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Old 06-12-2012, 02:16 PM   #41
CWtheMan
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Quote:
Originally Posted by seahunter View Post
CW,

I respectfully disagree. That is what a "Load Inflation Table" is for. In my case I do not need to run my tires at 110 psi if I am not fully loaded. In fact, if I run them at full load (3,750 X 4 = 15,000 pounds) I would exceed my particular axle weight rating.

I submit this link:

http://www.goodyearrvtires.com/tire-selector.aspx

and then hit "Download Load Inflation Table"

to show the various tire load limits based on psi.
I’m sorry for the bluntness of this answer.

Load inflation charts are a product of the freedom of posting non confidential information on the internet.

Load inflation charts provide the information necessary for experienced and certified mechanics to apply them.

The first rule in the application of load inflation charts with regards to Original Equipment RV trailer tires is to NEVER use less air pressure than recommended by the vehicle manufacturer.

When replacing OE tires with tires that deviate in pressure/load requirements the minimum load requirement must be equal to or greater than the OE tires. From that load requirement a new recommended tire pressure is established and displayed near the OE placard (s).

CW

p.s. I have a couple of valid references to support those statements if needed. I hate to post them because they are lengthy and often quoted out of context.
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Old 06-12-2012, 03:05 PM   #42
seahunter
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Two Different Topics?

Quote:
Originally Posted by CWtheMan View Post
I’m sorry for the bluntness of this answer.

Load inflation charts are a product of the freedom of posting non confidential information on the internet.

Load inflation charts provide the information necessary for experienced and certified mechanics to apply them.

The first rule in the application of load inflation charts with regards to Original Equipment RV trailer tires is to NEVER use less air pressure than recommended by the vehicle manufacturer.

When replacing OE tires with tires that deviate in pressure/load requirements the minimum load requirement must be equal to or greater than the OE tires. From that load requirement a new recommended tire pressure is established and displayed near the OE placard (s).

CW

p.s. I have a couple of valid references to support those statements if needed. I hate to post them because they are lengthy and often quoted out of context.
Hi CW,

I think we may be looking at two different topics now. Your reply discusses the proper way to replace an OEM tire, and the other topic is whether that given tire can operate at different pressures under different loads. The Goodyear site I reference above is a consumer website, not commercial. Montana delivers trailers with G614 tires on the unit I have ordered, so that is an allowable OEM tire. I could see a problem going "backwards" or downgrading from a G614 to a Marathon, so I understand what you are citing above. Given that a proper specification tire has been mounted, then the charts are showing what the different inflation values will yield for weight capacity. So, say I have two 7k pound axles. I only need to run my tires between 95 and 100 rather than the maximum of 110 psi because any higher and my trailer's maximum weight would be exceeded. The tire allows for this, so there is no need to run at 110 psi, but I can if I want to. I can't recall what the 80 psi ST Marathons are rated at, but as long as I am over that equivalent for the LT G614 (which is what you are saying ) then I am okay - say it's 85 or 90 psi or whatever. In any case it gives me an operating range of say 85 to 100 in my case.
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Old 06-12-2012, 06:47 PM   #43
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Quote:
Originally Posted by seahunter View Post
Hi CW,

I think we may be looking at two different topics now. Your reply discusses the proper way to replace an OEM tire, and the other topic is whether that given tire can operate at different pressures under different loads. The Goodyear site I reference above is a consumer website, not commercial. Montana delivers trailers with G614 tires on the unit I have ordered, so that is an allowable OEM tire. I could see a problem going "backwards" or downgrading from a G614 to a Marathon, so I understand what you are citing above. Given that a proper specification tire has been mounted, then the charts are showing what the different inflation values will yield for weight capacity. So, say I have two 7k pound axles. I only need to run my tires between 95 and 100 rather than the maximum of 110 psi because any higher and my trailer's maximum weight would be exceeded. The tire allows for this, so there is no need to run at 110 psi, but I can if I want to. I can't recall what the 80 psi ST Marathons are rated at, but as long as I am over that equivalent for the LT G614 (which is what you are saying ) then I am okay - say it's 85 or 90 psi or whatever. In any case it gives me an operating range of say 85 to 100 in my case.

