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 > Tire Load/Inflation Calculation

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rfloyd99

Colorado & Florida

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Posted: 03/28/22 03:28pm Link  |  Print  |  Notify Moderator

Exactly three years ago I bought new tires for my Jayco 23' (27'OAL). I had previously had the trailer professionally weighed at an Escapee's weigh station where they weigh the load on each tire. Unfortunately, that information is in Colorado, and I'm in Florida. But I remember that the total weight was 5500 lbs. We were fully loaded for a three month trip, and that is within the GVWR of 5995 lbs.

The tires (Goodyear Endurance ST205/75R14) are rated for for a load of 2040 lbs (per tire). I knew I didn't have that much wt, so I ran them at 55 psi, thinking I would do some research when I had more time to figure out recommended psi.

Well, three years and many thousand miles later, I finally looked it up. The chart on Goodyear's site shows a psi of 40 for a load of 1500 lbs. 25% of 5500 is 1375, which calls for a psi of 30-35. I increased the wt estimate by 10%, since there may be more weight on an individual tire. That's where I got the 40 psi estimate.

A psi of 35-40 just seems low to me. We are about to leave on a trip of 2,500 miles, and I would like to get this right.

Anyone have expertise in this?

Thanks!

enblethen

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Posted: 03/28/22 04:10pm Link  |  Print  |  Notify Moderator

I would suggest weighing the rig first. You maybe surprised. I don't trust weights provided by manufacturers.
I didn't see any numbers for the tongue weight.
From your numbers, I would be inflating closer to 50 PSI.
Inflation chart


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JimK-NY

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Posted: 03/28/22 04:31pm Link  |  Print  |  Notify Moderator

They are designed for a maximum load of 2040# @ 65 psi. That is where I would run them. I have heard of and seen lots of tire failures due to underinflation. At worse running at higher than necessary pressures will give you a bit of excessive tire wear but with a much lower risk of a failure. Odds are you will replace the tires due to age way before wearing them out.

time2roll

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Posted: 03/28/22 04:36pm Link  |  Print  |  Notify Moderator

+1 for 65 psi unless they seem bouncy when driven. Better fuel economy too. No reason to aim for the minimum here.


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theoldwizard1

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Posted: 03/28/22 05:33pm Link  |  Print  |  Notify Moderator

I have always heard that on trailers, set the cold tire pressure to the maximum specified on the sidewall.

wildtoad

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Posted: 03/28/22 05:42pm Link  |  Print  |  Notify Moderator

People in motorhomes seem to obsess about tire pressures, mainly because the don’t want to under inflate(Bad) nor do they want a harsh ride by using the sidewall pressures unless their actual weights require it, or cause unusual tire wear.

As above I’ve always heard for boats trailers, travel trailers, etc to use the pressure on the tire. Ride comfort not so important. But this may be old anecdotal information.


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Cummins12V98

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Posted: 03/28/22 06:43pm Link  |  Print  |  Notify Moderator

Measure the tread depth across the tire. How is it wearing?


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bob213

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Posted: 03/28/22 07:33pm Link  |  Print  |  Notify Moderator

Why would Goodyear print a table for PSI if lowering the PSI damages your tires? If you inflate them according the the weight they are carrying I see no problem running less than the sidewall max of 65 lbs.


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JimK-NY

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Posted: 03/28/22 08:45pm Link  |  Print  |  Notify Moderator

bob213 wrote:

Why would Goodyear print a table for PSI if lowering the PSI damages your tires?


Note, the table is for maximum load ratings at various pressures. Most of us have had or seen tire failures and want to run at less than the maximum allowed load.

bob213

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Posted: 03/28/22 09:01pm Link  |  Print  |  Notify Moderator

My trailer came with LR "C" tires. If I'm running my LR "E" tires at 58 lbs psi (7lbs. below max) I still have a load capacity of 7500 lbs which is 480 lbs. more capacity than the "C" at max load. I see no need or problem with running with 7 lbs. less than max and get a much less bouncy ride. If there's info to support running only at max psi, the tire mfgs. must not be looking at it.

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