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Old 11-14-2018, 08:21 AM   #1
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Tire pressure vs. load?

So I posted earlier about rough roads tearing my RV apart. Someone replied that I should reduce the PSI of the tires to match the load in order to soften the ride. So I am trying to research that idea. I found the chart below for Michelin but having some trouble understanding it. Assuming I have my RV weighed and know the weights on each axle, can I set the pressure to match the weight based on a chart like this for the tires I have? Do you do this or do you just run it to the max PSI listed, which is what I do. 75 psi up front, 80 psi in the rear.


Michelin Load & Inflation Chart
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Old 11-14-2018, 08:51 AM   #2
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I am a big fan of using the load inflation charts instead of max.

Unless you find and pay for individual wheel weights you will get one number for all the trailer axles. Take this number divided by the number of tires. Since all the tires will never have the same weight add about 25% to this number and set the inflation based on this number.

Be sure and do the weights with the camper ready to go and if you get individual weights use the highest and don't add the 25%.

Edit: Missed the motor home part so yes be sure to do the axles separately, grain type scales generally do the entire vehicle at once, truck stops / CAT scales will have 3 separate platforms. Still apply the 25%
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Old 11-14-2018, 10:12 PM   #3
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Yes, there's no reason to use max psi if the axle is not maxed out. Remember, however, to use the same psi (from the load table) on both tires on the same axle. In other words, if you have 2,500lbs on the left tire and 3,000lbs on the right tire on a 7000lb axle, both tires are aired for 3,000lbs.
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Old 11-14-2018, 10:40 PM   #4
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Look into putting shocks on the trailer ??????


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Old 11-15-2018, 08:29 AM   #5
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Quote:
Originally Posted by Oaklevel View Post
Look into putting shocks on the trailer ??????


SQUIRREL!!!!!!!!! what does putting shocks on a trialer have to do with the tire pressure/load on a rv?

thx.

I just keep them at the 75/80 pressure. I wouldnt want premature tire wear from underinflation.

Bob
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Old 11-15-2018, 10:22 AM   #6
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65-70 psi here on my 2251 (about 11k loaded).
I never go to max with my small rig.
No unusual tire wear. I will replace them anyway in 5-6 years long before the tread wears out.
Mine rides pretty good...especially with the motorcycle on the rear.
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Old 11-15-2018, 10:40 AM   #7
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I had the same issue when I went from stock tires to Goodyear Endurance. I had them put on and had max PSI 85PSI in the tires. Stuff started to come apart within the camper. After advice from people on this group I reduced the PSI per the Goodyear tables for my weight and now run 65PSI. All is well now.

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Old 11-15-2018, 01:51 PM   #8
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Originally Posted by Shredder View Post
I just keep them at the 75/80 pressure. I wouldnt want premature tire wear from underinflation.
X2...I have never been concerned about load and not have had any issues with 33,000 miles at those PSI having had 2 sets of Michelin since day one.
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Old 11-15-2018, 01:57 PM   #9
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How so you like the Endurance tires. Does the 2703WS sway less. Did you replace valve stems with something else?
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Old 11-15-2018, 02:44 PM   #10
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I believe that your Michelin chart is the wrong one. You need the tire pressure vs load chart found here:

https://www.michelintruck.com/refere...tion-tables/#/

After you weigh your rig, then you can use the tables to determine the PSI of the tires. Note that there are different values for single tires vs dual tires. Also, at most places, you can get separate weights for the front vs rear axles.
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Old 11-15-2018, 02:47 PM   #11
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Just remember....

Those pressures are the MINIMUM for a given load.

NOT the 'correct' pressure for a load.
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Old 11-15-2018, 03:21 PM   #12
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I've wondered about this for a while, and have been blindly following the original advice of my dealer to use 45psi. (Note ours is a dual-axle TT and weighs out about 5000 lbs loaded.)

