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Open Roads Forum  >  Tech Issues

 > Revived Trailer Tire Thread (formerly on the 5th Wheel Forum

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flamingogal

Annapolis, MD

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Posted: 03/05/12 07:52am Link  |  Print  |  Notify Moderator

CapriRacer -

Thank you for the chart, I found it very informative. I'm still on the fence about which tires to purchase - G614's or LT's (Ribs, TA's etc). I have a 2010 Cameo 35SB3, GVWR 14999#. We have not weighed this vehicle. The OEM Duro's are going to the landfill, one has a blister on the inside.

We had plans to weigh the camper this spring but the blister was discovered after our last trip and now I'm not taking it out until we get some new rubber. So I'll have to decide without the scale info.

Thank you Everyone on this forum for the amazing amount of information you have provided and for the continuing education I'm afforded here.

Jeanne

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Laurel, MD

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Posted: 03/05/12 08:00am Link  |  Print  |  Notify Moderator

flamingogal wrote:

CapriRacer -

Thank you for the chart, I found it very informative. I'm still on the fence about which tires to purchase - G614's or LT's (Ribs, TA's etc). I have a 2010 Cameo 35SB3, GVWR 14999#. We have not weighed this vehicle. The OEM Duro's are going to the landfill, one has a blister on the inside.

We had plans to weigh the camper this spring but the blister was discovered after our last trip and now I'm not taking it out until we get some new rubber. So I'll have to decide without the scale info.

Thank you Everyone on this forum for the amazing amount of information you have provided and for the continuing education I'm afforded here.

Jeanne

You might consider putting the spare on and going to the scales anyway.


ERS

Tireman9

Akron, OH

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Posted: 03/05/12 08:42am Link  |  Print  |  Notify Moderator

Seems to be some slight confusion in terms.

Dual is when two tires are mounted on the same end of one axle. This gives a total of four tires on the one axle.

Tandem is when there are two axles spaced close together.

Most Class-C and Class-A RV have single axle, dual rear tires
A few very large Class-A have dual rear tires on a single axle plus a single axle "tag" to add load capacity. This would be a "tandem axle" setup with one axle being single and one dual.

The load reduction for "dual" application is seen in both LT and Heavy truck "TBR" size tire Load Inflation charts. Passenger tires do not have a "dual" load as they are not intended, designed or tested to be applied in dual application. ST tires in the Tire & Rim Association yearbook do show both single and dual loads.

I do not remember ever seeing an RV with Dual Tandem axles while most over the highway heavy truck trailers are dual tandem setup.

I have seen some construction flat bed trailers with dual tandem setup but do not know if they were ST or truck tires.

I do wish I could find the Goodyear publication which suggested a load reduction for tandem application of tires. The references so far simply pointed to other web pages that claimed there were GY documents but didn't point to the actual documents.

I for one would support such a load reduction. There is good science that would support that this reduction become part of the regulations and design standards. While RV manufacturers would of course object I doubt there would be any tire companies that would try and oppose such a change if the change were supported through mathamatical modeling.

I am trying to get access to the Finite Eliment software but I cannot afford to buy a copy $$$$ and cannot expect this program to be run by a major company that doesn't currently market ST tires unless I can sell the idea to them. Finding that Goodyear publication would make my job easier.

Francesca Knowles

Port Hadlock, Washington

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Posted: 03/05/12 09:10am Link  |  Print  |  Notify Moderator

Interesting LT tire load reduction in the federal rules Jminlin provided... It applies to vehicles OTHER THAN trailers. Does that mean that LT's can be used at 100% on a trailer, but not on a light truck????

DOT wrote:

S4.2.2.3
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.



" Not every mind that wanders is lost. " With apologies to J.R.R. Tolkien

ExRocketScientist

Laurel, MD

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Posted: 03/05/12 10:31am Link  |  Print  |  Notify Moderator

Francesca Knowles wrote:

Interesting LT tire load reduction in the federal rules Jminlin provided... It applies to vehicles OTHER THAN trailers. Does that mean that LT's can be used at 100% on a trailer, but not on a light truck????

