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Old 04-03-2015, 07:53 PM   #1
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How to determine which tire by weight?

My 2011 Cougar 246RL is at the point where I'd like to replace the tires. I don't have it here (it's at the dealer 'til Monday), but I did a search in here and found a TON of discussions about trailer tires. Most discussions are about trailers a lot bigger and heavier than ours, so I'm trying to understand how tires are sized...

My 246RL SAYS:

Dry weight 6810 lbs
Capacity 2190 lbs
hitch weight 1450 lbs
47 gal fresh water
28 gal black water
56 gal grey water
60 lbs propane

So, my total weight at capacity would be 9000 lbs, right?

I DON'T have a scale handy to weigh the trailer and I'm trying to figure out a reasonable weight for tires...

Presuming we're traveling with the fresh water full, black 1/2 full and grey half full, and the propane full, that'd be 47+14+28 @8.35 lbs/gal = ~750 lbs. Another 60 for propane and we've got ~810 pounds.
Figure a fridge full of food, a pantry full of dry goods, soda, juices, and so on, and I've gotta figure 200 - 300 pounds of edibles.
Add clothes for all FOUR seasons for two, and again I figure another 200-300 lbs.
Tools, spares, sundry junk, laptops, tablets and all the other stuff we travel with including recumbents in the pass-through, and I've gotta figure another 300-500 lbs.

Based on all that, I figure we've got to have somewhere around 800+300+300+500 lbs, so around 1900 pounds of that 2190 capacity...

Does all that seem reasonable in terms of figuring we're a lot closer to 9000 pounds than 7000?

When the trailer spec says 1450 pounds on the hitch, is that when evenly loaded to 9000 pounds? Or is that when the trailer is empty at 6810 pounds?

Anyhow, in my example, if I take the 9000 lbs (just to be safe), and subtract the 1450 hitch weight leaving 7550 on the axles, can I PRESUME it's reasonably evenly loaded on each axle and on each side? If so, I'd have approximately 1900 lbs on each tire.

It comes with 225/75R15D tires that run at 65 lbs and are rated at 2540 lbs (again, this is from memory). Based on that, don't I have at least a 20% reserve on each tire in terms of load? Is it a valid assumption that the loads are relatively even or do trailers routinely have one side MUCH heavier than the other?

So, my bottom question is should I stay with the 225/75R15D at 2540/tire or got a 225/75R15E that's rated at 2830/tire?

I don't have a lot of choices in trailer tires here - it looks like I can get either Marathons or Towmax locally. I MAY be able to get Carlisles.

I saw all the entries about rib tires and other hugely expensive truck tires, but that seem like drastic overkill for a 27' trailer. Unlike the much larger trailers in the discussions, is it worthwhile to switch form ST tires to LT tires for my smaller trailer? If so, do I just get lt tires with a capacity of at least 2540 like the Ds that are on there? Since the Ds are 8-ply, do I need to get 8-ply LT tires or just LT tires with a high enough load rating?
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Old 04-03-2015, 08:03 PM   #2
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The only way to know for certain about the weight is to weigh the trailer. IF your rims are rated for the pressure you can run E rated tires, but most trailers that come with D rated tires are not rated for the higher pressure E rated tires. You can also get Maxxis tires reasonably here: Lowest prices for Maxxis Trailer tires - SimpleTire.com I got mine there and was treated quite well.
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Old 04-03-2015, 08:08 PM   #3
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I would recommend getting better tires with more capacity then the factory installed tires. Moving up from 'D' to 'E' tires makes sense to me and would be a good 1st step.

I am a firm believer that LT tires are built to better tolerances than ST tires. I have never had a blow out on an LT tire but have had 3 blow outs on ST tires. If you can find an LT tire with enough load capacity that would be an optimum upgrade. Else move up to 'E' capacity.
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Old 04-03-2015, 10:39 PM   #4
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9000lb gross = 1800lb pin weight (+/-) 9000 - 1800 = 7200lbs on axles / 4 wheels =
about 1800lbs on each tire. 20% over capacity would mean you should shoot for a tire that will carry 2160lbs at max load rating. The Ds should do it, but I would go for the Es if the rim will handle the pressure.
Any lesser loading of the trailer would make it easier on the tires.
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Old 04-04-2015, 05:47 AM   #5
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Thanks for the replies... Does the 1800 lb pin weight mean the 1450 is when the trailer is dry and empty?

We MAY not have as much stuff in the trailer as I suspect, but there may also be times when the black and gray water tanks are more than half full (not often, but I suspect it may happen occasionally), so I figured it was better to think heavier than lighter...

I never thought about the wheels not being able to handle the 85 psi tire pressure. How would I find that out? I know they're chrome wheels, but is there some indicator on them about the maximum pressure they'll handle?

