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  1. #11
    Rolling Along jim1521's Avatar
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    Pretty simple task.

    1. Weigh the trailer and establish how much weight is on the axles.
    2. Determine the max load rating for the tires that are on it and arrive at a % of max load. (i.e. trailer max load is 10,000 lbs. Trailer weighs 8,000 lbs on the scale. That's 80% of max load,
    3. Determine PSI for tires at full (100%) load. (i.e. 100 lbs PSI). Multiply 100 * .8 (this is 80% of max load), and that will give you your load rating. In this case Max tire pressure (cold) should be 80 PSI.
    2016 Grand Design Reflection 313RLTS
    2020 Riverstone 39FK
    2016 Ford F350 Super Duty 6.7L Powerstroke Lariat 2WD DRW

  2. #12
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    Quote Originally Posted by jim1521 View Post
    Pretty simple task.

    1. Weigh the trailer and establish how much weight is on the axles.
    2. Determine the max load rating for the tires that are on it and arrive at a % of max load. (i.e. trailer max load is 10,000 lbs. Trailer weighs 8,000 lbs on the scale. That's 80% of max load,
    3. Determine PSI for tires at full (100%) load. (i.e. 100 lbs PSI). Multiply 100 * .8 (this is 80% of max load), and that will give you your load rating. In this case Max tire pressure (cold) should be 80 PSI.
    Doesn’t work like that. The relationship isn’t linear. A 50% pressure reduction gives about a 35% load capacity reduction. When running tires below rated weight, contact the manufacturer to get a table of pressures.
    John & Kathy
    2014 F250 Lariat FX4 6.2L SBCC
    2014 Reflection 303RLS
    SW Indiana

  3. #13
    Rolling Along vonzoog's Avatar
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    ^^That would be correct.
    2018 Momentum 376TH
    2016 RAM 3500 Dually

  4. #14
    Commercial Member huntr70's Avatar
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    All you have to do is look at your own vehicles. Look inside the door and see what they recommend for pressures. Then compare to what is listed as max on the tire.

    Bet not many of them recommend the max....
    Steve- Inventory Manager at Tom Schaeffer's RV, Shoemakersville, PA www.tomschaeffers.com
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    2011 RAM 3500 SRW Outdoorsman Edition 4X4, 6.7 Cummins--TWEAKED!
    2021 Reflection 310RLS

  5. #15
    Long Hauler howson's Avatar
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    Quote Originally Posted by huntr70 View Post
    All you have to do is look at your own vehicles. Look inside the door and see what they recommend for pressures. Then compare to what is listed as max on the tire.

    Bet not many of them recommend the max....
    For vehicles you are correct. Often the pressures recommended for a car or truck are less than the maximum inflation pressure on the tires.

    But if we're going to assume the manufacturer's sticker recommendations are gospel, then the tires on a Grand Design should be inflated to that specification, too. For a 315RLTS, and I bet most campers, the recommended pressure on the sticker matches the Westlake's E-rated tire sidewall recommendation (80 psi).
    2017 Ford F-350 DRW 6.7L Platinum
    2019 315RLTS (purchased 16 Jul 18 from Campers Inn RV in Byron, GA)

  6. #16
    Site Sponsor Cate&Rob's Avatar
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    Quote Originally Posted by howson View Post
    For vehicles you are correct. Often the pressures recommended for a car or truck are less than the maximum inflation pressure on the tires.

    But if we're going to assume the manufacturer's sticker recommendations are gospel, then the tires on a Grand Design should be inflated to that specification, too. For a 315RLTS, and I bet most campers, the recommended pressure on the sticker matches the Westlake's E-rated tire sidewall recommendation (80 psi).
    GDRV (and other towable manufacturers) spec the minimum size tire that meets the requirements. This means that tire is inevitably spec’d at it’s maximum pressure. If you are upgrading to a tire of higher capacity than OE, I think it would be wise to consult the tire manufacturer’s load/pressure tables. They do have these tables for ST tires. Running a tire above it’s required pressure means a convex tread contact with the road and a rough ride for the trailer.

    Rob
    Cate & Rob
    2015 Reflection 303RLS

  7. #17
    Gone Traveling
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    I sense this argument will NEVER end. I guess I'm the clueless one, because I just go with what the engineers who designed the coach and tires recommend. I figure that they are probably better qualified to specify what grade tire and what inflation pressures should be run than the average schmo. So, moving forward, I'm just saving my breath and my patience and staying away form these circular tire posts. I'll stick with the engineers rather than the guys on the forum and just stop commenting on this nonsense. If the factory engineers say I should run G rated tires on my coach, that's what I'll run because ... well because they designed the damn thing. At the end of the day, how do you argue with the people who designed and built your coach? Unless you have an engineering degree and have several years of experience building coaches or designing tires, why on earth should anyone listen to you?

    By the way, I have NEVER gone wrong following the manufacturers recommendations. I also run max cold pressure and my stuff does not get destroyed due to rough ride, my springs don't bend, my tires wear beautifully and I've never had a tire self destruct (like Westlakes).