DOT wrote:

S4.2.2.3
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

I interpret it to mean 100% on a trailer.

FastEagle

Taylors, SC

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Posted: 03/05/12 12:29pm Link  |  Print  |  Notify Moderator

Francesca Knowles wrote:

Interesting LT tire load reduction in the federal rules Jminlin provided... It applies to vehicles OTHER THAN trailers. Does that mean that LT's can be used at 100% on a trailer, but not on a light truck????

YES!

FE

DOT wrote:

S4.2.2.3
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.



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FastEagle

Taylors, SC

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Posted: 03/05/12 12:34pm Link  |  Print  |  Notify Moderator

On another note; Most LRD & LRE LT tires have a third steel belt. I don't recall that being mentioned in this thread. Advertisement says it's for puncture resistance.

FastEagle

p.s. Maxxis ST tires are the only one's I've found that have followed suit.

CapriRacer

Somewhere in the US

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Posted: 03/05/12 12:46pm Link  |  Print  |  Notify Moderator

FastEagle wrote:

On another note; Most LRD & LRE LT tires have a third steel belt. I don't recall that being mentioned in this thread. Advertisement says it's for puncture resistance.

FastEagle

p.s. Maxxis ST tires are the only one's I've found that have followed suit.


You may want to do a little research on that! LT tires rarely have 3 steel belts - and that would also be true for ST tires.


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CapriRacer

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sh410

Northwest

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Posted: 03/05/12 01:55pm Link  |  Print  |  Notify Moderator

From FE's post:

"GTW is what a trailer is supposed to weigh when delivered to the new owner. The CCC placard will list the maximum amount of cargo that can be added to the GTW. When added together those two cannot be more than the vehicle’s GVWR. At that point the only way to find the pin weight is to weigh it. Once the pin weight is deducted from the GTW the remainder - GAW - is what’s being carried by the axles. That weight cannot be more than the GAWR. OE tires must have a total load capacity equal to or greater than GAWR."

According to Dexter Axle:

"The maximum load carrying capacity is limited to the lowest load rating of any individual component selected. For instance, the load rating of a pair of wheels may be lower than the other axle components. If the is the case, the load rating of the total assembly must be reduced accordingly. As a specific example, if a pair of wheels are rated at 1500# each and are use with other components rated at 4000#, the maximum load capacity will be limited to 3000#. If two tires rated at 1400# each and are used on this assembly, then the maximum load carrying capacity is limited to 2800#"

Dexter applications manual

In example from placard you posted, according to Dexter the axles rating are derated to the total of load rating of the tires.

Can you post a reference that OE tires must have a total load capacity equal to or greater than GAWR?





NHIrish

White Mountains NH

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Posted: 03/05/12 01:56pm Link  |  Print  |  Notify Moderator

JIMNLIN wrote:

If the trailer is a dual tandam axle unit (8 tires) then the reduction in capacity applies in this case just like a dual wheel axle on a truck. The modern tandam axle trailer (4 tires) with a equilizer bar has no need of its tires load capacity to be derated.

Many boat trailers (and other single and tandam axle trailer types) come with P tires. Fed 571 regs says this about P tires capacity on a trailer:

"When a passenger car tire is installed on a multipurpose passenger vehicle, truck, bus, or trailer, the tire's load rating shall be reduced by dividing by 1.10 before calculating the sum ....(snip).

I can't see Goodyear adding another 12 percent reduction on top of the fed required 10 percent reduction on their tires. They couldn't compete with other tire makers for OEM tire replacemnet, if this was the case.


So I'm still unclear on whether we have a misinterpretation somewhere on tandem v. dual tire setup. Ref. the above quote is this just your thoughts or is this from a document somewhere.

Anyone have some real info on this HUGE issue. Based on the tires I see on new fifth wheels, I can't believe thay have to be derated! AND if they did, most of the heavy fifth wheels and trailers are out of spec right out of the gate.


2010 Carriage Cameo 32FWS
2011 Chevrolet 3500 DMAX ECLB
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