/tires/tirete...jsp?techid=219
one of several sites offering the same information as my agent passed along.

For me this means making the tire stiffer with air will not permit overloading of the max limit of the tire which apparenlty is limited to what the tire is mounted to for air pressure....

for instance i would think that if we had 110 psi max tires and my rims were limited to 80 - we would have to fill those tires carrying the 110 psi max to a max of 80 psi or risk the rim failing.

Would i be correct?

IMO the tech bulletin from Goodyear only applies to Goodyear Marathon ST type tires and not to any other brand or design of tire and certainly not to a wheel.

[Airdale]

There is another side to the coin.

Tire manufacturers are required to list rims that fit every tire size they make (individually). Rim manufacturers are not required to provide load or psi limits on their rims. So, anyone with rims provided with OE tires must assume that the rims are qualified for the OE tires and any other tire of the same size can be used. OOPS! The other tire even though the same physical size may have a higher load capacity requiring increased inflation pressures. What to do? The rim manufacturer is required to put part numbers and serial numbers on his rims. When in doubt, get those numbers and call the rim manufacturer.

Some times OEM providers of rims will yield to the wishes of the vehicle manufacturer and put load capacities and psi ratings on OEM rims to that manufacturer. Usually an entire line-up of a model of RV trailers can be fitted with the same size tires. Other times the line-up is so long that the larger end will require larger tires and rims. To help keep their order sorted correctly the rims will be marked to match the tires. That way all tire/rim combinations can be shipped in lots for an entire production line.

[Tireman9]

Clarification
Each size tire shown in industry standards such as Tire & Rim Association list the range of rim width the tire size is approved for. i.e. 5.5 - 7.0 might be the rim width for one size.
I am not sure that every wheel is capable of handling the load of every size tire made that might be put on a specific rim. They might be but I wouldn't just assume the wheel is OK.
The 16" GY LR G tire is a good example. I doubt that every 16x 6 rim is OK for 110 psi.
I do agree it is best to confirm wheel part number capability with the wheel company.

[spock123]

On a tire that is stamped 3750lb does that mean the camper can only carry 15,000lbs.


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[nomad297]

Originally Posted by spock123

On a tire that is stamped 3750lb does that mean the camper can only carry 15,000lbs.


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Keep in mind that a certain percentage of your total trailer/5th wheel weight will be carried by your tow vehicle. If using the tire weight capacity as the only factor of how much your trailer can weigh, you can weigh more than 15,000 pounds -- how much more depends on what percentage of your trailer weight is at the front.

Bruce

[Tireman9]

Originally Posted by nomad297

Keep in mind that a certain percentage of your total trailer/5th wheel weight will be carried by your tow vehicle. If using the tire weight capacity as the only factor of how much your trailer can weigh, you can weigh more than 15,000 pounds -- how much more depends on what percentage of your trailer weight is at the front.

Bruce

You should have a sticker / plate with the stated GVWR which is the max total weight. Tires do not carry an average of total/number of tires as axle loads are not 50/50 side to side or even 50/50 between axle.

A good rule of thumb is to run no more than 85% of the max load number based on actual scale readings of individual tire loading.

[Airdale]

Once you own a trailer the total weight of that trailer is your responsibility.

It’s manufacturer will determine - according to safety regulations and standards - what it’s maximum/minimum load capacities are. Once they do that they will put the most pertinent information on the trailer’s federal certification label. On trailers, that label is found on the LH forward external portion of the trailer. It will have the GVWR, all GAWR values, tire and rim sizes appropriate for each GAWR and the recommended inflation pressures for those tires so that they will equal or exceed the requirements of each GAWR.

Somewhere in the other information provided to the buyer there is a vehicle manufacturer’s established hitch weight. It can be in the form of a range or a specific number. If a range has been used the lower figure is added to total GAWR. The sum must equal or exceed the trailer’s GVWR. After the trailer has been sold all hitch weight figures are the responsibility of the owner.

What is often misunderstood is certification. In this context it’s something official. By affixing the certification label to your trailer it’s manufacturer has affirmed those standards have been met and are the maximum/minimum standards for that trailer.

Often times you will see posts where owners are wondering why a tire retailer wont replace ST tires with LT tires. It’s because they know the tire design has been set by the manufacturer and is on the certification label. It’s also why tire industry standards require replacement tires to have, at a minimum, the amount of load capacity - by inflation - of the OE tires.

[spock123]

I was going to buy a Cedar Creek 36CKTS, I have a 32RL now and I have Goodyear G614 on the camper now. What I was going to do was trade out the tires when I brought the bigger camper but I know I can't do that now. My tires are rated at 110lbs of pressure, is 3750lbs. That is 15,000lbs and that is great for my camper, GVWR, I think. My camper total weight of everything is 15,000lbs which will never happen. That's with all tanks full. The new camper is total weight 16,000lbs, so I will have to put Goodyear H rated tires on new camper and 17.5 tires. I think the new Cedar Creeks come with 17.5 ST tires made in China. I plan to stick with Goodyear tires that's made in America


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[Tireman9]

Slight clarification on the ST - LT tire change topic.
As a tire engineer, I see no reason for an owner to not be allowed to change type tire i.e. P to ST or LT or change ST to LT as long as the new tire at its inflation has equal or greater load capacity to the OE tire at its inflation and the max inflation capability as identified by the wheel manufacturer is not exceeded.