    I hope that you all have safe travels. Meanwhile, I'll be cruising around the country on my Sailuns, inflated to 110 PSI and with my factory suspension. Now, I'll be getting on some really important threads, like what's the best truck or what's the best oil (answers: Ford and Rotella).

  8. #18
    Seasoned Camper
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    Thanks for all the input. Got er home and inflated the tires to 110. In my province there is only 3 GD dealers. 2 hours, 4hours and 8 hours drive. The 2 hour drive dealer gave me the best deal, there only downside is they only suggest or even speak kindly about products thy install, any other product is deemed inferior. The tried selling me Michelin’s and when I showed up with sailuns they turn their nose at them. No biggie, it’s home and we stayed in it last time for the first Time, woke up to 20 deer feeding out of my moms bird seed pile in the back yard.


    Sent from my iPhone using Tapatalk
    2021 GMC 3500HD
    2021 Montana High Country 385BR
    2018 GMC 2500 HD (Traded in)
    2019 GD312BHTS (written off by fallen tree RIP)

  9. #19
    Long Hauler howson's Avatar
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    Quote Originally Posted by Chad1383 View Post
    Thanks for all the input. Got er home and inflated the tires to 110. In my province there is only 3 GD dealers. 2 hours, 4hours and 8 hours drive. The 2 hour drive dealer gave me the best deal, there only downside is they only suggest or even speak kindly about products thy install, any other product is deemed inferior. The tried selling me Michelin’s and when I showed up with sailuns they turn their nose at them. No biggie, it’s home and we stayed in it last time for the first Time, woke up to 20 deer feeding out of my moms bird seed pile in the back yard.


    Sent from my iPhone using Tapatalk
    Please see @Rob's note in post #16. Since you are using G rated tires on a trailer spec'd for E's, I urge you to call Sailun and ask them what pressure they recommend for your 10,995 GVWR trailer.

    Because I feel like I may have led you astray based on my initial recommendation to "inflate to max", I went searching and found a Sailun Load Chart on the Heartland Forum (https://heartlandowners.org/showthre...nflation+Table). I registered and was able to download the table (see attached PDF).

    Click image for larger version. 

Name:	Sailun Load and Inflation 23580 23585 ST.pdf 
Views:	20 
Size:	23.4 KB 
ID:	16583

    I'm not 100% sure what "Single" vs "Dual" means in the chart, so understand that I am assuming the terms are the same as they are used when referencing a truck. In the case of our RVs, I think the "Single" line is appropriate (meaning a single tire on one side of an axle, versus two on a dually truck or commercial trailer). If I'm wrong someone will chime in.

    To match the Westlake E rating of 3,520 per tire it looks like 85 PSI is the correct pressure for the Sailun ST235/80R16. Again, please verify this with Sailun. My purpose in attaching the chart and speculating on the potential pressure difference from 110PSI is to motivate you to follow up with the tire manufacturer.

    Please let me (and the rest following this thread) know the final pressure you decide to run and why.

    -Howard
    2017 Ford F-350 DRW 6.7L Platinum
    2019 315RLTS (purchased 16 Jul 18 from Campers Inn RV in Byron, GA)

  10. #20
    Commercial Member huntr70's Avatar
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    Quote Originally Posted by BigGuy82 View Post
    I sense this argument will NEVER end. I guess I'm the clueless one, because I just go with what the engineers who designed the coach and tires recommend. I figure that they are probably better qualified to specify what grade tire and what inflation pressures should be run than the average schmo. So, moving forward, I'm just saving my breath and my patience and staying away form these circular tire posts. I'll stick with the engineers rather than the guys on the forum and just stop commenting on this nonsense. If the factory engineers say I should run G rated tires on my coach, that's what I'll run because ... well because they designed the damn thing. At the end of the day, how do you argue with the people who designed and built your coach? Unless you have an engineering degree and have several years of experience building coaches or designing tires, why on earth should anyone listen to you?

    By the way, I have NEVER gone wrong following the manufacturers recommendations. I also run max cold pressure and my stuff does not get destroyed due to rough ride, my springs don't bend, my tires wear beautifully and I've never had a tire self destruct (like Westlakes).

    I hope that you all have safe travels. Meanwhile, I'll be cruising around the country on my Sailuns, inflated to 110 PSI and with my factory suspension. Now, I'll be getting on some really important threads, like what's the best truck or what's the best oil (answers: Ford and Rotella).
    Well, for one thing, there is no argument.

    Secondly, the engineers designed your coach with E range tires. GD then added the option to install Goodyear G614 tires. Since most dealers ordered the bigger coaches with the G's, they then went standard on Solitude and Momentum.

    Since we are talking about a Reflection travel trailer, I still feel G range tires (no matter what brand) are overkill for the GVWR, especially at max pressure. Hopefully, they won't be over stiff and beat his trailer apart....
    Steve- Inventory Manager at Tom Schaeffer's RV, Shoemakersville, PA www.tomschaeffers.com
    [email protected]
    2011 RAM 3500 SRW Outdoorsman Edition 4X4, 6.7 Cummins--TWEAKED!
    2021 Reflection 310RLS

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