The DOT regulation for tire fitment on RV trailers at the time of first sale is very direct. The tires on the trailer MUST match the description on the certification label/tire placard. Brand is not an issue. Size, load capacity and recommended tire pressure are the issue.

The dilemma is the load inflation chart. A very basic issue comes into play. Who sets tire pressure? The DOT says that responsibility belongs to the vehicle manufacturer. Therefore what the vehicle manufacturer has recommended on the placard is the minimum standard for that vehicle.

There is no OOPS allowed for the tire placard. It MUST be correct at the time of first sale. It protects both the buyer and seller. If replacement options are installed by the dealer before the sale date the dealer has the authority and responsibility to install a new placard. Even after the papers have been signed any installer has the responsibility to change (pen & ink) the information on the trailer and in the owner’s manual.

Now, if you have a trailer that came from the factory with 16” LRG tires and the placard depicts 16” LRE tires you have a situation that requires a RECALL for all like vehicles by that manufacturer. It has already happened for other Keystone trailers.

Here is a reference that clearly states not to use tire pressures below those recommended on the tire placard. Look on page two - "Find the recommended inflation pressure".

http://www.trucktires.com/bridgeston.../WeighForm.pdf

CW
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Old 06-12-2012, 07:25 PM   #44
seahunter
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Quote:
Originally Posted by CWtheMan View Post
The DOT regulation for tire fitment on RV trailers at the time of first sale is very direct. The tires on the trailer MUST match the description on the certification label/tire placard. Brand is not an issue. Size, load capacity and recommended tire pressure are the issue.

The dilemma is the load inflation chart. A very basic issue comes into play. Who sets tire pressure? The DOT says that responsibility belongs to the vehicle manufacturer. Therefore what the vehicle manufacturer has recommended on the placard is the minimum standard for that vehicle.

There is no OOPS allowed for the tire placard. It MUST be correct at the time of first sale. It protects both the buyer and seller. If replacement options are installed by the dealer before the sale date the dealer has the authority and responsibility to install a new placard. Even after the papers have been signed any installer has the responsibility to change (pen & ink) the information on the trailer and in the owner’s manual.

Now, if you have a trailer that came from the factory with 16” LRG tires and the placard depicts 16” LRE tires you have a situation that requires a RECALL for all like vehicles by that manufacturer. It has already happened for other Keystone trailers.

Here is a reference that clearly states not to use tire pressures below those recommended on the tire placard. Look on page two - "Find the recommended inflation pressure".

http://www.trucktires.com/bridgeston.../WeighForm.pdf

CW
Thanks CW,

I remember seeing this guide before. It will be interesting to make sure when we pick up the trailer that the tire installer has updated the placard. Once we have the trailer, I will be doing exactly what your reference states:

"Find the RECOMMENDED Inflation Pressure

Always determine correct tire inflation pressure based on actual loads on the tires. Use the tiremakers’ recommendations (which you will
find in load and inflation tables). Never use inflation pressures lower than those printed on the vehicle placard."

So lets say my trailer weight is 14,200 after taking off the pin weight. So 14,200 is on the two trailer axles. Take 14,200 divided by four (tires) equals 3,550 pounds per tire. Since they happen to be Goodyear, I go to their inflation table and find 3,550 and it says the inflation pressure is 100 psi per tire. That is what I can run them at, I don't need to inflate them to 110 psi - but I can if I want too.

So, we are assuming (ha) that the new placard will be correct, but the source you have given is exactly the way to figure out the recommended inflation pressure based on ACTUAL LOADS on the tires. I guess my only point being one needs to reference the placard, but also needs to calculate the actual load to know how to properly inflate the tires.

Greg
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