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Old 07-22-2015, 11:38 PM   #1
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Maxed out and overweight LR E tires - wmtire & Tireman9, ideas?

My fifth wheel has a gross weight of 15,825 lbs. and 7,000 pound axles.

I did an individual wheel weighing down in Florida and found that I'm at 3,400 pounds for 2 tires and 3,500 for another. (Strangely, the forth is at 2,950 lbs..) My current Maxxis m8008 tires have a maximum load carrying capacity of 3,420 lbs. in my size (235/80r16, lr E). (I replaced Akuret HF188 with a maximum load carrying capacity of 3,417 lbs.)

I think I could/should be increasing to a 17" wheel and going up to LR G. The the problem that I have is that I have extremely little space between the tires (less than 2").

We are definitely loaded heaviest in the back because of the dual opposing slides. Additionally, the back side from wheel well rearward is heavy (though, since we removed a sofa and changed stuff up- I question if it is that much different than previously).

Anyway, any tire ideas? I haven't had issues, just looking to consider options before being forced into a decision like last time (a nail in one tire and a bulge in another).
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Old 07-23-2015, 06:43 AM   #2
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Dang Doug, if those numbers are correct, you sure don't have much wiggle room in weight.

If you are wanting peace of mind in the numbers area, there are a few options, none of which are cheap.

Goodyear makes a 14 ply rated 235/85R16 tire that has a capacity of around 3,750 lbs per. The problem here, is that it runs at 110 psi and you might need new wheels to boot, to carry that kind of air pressure safely.

Utilizing your same wheels, you could shop around and find a tire like the Power King Towmax. According to it's specs, using the same size and psi tire you currently have... they rate theirs at 3520 lbs.

Moving up to a 235/85R16 in a Towmax, with the same 80 psi nets 3640.

The clearance between the tires may be problematic too. A 235/85R16 is about an inch difference of diameter from what you have currently. However, once you measure from the center of the hub, it works out to be 1/2 inch on top and a 1/2 inch on bottom...or the 1/2 inch front and rear of the tire, if you can picture what I'm saying.

Using a 235/85R16 is going to be 1/2 inch taller into your fender well, and make the TWO tires 1 inch closer together (1/2 inch per). It will also raise your trailer off the ground 1/2 inch....so you may have to step a little higher.

As far as the Power King Towmax, I have no recommendation on the brand itself. Research at your own risk.

Towmax STR II Tires | Own The Road

Carlisle sells ST tires with the same specs as the TowMax and even has a 12 ply rated 235/85R16 at 95 psi and 3950 lbs.

http://www.carlisletransportationpro...adial-trail-rh

Moral of the story is, there are different brands out there, with different capacities. You just have to look around and see what you want and feel comfortable using.
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Old 07-23-2015, 09:35 AM   #3
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I'm not totally against getting new wheels, though I do know that essentially doubles+ the price. My biggest problem is the clearance between the wheels. It's really cozy now. Any idea how much is the minimum there? I have the clearance above the tire, just not between them.

To find the maximum PSI of the tire, have I read that it's stamped on the wheel itself somewhere?

The other side of things, I know the ST vs. LT tire is heavily debated. Honestly, I'm falling on the side of being open to LT tires but don't know that I have the spacing for them.
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Old 07-23-2015, 03:40 PM   #4
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As for the tire weights. I need to pull my CAT scale tickets to verify the numbers from the individual wheel weights, but it seems legit:

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Old 07-23-2015, 03:54 PM   #5
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Originally Posted by ependydad View Post
I'm not totally against getting new wheels, though I do know that essentially doubles+ the price. My biggest problem is the clearance between the wheels. It's really cozy now. Any idea how much is the minimum there? I have the clearance above the tire, just not between them.
In the reference provided below Dexter says 1" minimum, item #24.

http://www.dexteraxle.com/running_gear_tips
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Old 07-23-2015, 03:57 PM   #6
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In the reference provided below Dexter says 1" minimum, item #24.

http://www.dexteraxle.com/running_gear_tips

Quote:
Tip #24: Axles should be spaced far enough apart to allow a minimum of 1" clearance between the tires. More space would be required if tire chains are to be used.
Thanks!
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Old 07-23-2015, 04:23 PM   #7
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Originally Posted by ependydad View Post

Anyway, any tire ideas? I haven't had issues, just looking to consider options before being forced into a decision like last time (a nail in one tire and a bulge in another).
Your current tires should have a diameter of about 30.8 . The diameter of the GY G614 is about 30.7 Other name brands will have very similar figures. However, the G614 or any others like it will require 16x6.5 high pressure rims rated for 3750# at 110 psi.
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Old 07-23-2015, 04:23 PM   #8
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There was a recent post on a Fulltime RVing group on Facebook about this basic topic- blowouts of ST tires on heavy rigs. In it, a commenter was an advocate of going to 17.5" wheels and jumping to an H-rated LT tire. In it, he says:
Quote:
Originally Posted by If it's on the internet, it must be true
So, if you want to safely support the weight of your trailer AND roll down the road, you need 17.5" rim hardware and 16 ply "H" ratings on your tires.

"H" rated tires have less sidewall height, stronger internal construction, take up to 125 psi cold and will roll happy as a clam all day and night @ 130-140 psi hot. On our 16K GVWR trailer, I only need to fill to 115 psi cold to meet my weight specs, so we have major additional headroom there.

And yes, they will fit in your wheel wells and won't rub. This is why: 215/75R17.5 is about 1/2" smaller diameter than the OEM 235/85/16 size. Shorter sidewall on a bigger rim as I mentioned equals roughly the OD you started with.
In talking to wmtire via PMs, he provided this equation to figure out outer diameter of wheel + tire:
Quote:
Originally Posted by Private PM that should never be shared
There is a formula for approximating different total tire size diameters (with rim).

Section width X aspect ratio X 2 = n

take n and divide it by 2540 then add to rim diameter......and you have the approximate tire and rim diameter together.
To test the Facebook commenter's comments, I did the math:
So, for 215/75r17.5 it's... 215 * 75 * 2 = 32,250. (32,250 / 2540) + 17.5 = 30.2".

My current tire is ST235/80R-16E1 which works out to (37,600 / 2540) + 16 = 30.8".
Sure enough, new H-rated LT tires are about 1/2" smaller in diameter than my current tire.

The problem is, it's new wheels, tires, about $2,000, the whole 9 yards. And, it reignites the ST vs. LT tire debate. (But, I do know some higher end/heavy/fulltiming units are already coming with LT tires stock; so it makes me feel a little better.)
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Old 07-23-2015, 04:24 PM   #9
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Your current tires should have a diameter of about 30.8 . The diameter of the GY G614 is about 30.7 Other name brands will have very similar figures. However, the G614 or any others like it will require 16x6.5 high pressure rims rated for 3750# at 110 psi.
Remind me again how I find out if my rims will support the higher PSI?
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Old 07-23-2015, 04:32 PM   #10
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Remind me again how I find out if my rims will support the higher PSI?
Some of their manufacturers put those specs on the rim, maybe front or back and even under the tire. However it's not a DOT requirement to do so.

The best answer will come from the rim manufacturer. They are required to put their identification on each individual rim along with it's serial number and part number. A call or email to them with that information will get what you're looking for.
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