It may be academic actually 'cause when I went out to find 15" LT tires I found almost none - I think maybe 1 or 2, but the vast majority of lt tires were 16" and larger than 225 - certainly those with a rating of at least 2500 lbs. That would be a problem 'cause I don't want a larger tire that would raise the trailer any higher.

I have no objection to going to LT tires but I wouldn't want to have some unusual orphan size that would be a pain to replace on the road if needed - it looks to me like a 225 15" lt tire would fall into that category.

I looked at simple tire and it appears that in ST tires the carlisle and maxxis are within a few dollars of what the marathons and towmax I can get locally would cost so there's no big cost difference either way.

As for weighing - question of the morning - HOW does one get their trailer weighed? Are there scales at truck stops or some other place? Am I correct that I weigh truck and trailer, then pull the truck off the scale to weigh trailer than subtract trailer from total to get pin weight? Do you try to weigh just one axle to see if the axles are different or does that matter? Same thing with one side to see if they're different?
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Old 04-04-2015, 06:29 AM   #6
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Quote:
Originally Posted by dkperez View Post
...As for weighing - question of the morning - HOW does one get their trailer weighed? Are there scales at truck stops or some other place? Am I correct that I weigh truck and trailer, then pull the truck off the scale to weigh trailer than subtract trailer from total to get pin weight? Do you try to weigh just one axle to see if the axles are different or does that matter? Same thing with one side to see if they're different?
The best way is to weigh each wheel separately. Also weigh the tow vehicle hitched and unhitched so you can calculate the hitch weight.

RVSEF is one organization that weighs each wheel. They usually have someone at larger RV rallies to do this. Escapees SmartWeigh is another program. They do weights in TX, AZ and FL if you're anywhere near those areas and also at their rallies.

Given that it may be hard to find a place to weigh each wheel, most truck stops have a CAT scale that will give you weights by axle, which is the next best option. The cost is usually around $10. Stop on the scale with the trailer axles on different segments of the scale and with the TV on a different segment. Drop the trailer and drive the TV back onto the scale and weigh unhitched to calculate hitch weight.
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Old 04-04-2015, 06:58 AM   #7
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You could replace your tires with LT/E rated tires, but they're not easy to find in 15" sizes. Most high quality LT/E ribbed tires going on fifth wheels are 16" sizes.

You'd probably be best served just putting Maxxis M8008's on your trailer. Forget about any of the Chinese tires of any brand--including Goodyear Marathons. They're easily found at online tire sources, and are fine trailer tires.
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Old 04-04-2015, 10:25 AM   #8
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Go to US Made "E" tires and use the weight/inflation chart and add 5psi.
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Old 04-04-2015, 12:34 PM   #9
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You don't even have to unhitch at a CAT scale if you position the truck and trailer correctly--truck front axle on front segment, rear axle on 2nd segment. trailer on 3rd segment so the landing gear just will fit on the 3rd segment also. Before pulling on scales, go inside and tell clerk you want two weights without driving off the scales. (All this is easy if there isn't a lot of truck activity at the scales--look for one as you travel that isn't busy) Then drive on scale and position everything as mentioned--get a weight reading, then raise the trailer til you see that the pin is lifting off the hitch, but don't lift so much the truck is being raised. Get a second weight, drive off and go to clerk for the readings. The difference in the truck rear axle/trailer weight readings will be the pin weight.
Be careful around the scale edges if it is elevated......
Joe
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Old 04-04-2015, 09:48 PM   #10
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Cool... I'll have to see if I can weigh sometime.

I'll probably stay with the load range D tires for this pass. BUT, how DO I find out whether the rims can take the higher pressure of the E tires?
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Old 04-04-2015, 10:12 PM   #11
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Some rims are marked on the inside of the wheel, others inside the tire itself. Not all are marked as to PSI. Usually, they are made for 65-then 80- then 120psi tires.
When you have a tire dismounted, take a look all over/inside the rim for any markings.
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Old 04-05-2015, 01:11 AM   #12
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Originally Posted by dkperez View Post
Cool... I'll have to see if I can weigh sometime.

I'll probably stay with the load range D tires for this pass. BUT, how DO I find out whether the rims can take the higher pressure of the E tires?
Look on the rim for the manufacturer's name. Get the rim model number and email or call them.

Many of the individual rim manufacturers have rim information in PDF files on the internet.

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Old 04-05-2015, 08:08 AM   #13
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Last year I switched to LT Tires. Just had two many problems with the ST tires on both of the fifth wheels that we have owned. I selected Toyo E rated for my 5er. The side wall pressure is rated at 80 PSI and I always run 80 PSI. I also have a pressure pro TMS installed, and have had it for several years. Great to know your pressure on each tire, when ever you want it.


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Old 04-06-2015, 02:07 PM   #14
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Maxxim makes a good trl tire for tje weifht you l wouldn't bother with the expense of an LT tire. JMO
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