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Old 08-04-2021, 11:31 AM   #1
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Cold tire load/inflation

I have a 2018, 33 ft Keystone Springdale Travel Trailer with 2 axles. Model SG287RB.

I know there are alot of articles on this sublect both here on IRV2 and on-line. Believe me I have spent numerous hours on this subject. Several years ago I researched this subject and came to the conclusion that (short of getting the RV weighed) i should set my cold tire pressure to the maximum PSI on the tire, which was 65psi. The cold tire inflation on the plate on my door jam from the factory also stated 65psi so I felt safe.

I recently replaced my tires with Goodyear Endurance tires (ST225/75R15) and acquired the load/inflation information from Goodyear for these tires. I also got my trailer weighed at a Loves weigh scale. The total weight of the 2 axles (which are right next to each other) was 8200lbs. I divided this weight by 4 which came to 2,050lbs per tire. The closest weight on the Goodyear inflation chart was 2150 which recommended 50PSI. The RV specification Plate states 65psi for a different tire. My new tires have a maximum pressure of 80PSI. Which PSI should I go with. IM thinking 65PSI as its greater then the Goodyear chart but less then the tire max PSI and matches the RV plate.

I know its best to have each tire weighed individually but i dont have the means of doing that at this time. Please provided your thoughts on this.
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Old 08-04-2021, 12:10 PM   #2
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Are the GY Endurance same size as OEM tires???
*OEM ST225/75R15 also??

8200# was total axle weight....equally divided each tire would be 2050#
BUT weight is NOT equally distributed across each tire/each axle
One axle could carry more weight
One side of trailer could be heavier

Run 65 psi then check thread wear
Sidewalk chalk...big stick
Make a wide mark across each tire thread
Drive straight forward for 25'...Straight/no turning
Then check chalk mark
Even wear ....good PSI
Chalk worn off at edges.....to low PSI
Chalk worn off center.........to hi psi
Adjust accordingly
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Old 08-04-2021, 12:14 PM   #3
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I would use 65 - 70 PSI. My ORV 21RBS weighs about the same and came with the LR E Goodyear Endurance tires in that size. Trailer sticker says 80, tire sidewall says max 80, load chart from Goodyear says I only need 45psi minimum for the load. I run 70 and plan on checking the contact patch.

As you know, some will say to go by the tire sidewall, some will insist you go by the sticker on the trailer and some will say to use the inflation chart and weigh it.
In my opinion, the tire stamp is the max pressure; the sticker isn't likely derived from any real engineering and the tire pressure chart shows the MINIMUM pressure for the load so in your (and my) case you have a minimum of 50 and a maximum of 80 and since a bit more pressure is better than too little, I error on the side of caution and go closer to the Maximum. It's hard to argue that you need 80psi when your trailer came equipped with 65psi tires originally.


2 cents,



2 cents,
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Old 08-04-2021, 12:24 PM   #4
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Tire pressure ratings listed in the load chart are the MIMIMUM not maximum to carry the referenced load.

You can safely run 50 psi for the 2150 rating, or even higher. In reality you likely will not have the load evenly spread amongst all 4 tires, some will carry a larger portion of the load.

Under inflation leads to overheated tires and blowouts, "over inflation" has little down side, tires run cooler and you are less likely to have a blow out. The only real negative is if you run a lot higher than your load requires you may wear the tread in the center of the tire faster than the edges, which usually isn't a problem on a tandem axle trailer since tires get scrubbed a lot while turning.

Highly suggest reading the blog posts at the website below. The guy that runs it is a retired tire design engineer. I learned a lot.

https://www.rvtiresafety.net/
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Old 08-04-2021, 01:54 PM   #5
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Having owned several motor homes prior to our current trailer you learn there is a downside with too much pressure…..why beat your trailer up more than necessary.

Original tires on our trailer were 50 psi max, now running with Endurance that can be ran up to 65psi.

Kept them at 50 psi, and so far the running pressure, and temps are looking good. Lower temps than the original. Goodyear load chart says I can go lower, but like where they are at with extra capacity.

Would never go without a TPMS.
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Old 08-04-2021, 02:04 PM   #6
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Quote:
Originally Posted by bneukam View Post
Having owned several motor homes prior to our current trailer you learn there is a downside with too much pressure…..why beat your trailer up more than necessary.

Original tires on our trailer were 50 psi max, now running with Endurance that can be ran up to 65psi.
When I went up a load rating and increased from 50 to 65 psi... I really didn't notice much differnce in the bounce. Got tired of getting blow outs when traveling the hot regions of the southern US... haven't had any since. (I'm below GVWR so not overloaded, but GVWR was at the limit of the OEM tire ratings)

The best thing I ever did to reduce bounce was to replace my equalizers with Lippert Road Armors. I did this after upgrading to a heavier tire so I did have a fair comparison of 50 vs 65 psi.

I highly recommend upgrading equalizers to something like the Road Armors.
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Old 08-04-2021, 02:17 PM   #7
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Quote:
Originally Posted by jrollf View Post
When I went up a load rating and increased from 50 to 65 psi... I really didn't notice much differnce in the bounce. Got tired of getting blow outs when traveling the hot regions of the southern US... haven't had any since. (I'm below GVWR so not overloaded, but GVWR was at the limit of the OEM tire ratings)

The best thing I ever did to reduce bounce was to replace my equalizers with Lippert Road Armors. I did this after upgrading to a heavier tire so I did have a fair comparison of 50 vs 65 psi.

I highly recommend upgrading equalizers to something like the Road Armors.

Not talking about bounce, but the harsh impact when the rubber meets a pothole.
You won’t notice this unless your riding in the trailer.
Have torsion axels on our current trailer. Trailer rides very smooth.
Understand we all have different thoughts on this, but for me I will follow Goodyear’s chart within reason, and watch my TPMS.
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Old 08-05-2021, 02:47 AM   #8
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Tire pressure sweet spot

What OldBiscut said, find the sweet spot for your rig and not what someone thinks it should be, use the published tire manufacturer inflation to weight tables and add about 10% to make up for the weight that may not be exactly even on your rig..
Other references:

https://tirepressure.com/


https://youtu.be/_eW2MfspLSQ All About RV’s Jared Gillis

If inflated to maximum psi. and it’s not required, 🙂 the tire will run to heavy in the center placing undue stress on the overall casing construction and wearing out the center tread prematurely. If under inflated 🙁, the tire will wear heavy on the outside tread and sidewall causing stress on the construction of the tire and possibly a delamination event.
Your target psi. is a nice even tread face 😐 contact to the ground. Use the min. max. information which the manufacturer has supplied you with and trust what the tire is showing you.

Make 2-5 PSI adjustments up or down until you visually observe that nice even tread to ground contact.

Its good to see others not in the “I run my tires at maximum cold PSI” camp. In resent temperatures max cold inflation out of the driveway will cause other issues in the suspension systems. Pressure = heat.
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Old 08-09-2021, 05:54 PM   #9
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ST tires undergo extreme sidewall stress with tandem axles. That is why some ST tire mfgrs. say to use the sidewall listed inflation pressures. Carlisle Tire warranty used to state if sidewall listed pressure is not used the warranty is void.
FWIW several years ago one summer in E. TX I watched a man make a spot turn on a wide city street, the sidewall stress was so bad on that blacktop street he rolled a tire enough to break the bead, causing the tire to go flat immediately.
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