We have to shop for tires as one of our tires appears to have a hernia. We have a Jayco 31.5 BHDS 5er with GVWR 10,700. Currently, the tires are Goodyear Marathons ST225/75/15 D with each have a max load rating of 2540lbs. Well I did the math and that only equals 10,160.... so I'm about 540 lbs shy of the GVWR.
Is this because of the pin weigh distributed to the truck? School me please. Not sure if we should get he E rated tires, but then will the stock rims be able to hold the additional pressure? Help.
You are correct in they subtracted the pin weight. The tire weight rating SHOULD be equal IMO but it is not the norm. I am fortunate that my TT tires and axles are rated for the full weight of the trailer.
I agree that having the tires rated at the GVWR would be a great idea, and the axle weight is only going to be something between 8,000 and 9,000 when loaded fifth wheel is around 10,500 pounds GVWR.
But if you have a blowout, and put nearly 4,000 pounds of one side of the trailer onto one tire, you will surely damage the inner casing of the tire if you did not notice the blowout and kept driving a mile or more at freeway speeds. So having tires with a slightly higher rating is good insurance in my book.
Even if I did have a blowout, I am not really going to stop right away, especially if on a two lane highway, I will wait until a wide section of road that is somewhat straight, not a passing lane. So what if I destroy one bad tire and ruin that rim, I am not getting out on the road side of the trailer to change it on a blind curve, or at night. I can get a newer rim for $35 at a junkyard. Even new rims with tires mounted on them are fairly low cost here. ETrailer.com
So yes the factory did size the rims and tires correctly at around 2,500 pounds each for the expected maximum 5,000 pound axle load, that really should not be over 4,500 pounds per axle if you are not exceeding the GVWR, and might only be around 2,100 pounds on each tire in normal use without the trailer fully loaded.
Putting on tires with a higher load rating is a great idea. Did you ever watch the tires on a TT as it is going down the road. There is a lot of flexing going on as the TT moves up and down. Tires take a beating on a TT.
My 5'er has a gvwr of 12900, on 5200lb axles.
I had Firestone Transforce 235-85-16 E installed on it.
Its a little overkill as the tires are rated for 3042lb X 4= 12000,
but I have plenty of reserve capacity in them.
I also got a deal on them. Right at $600 installed
'06 Ram with a Cummins
Tuned w/ EFI-Live
'09 36MAX1 Carrilite
Me, Alie, and Salie