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Old 06-03-2020, 12:12 AM   #41
CalandLinda
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Attn: Anatnom and others this msg. may affect.

Being in the quarantine mode I have oodles of time to ponder tire situations. I’ve been writing about RV trailer tires for about 16 years. I belong to a half dozen trailer forums or those that have trailers. I use other nick names in some of them. I first joined here as FastEagle but was dismissed because I didn’t own a Montana. Later when that membership rule was modified we rejoined. We have a 38’ Everest which is very similar to the Montana and built by Keystone. Back in its “hay-day” it was one of the largest Keystone fivers being built.

Anyhow, the original tires on our trailer got me into researching ST tires. Why? Within the first year we lost every one of the OE tires to tread separations. Why? We exceeded their speed restriction & they were always close to being overloaded, in fact we probably always had at least one tire position extremely overloaded. Their speed restriction was 65 MPH. The tires were rated at 3000# and the axles were vehicle certified at 6000#. They were USA built GY Marathons.

The ST235/80R16 LRE has been manufactured with three different maximum load capacities; 3420#, 3500# and 3520#. The GY Marathons and the new GY Endurance in that designated size and load range has a maximum load capacity of 3420# at 80 PSI. It’s always been a problem tire for Keystone or others that want (ed) to use them on 7000# axles. Keystone, like all other trailer manufacturers, quickly found-out that they would have to recall any of those GY tires installed on 7000# vehicle certified axles.

That brings me to ANATNOM’s situation. Because trailer manufacturers have the authority to set GAWR values, they solved their GY LRE Marathon tires on 7000# axles by devaluating the axles to 6750# and certified them at that value. Still they didn’t have hardly any load capacity reserves and would surely fail earlier than expected, especially when operating at the certified GAWRs maximum load capacity.

Fast forward. RVIA, with all their wisdom, mandated a minimum tire load capacity reserve recommendation (10%) for all participation members – about 98 % of the RV trailer manufacturers.

Bottom line; The minimum acceptable load capacity for vehicle certified 6750# GAWR axles is about 3715#. None of the ST235/80R16 or ST235/85R16 LRE tires qualify.

NOTES: The only tire brand that has not officially increased their ST tire speed ratings to 75 MPH or above is Maxxis. – The GY Endurance is not yet going to China. They are moving it from their AL plant to a NC plant.
 
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Old 06-03-2020, 06:55 AM   #42
Joe in Texas
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Thank you.....for the numbers and history behind them.

Bottom line- sailun S637 -235/85R16 - is that the tire time buy ? For my 2011 - Montana........
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Old 06-03-2020, 08:04 AM   #43
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Thank you.....for the numbers and history behind them.

Bottom line- sailun S637 -235/85R16 - is that the tire time buy ? For my 2011 - Montana........

Its the choice of many on here, including me. IMO you can'y buy a better G rated tire for your fifth wheel. Yes they are made in China, I got grief from my wife buying them, but the bottom line is I wanted the best tire to put on our fifth wheel.

This forum has been pretty civilized as far as where the tire is made, most forums you will get a couple guys who condemn anyone buying Sailuns, and are probably typing away on a computer made in China, while wearing a shirt ,and pants also made in China, but thats how it goes. Good luck on your tire choices
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Old 06-03-2020, 03:12 PM   #44
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Originally Posted by Joe in Texas View Post
Thank you.....for the numbers and history behind them.

Bottom line- Sailun S637 -235/85R16 - is that the tire time buy ? For my 2011 - Montana.....
The proper nomenclature for that tire is ST235/85R16. Brands are not linked to tire sizes.

The official load capacity designator for ST tires is the load range letter system.
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Old 06-04-2020, 10:40 AM   #45
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Originally Posted by CalandLinda View Post
The proper nomenclature for that tire is ST235/85R16. Brands are not linked to tire sizes.

The official load capacity designator for ST tires is the load range letter system.
I too am getting ready to order the Sailun's to replace the Marathon's on our new to us 2012 3750FL. The Marathons are ST235/80R/16 and wondering if the Sailun ST235/85R/16's would be better than matching the original radius of the Marathons? What are the advantages?

I was going to keep the Marathon for a spare but am questioning myself on that as well. Is the spare tire rim also rated for the increase in PSI?

Thanks,

Phil
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Old 06-04-2020, 03:46 PM   #46
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I too am getting ready to order the Sailun's to replace the Marathon's on our new to us 2012 3750FL. The Marathons are ST235/80R/16 and wondering if the Sailun ST235/85R/16's would be better than matching the original radius of the Marathons? What are the advantages?

I was going to keep the Marathon for a spare but am questioning myself on that as well. Is the spare tire rim also rated for the increase in PSI?

Thanks,

Phil
The ST235/80R16 LRG is the best fit because it has the same profile as the Marathons.

