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Author Topic: Rating of tires for 5th wheels  (Read 235 times)

lmphil42420

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Rating of tires for 5th wheels
« on: July 20, 2017, 01:57:13 AM »
Hi all
I am a little confused.  I have been an RV owner for many year probably close to 20 + years.  I just bought a 2014 Jayco Eagle 28.5 RLTS the dry weight of the coach is around 8300 to 8400 lbs with a max GVWR of 10500.  The problem that I am having is that the coach has 225ST 75R 15 "D" rated tires.  the side wall indicates single axle max weight is 2590lbs and dual axle max weight is 2200lbs.  This coach is dual axle, so doing the quick math I count 8800lbs as the max load for this coach leaving me well short of the 10500 GVWR.  So I point this out to the gentleman who is performing the walkaround with me.  So we go and see the sales manager and he does his due diligence and contacts the manufacture.  He breaks out the specification for the coach and shows me that the coach came from the manufacture with those tires.  I disagree with him and tell him it is a safety issue.  He said that if it comes from the manufacture that way we do not change anything.  So here is my dilemma as I understand tire ratings this rig based on the weights on the side walls of the tires I am grossly overweight and the coach should have at a minimum and "E" rated tire.  Am I thinking correctly??

xrated

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Re: Rating of tires for 5th wheels
« Reply #1 on: July 20, 2017, 05:53:13 AM »
No!  That reference to single or dual setup is in reference to using two tires on the same axle on the same side.  Think Dually trucks....not tandem axle trailers.
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kdbgoat

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Re: Rating of tires for 5th wheels
« Reply #2 on: July 20, 2017, 06:01:32 AM »
The manufacturer's also don't have to have the tires/axles/suspension rated to carry the full 10,500#. One must remember that generally, on a bumper pull, 10 to 15% of the trailer weight is at the tongue and and is being carried by the tow vehicle. On a fiver, 20 to 25% of the fivers weight is carried by the tow vehicle. Since the tongue/pin weight is not carried by the trailer's tires, the tires aren't required to be rated for the full GVWR of the trailer.
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Rene T

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Re: Rating of tires for 5th wheels
« Reply #3 on: July 20, 2017, 07:32:46 AM »
Welcome to the forum.
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Gary RV_Wizard

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Re: Rating of tires for 5th wheels
« Reply #4 on: July 20, 2017, 08:40:01 AM »
Federal safety standards require that 5W trailer axles & tires be rated at least 80% of the trailer GVWR, so 8400 lbs in your case. The 2200 lbs is [just] adequate in that case. However, xrated is correct that the "dual" load rating does not apply except where the tires are mounted in "dually" pairs, i.e.two tires/wheels mounted on one hub. Your trailer axles are singles, no matter how many  axles you have. The 2590 load rating applies, so you are actually in excellent shape, with 10,360 lbs of capacity at max psi. That's better than the OEM tires on the vast majority of trailers.
« Last Edit: July 20, 2017, 08:41:41 AM by Gary RV_Wizard »
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FastEagle

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Re: Rating of tires for 5th wheels
« Reply #5 on: July 20, 2017, 11:52:49 AM »
All ST225/75R15D tires have a maximum load capacity of 2540# at 65 PSI. Maybe you misread the sidewall information. If not, report the discrepancy to NHTSA.
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Lynx0849

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Re: Rating of tires for 5th wheels
« Reply #6 on: July 20, 2017, 12:52:17 PM »
No!  That reference to single or dual setup is in reference to using two tires on the same axle on the same side.  Think Dually trucks....not tandem axle trailers.

To clarify for those who may not know...

The reason for lower ratings for dual wheels is that they can't cool as well as a single.

xrated

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Re: Rating of tires for 5th wheels
« Reply #7 on: July 20, 2017, 02:44:18 PM »
To clarify for those who may not know...

The reason for lower ratings for dual wheels is that they can't cool as well as a single.

Thank you for posting that info....I didn't know.  I've only had a Dually since early June.  I knew about the "De-rating" but didn't know why.
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FastEagle

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Re: Rating of tires for 5th wheels
« Reply #8 on: July 20, 2017, 07:24:00 PM »
Dual tires are subjected to more severe operating conditions, such as:

High heat exposure, due to close proximity to brakes

Lower air circulation to assist in cooling

Crowned road surfaces (which can cause inside dual tires to support more of the load than the outside dual tires).

So,  Derating has been standardized for those tires.

Reference: RMA
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