Tires for our fifth wheel.

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Sharshep

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Joined
Aug 21, 2018
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6
I notice that the new Artic Fox fifth wheels come with ST235/85 R16 load range G tires. Should I upgrade from load range E? No problems so far but I would welcome he extra insurance if warranted. I have gone from LT to ST tires. I last bought Goodyear Endurance but they do not manufacture them in load range G. Thank you.
 

grashley

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May 7, 2015
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Western Kentucky
What tires came on YOUR camper?  What is on the tire placard?  What is the GVWR on your camper?

If it came with Load range D, an upgrade to G would be extreme.  If it came with Load range E, why do you want to jump 2 steps?

My FW came with ST235/80R16 E, and I just bought 4 new ST235/85R 16 F.  On my rig, even loaded to GVWR, the tires are only at 75% load capacity.
 

FastEagle

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Jan 12, 2010
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614
Well, if you went from a LT235/85R16E to a ST235/85R16E you gained nearly 600# of load capacity per tire at 80 PSI.
 

Gary RV_Wizard

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Feb 2, 2005
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West Palm Beach, FL
What are the axle ratings (GAWR) and gross (GVWR) rating of YOUR trailer?  That determines the max tire loading and thus the size tire you need, whether you go for the minimum or something more.  The axles on a 5W carry 80% of the total trailer weight, so each tire needs to be rated to carry at least 20% of the GVWR (and more to get some safety margin and longer tire life). Measure that in lbs and compare to the max loading in lbs shown on the tire sidewall or tire spec sheets.

As FastEagle says, you already gained substantially when you switched from LT to ST.
 

longhaul

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Dec 21, 2008
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562
More capacity doesn't always = more reliability especially if the trailer sees lots of highway miles and long hard all day runs.
Reliability is about the tires quality and high miles and years of service record.
 

Gary RV_Wizard

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Indeed, there are many factors affecting reliability.  Since this discussion is about load ratings, the factor I was addressing here is the stress of operating at the outer limits of loading vs a more comfortable load, e.g. 80% of max vs 99% of max.  All other things being equal, the more lightly loaded tire will hold up longer.  Less heat stress is probably the major reason behind that.
 

Sharshep

Member
Joined
Aug 21, 2018
Posts
6
Thanks for all of your thoughtful replies. I now need to better understand the physics of axel loading it my fifth wheel.  There seem to be lots of web guidance there. Plus I need to find a scale to mass the trailer. But of course I am home and unloaded. I know I need to be careful with my weight on my 8k trips. I do try to purchase quality tires. I have only seen a couple of G rated tires and no F rated.
 

Senator

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Jun 14, 2014
Posts
244
Location
Eagan, MN
I put on Sailuns, all-steel radials.  Not a steel belt only on the tread, it has a complete wrap of steel belting.    14-ply.  Load range G.

The cost of upgrading the tire from E to G is negligible, and not much downside.
 

Gary RV_Wizard

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Feb 2, 2005
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West Palm Beach, FL
My advice is to select your tire capacity based on max axle loads (GAWR), shooting for 10%-20% greater than the axle rating (for the two tires, combined). That way you can be comfortable that the tires can handle anything the axle can do.  Weighing the rig when fully loaded assures you that you have not exceeded the axle GAWRs or the GVWR, but isn't necessary to select & purchase tires.  If your actual loaded weight exceeds the GVWR or GAWRs, you need to reduce the load regardless of what tires you have chosen.
 

longhaul

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Dec 21, 2008
Posts
562
Excellent advise on choosing the best tire load capacity and load ranges for a trailer.

For some reason lots of new trailer owners seem to think the higher the tire capacity the better preforming/longer lasting tire they will have.
Example is one owner with a 5th wheel trailer 6k axle and 2700-2800 load per tire bit into the bigger is better and went with 17.5" load range H tires at 6006 lbs per tire/120 psi.  He ran them at 80 psi per sticker.
He came back and complained of super hot running tires and a 10 -12 percent across the board mpg drop on his 3500 Ram/Cummins. More experienced members told him he over tired the trailer and run the H tires at 100-110 psi. No more hot running tires and he got his mpg back closer to what they were.
Later he sold the 17.5" tires and wheels to a horse hauler....and did what Gary suggested. He now had the all steel ply carcass commercial grade LT235/85-16 G Sailun S637 /3750 lb rating.....and reported better mpg than his OEM ST E tires plus very cool running tires.
The S637 Sailuns were first a LT class tire till high tariff rates on LT and P class tires forced them to redesignate them To a ST class tire.

 
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