The spare tire does not have to be the same size and load range as the running tires. It just has to have a load capacity that equals the load capacity of the vehicle certified GAWRs. It's really an emergency service tire.
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Old 06-04-2020, 03:52 PM   #47
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The 235/85/16 tires are slightly taller and wider. You can stay with the same size tire or go to the slightly larger tire. The 80 series are rated at 4080 pounds and the 85 series are rated at 4400 pounds. Either tire is rated for more than your wheels. You should be able to use the same tire for the spare and i would buy 5 tires as the spare marathon is getting old and you may just have another flat if you needed it in an emergency. I would probably just buy the tire that is the cheapest at the time of purchase. Simple Tire varies on the price of these tires day to day. You can't make a wrong decision on either tire.
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Old 06-04-2020, 04:20 PM   #48
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I recently upgraded to Sailun's a few weeks ago. I decided to go with the taller 85's profile tires instead of the original 80. I also upgraded the spare tire to the taller 85 profile; if not, the diameter of the spare would be different from the other tires. While it probably would still work, I decided not to risk it and change a 2 year old never used spare 80 profile tire to the taller 85 Sailun. My vanilla spare rim was rated for 110 PSI. Be prepared to use a hydraulic jack to mount the spare back up under the trailer - Holy cow that Sailun tire is heavy! My reasoning for going with the taller tire was to help level my trailer when on the truck. My truck sits tall in the rear and made my trailer sit a higher in the front. While the 85's only raised the trailer a little over 1/2", it was enough to make a difference - trailer looks level now with the truck. One challenge I did run into with the taller tire was rub on a wheel skirt. For some reason, my left side (big slide) tire skirt is offset more to the front of the wheels than on the right side (I suspect this for allowing more access space for the rear gray water dump valve via the front of the wheel skirt). When mounting the 85's, the rear left wheel rubbed the wheel skirt, so I trimmed the inside of wheel skirt (3/8" hardly noticeable). I'm really glad that I made this investment in quality tires; the trailer handles / rides much nicer and I have improved piece of mind when towing.
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Old 06-04-2020, 06:55 PM   #49
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this is a good tread to read at bedtime
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Old 06-04-2020, 07:36 PM   #50
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I'm just wondering about the weight of the Sailun's for the spare tire holder. Is the cable and the rack strong enough to hold it up. I just replaced all 5 of my tires with Sailun's
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Old 06-04-2020, 08:49 PM   #51
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I'm just wondering about the weight of the Sailun's for the spare tire holder. Is the cable and the rack strong enough to hold it up. I just replaced all 5 of my tires with Sailun's
My 2012 has supported a GY G614 and now Sailun G637 (both of which weigh about the same) spare for the last 8 years and 60,000 miles. No problems yet.
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Old 06-05-2020, 01:00 AM   #52
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I weighed on a digital scale the e-rated tire and the g-rated tire and the g-rated tire weighed twice as much at 63 pounds as the e-rated tire. I've had the g-rated spare for 5 years and i don't think you will have any problem. If you are concerned then you could install a strap across the spare for peace of mind.
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Old 06-05-2020, 02:16 PM   #53
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Just maybe the vehicle manufacturer is doing the right thing by using the ST235/80R16 vice the ST235/85R16; because the latter is wider and more susceptible to damages from interplay sheer.

I'd be surprised if they would recommend the 85s over OE 80s.
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Old 06-06-2020, 11:01 PM   #54
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You are correct, they used to be an extra cost option on Montanas. Then RVIA (or somebody) moved the goal posts. No longer do the tires just have to exceed the axle rating, they have to exceed it by 10%. So a 7,000 lb. rated axle needs tire capacity of 7,700 / 2 lbs (i.e. each tire rated at 3850 lbs). The GY G614 is a Load Range 126 or 3748 lb. tire, just short of the 10% requirement. Hence the Sailuns became the standard.
We got our 3791 just when that new RVIA rating changed and it came with the Sailun 637 ST235/80R16 rated at 4050#. My question has always been why are the rims rated at 3750#? When I replace, I want to go with higher rated rims (17.5") and the appropriate tire.
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Old 06-06-2020, 11:16 PM   #55
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Although they are out of stock, I see Speedy Tire has the best price?!!
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Old 06-07-2020, 09:58 AM   #56
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Originally Posted by DanandBrenda View Post
I'm just wondering about the weight of the Sailun's for the spare tire holder. Is the cable and the rack strong enough to hold it up. I just replaced all 5 of my tires with Sailun's

I had several hundred miles on my 2008 Montana without a problem with the cable system, but it did give me concern. If I would kept the fifth wheel I would of done something at the least a ratchet strap for extra support.

With this new fifth wheel it has a slide out rack, no cables, very easy to remove the spare , nearly impossible to lift that Sailun back in place. But no worries about it coming off.
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Old 06-07-2020, 10:02 AM   #57
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Although they are out of stock, I see Speedy Tire has the best price?!!

That is a great price, no doubt out of stock
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Old 06-07-2020, 01:05 PM   #58
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We got our 3791 just when that new RVIA rating changed and it came with the Sailun 637 ST235/80R16 rated at 4050#. My question has always been why are the rims rated at 3750#? When I replace, I want to go with higher rated rims (17.5") and the appropriate tire.
Why? your axles are 7000#. The wheels are far from being over loaded, even at maximum tire inflation of 110 PSI.

Your OE tires provide more than 1000# of load capacity reserves per axle.
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Old 06-07-2020, 02:25 PM   #59
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I think this is a good question. If the tires have to have a 10% reserve capacity, why not the rims they ride on? 3750 lbs doesn't provide a 10% reserve.
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Old 06-08-2020, 07:14 AM   #60
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I think this is a good question. If the tires have to have a 10% reserve capacity, why not the rims they ride on? 3750 lbs doesn't provide a 10% reserve.
The result of stresses on rubber is much different than the result of the same stresses on metal.

The guidance we get from the USTMA is; don't exceed a wheel's load capacity or PSI limit.

The 10% load capacity reserves for RV trailer tires is not a binding regulation, it's a recommendation from an organization (RVIA) that has a powerful influence on the RV trailer industry.
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