[Blackhat6mike]

Originally Posted by Tireman9

Slight clarification on the ST - LT tire change topic.
As a tire engineer, I see no reason for an owner to not be allowed to change type tire i.e. P to ST or LT or change ST to LT as long as the new tire at its inflation has equal or greater load capacity to the OE tire at its inflation and the max inflation capability as identified by the wheel manufacturer is not exceeded.

If there is no reason to not be allowed to use other typed tires, why rate them at all, unless they have different characteristics built in to address different needs? If this is true, couldn't you just run ST tires on your car of truck? Just curious?
Have you ever known of a wheel [rim] failing do to over inflation? I've yet to find anyone that has FIRSTHAND knowledge of such and not "I've heard of it happening". My humble tire guy [been in the tire business over 50 years with his family] said he never heard of it happening. My wheels aren't marked with psi rating either front or backside.

[Airdale]

Originally Posted by Tireman9

Slight clarification on the ST - LT tire change topic.
As a tire engineer, I see no reason for an owner to not be allowed to change type tire i.e. P to ST or LT or change ST to LT as long as the new tire at its inflation has equal or greater load capacity to the OE tire at its inflation and the max inflation capability as identified by the wheel manufacturer is not exceeded.

I also share that opinion. But, it’s an opinion not supported by tire industry standards. The vehicle certification process is binding for the vehicle builders.

Lets get hypothetical along that line. The trailer builder certifies that ST225/75R15D tires are appropriate as original equipment. Putting that information on the certification label sets a minimum standard for that trailer. Because the ST tire is a completely different design, LT or P tires used as replacements for the OE ST tires become a misapplication. To compound that problem is wording in the owners manual saying replacement tires should be the same type and size as the OE tires. (Anything to do with vehicle safety found in the owner’s manual is mandated to be there by the DOT).Tire industry standards written by every major tire manufacturer agree that replacement tires must have an equal or greater load capacity when compared to the OE tires. And compound the problem by saying to use tires like the ones on the certification label/tire placard. Another compounding problem is the size tire I used to start this off has no equal in load capacity with other designed tires. Another compounding factor is the vehicle owner’s manual. Its not going to recommend anything other than the OE sized tires as replacements, or vehicle manufacturer recommendations for optional sizes listed in the owner’s manual. The tire retailer’s hands are tied as there is no document to go to for suitable replacements.

We can talk around it all day, but, the bottom line is still going to be decided without official approval, unless the vehicle manufacturer gives their approval. It’s not the automotive industry folks, it’s the RV trailer industry without the foresight to develop a system for replacement tires comparable to - the one we are familiar with - the automotive industry.

How many trailer owners are out there riding around on unauthorized replacement tires that are also on the wrong rims with inadequate valve stems????

I cant leave this without saying something about tire warranties. They all view misapplication of their tires seriously and have made provisions in their warranty documents disallowing them. If they are that serious about it maybe we should take the time to read the warranty on all of our replacement tires. This is a common term used in most LT tire warranty documents as unacceptable for replacement tires: Improper application of tire size and/or specification.

[spock123]

I think the main thing is the ST tires will work but they are built in China which has a bad track record. The ST tires are a lot cheaper and manufacturers look at the bottom line.


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[youroo]

Originally Posted by Blackhat6mike

If there is no reason to not be allowed to use other typed tires, why rate them at all, unless they have different characteristics built in to address different needs? If this is true, couldn't you just run ST tires on your car of truck? Just curious?
Have you ever known of a wheel [rim] failing do to over inflation? I've yet to find anyone that has FIRSTHAND knowledge of such and not "I've heard of it happening". My humble tire guy [been in the tire business over 50 years with his family] said he never heard of it happening. My wheels aren't marked with psi rating either front or backside.

Well Mike check the Box that you Now Know someone 1st hand that had a Rim Failure! I wanted to put WIDE BF Goodrich TA Radial Snow Tires! In order to install on my Suburban they needed to be mounted on Offset Special Rims! Had special rims made through a Race Car Rim Mfg. they were Steel Rims,man did they look good mounted up and on the Truck! Off we go (8) guys inside and pulling a Double Deck Snowmobile trailer with (9) sleds! Snow and Ice covered roads northbound on I-75 for (580 miles)! 100 miles into the trip the Left rear Rim splits where the tire bead meets the rim,the tire Leaves the Rim,we are on what is left of the Rim! The Tire was not damaged at all? The Reese W/D helped save the Night! We pulled over and put on the Little spare! Then I went and bought (2 New Rims and Tires) to finish the Trip! Rim Mfg said I was Overloaded! Youroo!!

[GOTTOYS]

Originally Posted by spock123

I was going to buy a Cedar Creek 36CKTS, I have a 32RL now and I have Goodyear G614 on the camper now. What I was going to do was trade out the tires when I brought the bigger camper but I know I can't do that now. My tires are rated at 110lbs of pressure, is 3750lbs. That is 15,000lbs and that is great for my camper, GVWR, I think. My camper total weight of everything is 15,000lbs which will never happen. That's with all tanks full. The new camper is total weight 16,000lbs, so I will have to put Goodyear H rated tires on new camper and 17.5 tires. I think the new Cedar Creeks come with 17.5 ST tires made in China. I plan to stick with Goodyear tires that's made in America


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The 36ckts came with 16" Goodyear G614 tires as standard equipment until the 2016 models came out which is when they changed to the Chinese made Westlake tire, same size, same load range. There is no reason not to use the Goodyears on your your new trailer. It will have at least 20% of the total Gross weight carried by the pin just like other trailers. In the case of the 36CKTS that would be about 3200# Leaving 12,800 to be carried by the tires. All manufacturers do the same thing...

[spock123]

Originally Posted by GOTTOYS

The 36ckts came with 16" Goodyear G614 tires as standard equipment until the 2016 models came out which is when they changed to the Chinese made Westlake tire, same size, same load range. There is no reason not to use the Goodyears on your your new trailer. It will have at least 20% of the total Gross weight carried by the pin just like other trailers. In the case of the 36CKTS that would be about 3200# Leaving 12,800 to be carried by the tires. All manufacturers do the same thing...

The Cedar Creek 36CKTS now come with 17.5 tires, my Goodyear G614 are 16 tires.


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[Airdale]

Originally Posted by GOTTOYS

The 36ckts came with 16" Goodyear G614 tires as standard equipment until the 2016 models came out which is when they changed to the Chinese made Westlake tire, same size, same load range. There is no reason not to use the Goodyears on your your new trailer. It will have at least 20% of the total Gross weight carried by the pin just like other trailers. In the case of the 36CKTS that would be about 3200# Leaving 12,800 to be carried by the tires. All manufacturers do the same thing...

What manufacturers are you speaking for? All RV trailer manufacturers must fit tires to a specific figure. It’s called the GAWR and each axle has one. The amount of load for each one of them is found on the certification label.

Attached is a spec sheet for Westlake provided tires. I don't see one like the G614. They do have the new ST235/85R16G rated at 4080# at 110 psi.

http://lionshead.digitalhill.com/med...lake-Specs.pdf

Hmm, green valve caps. Lionshead must be using 100% nitrogen. And, red and yellow dots for optimum tire weight distribution to the rim.

[spock123]

I would have to move up to the H 17.5 Goodyear on the Cedar Creek. I'll not put China tires on another camper


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[Tireman9]

Will try and answer question posed in Posts 191 - 193

The different types of tires do have different requirements and as such that is why you end up with different load & inflation characteristics for tires with the same physical dimensions.
The key part of my post #190 pointed out "as long as the new tire at its inflation has equal or greater load capacity to the OE tire at its inflation and the max inflation capability as identified by the wheel manufacturer is not exceeded"

RE Rim failure due to over-inflation. While I was not present in the test chamber at the moment of failure, I have seen a few rims that did fail due to running higher pressure. Wonder if Youroo can tell us what state the Rim Mfg was from so we can all avoid any rimes made in that state.

RE Federal regulations
These apply to the manufacturer and in the US not to the owner. The issue of the standard is primarily based on the load capability of the tires being equal or greater than the GAWR. This is seen in the TT where a 7,000# axle is rated with GAWR of 6,500# because that is all the tires the RV MFG has selected will support. The reason for the wording in the owners manual is because telling owners to use the same as original is easier than offering instructions that need to be followed to learn what alternatives may also be acceptable. Just because you found no tire with identical load capability does not mean there are not tires with greater capacity. While some may also require a wheel change, I can easily identify dozens of tire options.

RE China made
I have written extensively on this in my blog on RV Tire Safety. We need to remember it is the consumer that is pushing the purchase decision on the RV MFG to get the lowest cost and to meet that goal the RV MFG buys the lowest cost option available to them.

[Airdale]

I’m going to present this from what I consider a typical manufacturer does when building a model trailer to a specific marketing tool. In this case the market target is for one half ton trucks.

The plans are drawn-up for 17 travel trailers and 6 fifth wheel trailers with the same brand name, all targeted for the ½ ton truck. The travel trailers start with a GVWR of 6400# and work their way up to 9000#. Every one of them are fitted with ST225/75R15D tires. The fifth wheels start with a GVWR of 9662# and work up to 10370# all with ST225/75R15D tires.

That production line can order all wheel/tire assemblies the same size for every unit. Setting GVWR, GAWR and selecting appropriate tire and rim sizes with recommended inflation pressures suitable for each fitment is part of vehicle certification. The minimum values and measurements are a product of NHTSA standards and regulations.

Consumers unhappy with minimum product values and specifications often point their finger in the wrong direction. When the value and measurements of things certified to be appropriate produce unacceptable results the standards which produced the results must first be scrutinized.