Doing a Google search for trailer tire load inflation tables there are a bunch of tables for a couple brands and lots of good info.
Here are some of the tables (there are similar for larger truck tires):
https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
https://www.maxxis.com/trailer/trail...nflation-chart
https://www.michelinrvtires.com/refe...tion-tables/#/
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Old 11-16-2018, 09:53 AM   #13
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I have a single axle Rockwood minilite. I just put on Edurance 215/75R14 tires. The trailer weighs 3500 lbs when fully loaded. What do I set the air pressure to in both tires? The chart shows a max of 2200 lbs. Do I take my weight and divide by 2 and use that load for tire pressure? It doesn't sound right.
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Old 11-16-2018, 12:36 PM   #14
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rbarmhome: If you are looking at the tire/load chart for your tire manufacturer, the charts usually gives 2 values for a tire; one when used as a single tire and the other when used as a dually tire. If your chart says 2200 lbs per tire and the chart is for a single tire, then you can carry a total of 4400 lbs, 2200 for each tire - assuming you have a tire on each side of your TT.

Remember that the charts represent the minimum tire pressure for the load, as others have said. I always carry 5 PSI higher than the charts for safety reasons.

Another reminder. The charts are for COLD tires. As you drive, the tire pressures will naturally rise.
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Old 11-16-2018, 01:59 PM   #15
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Well, getting mixed signals here. But that is ok. I believe next season I will consult the table, add some for a safety margin, and air down a bit and see how it rides.

Thanks everyone.
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Old 11-16-2018, 02:16 PM   #16
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Well, getting mixed signals here. But that is ok. I believe next season I will consult the table, add some for a safety margin, and air down a bit and see how it rides.

Thanks everyone.
Yep, you're getting mixed signals because many people have many opinions. But your statement here is dead on.

Use the table, but be sure to add some for margin of error. And I'm glad others have pointed out that those are minimum pressures for a load. Many folks on this forum will quickly shout out with anecdotal stories of how they've done it for 20 years, and it's always been fine for them. Anecdotes are fine... but go with researched 'best practices.'
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Old 11-16-2018, 02:18 PM   #17
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I'd bet this thread goes up to 20 pages in one day...
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Old 11-16-2018, 02:34 PM   #18
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One final and parting shot on this subject. You have a Sunseeker and for those people posting, the Sunseeker is a Class C with a single tire on the front axle and a set of duallies in the rear. While getting your rig weighed at all 4 corners is ideal, it's hard to find a place that can do that. The alternative is to get your weight per axle, I have found that at many scales, you can drive up and only put the front axle on the scale. Get the weight then drive the entire RV onto the scale and get the total weight of your coach. The total weight minus the front axle weight gives you the weight on the rear axle.
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Old 11-17-2018, 12:14 PM   #19
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You are getting mixed signals because most of the responses are from folks who don’t know that Class C MH tires are HD Light Truck tires that are vastly different than trailer tires. It’s up to you to decide what is good info and what is rubbish.
You have a placard that gives you proper inflation pressures for GVWR. I believe that when you weigh your unit (loaded) you will find that the load table pressures plus safety percentages will equal what the RV manufacturer with input from the tire manufacturer recommended in the first place.
Safe travels
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Old 11-17-2018, 04:14 PM   #20
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You are getting mixed signals because most of the responses are from folks who donít know that Class C MH tires are HD Light Truck tires that are vastly different than trailer tires. Itís up to you to decide what is good info and what is rubbish.Safe travels
I agree. Info I've gotten from tire engineers and related experts:

For TOWABLES - always fill tires to max pressure specified on the tire. End of discussion. Towables are most susceptible to problems from tread separation and overheating especially on multi-axle trailers. Fully inflating the tire alleviates these issues.

For DRIVEABLES - inflate to pressure in manufacturers guide based on actual weights by wheel. Determine weights per wheel and use the highest wheel weight per axle for the appropriate inflation pressure for tires on that axle. Guide will specify different inflation for single vs dual tire setups.

For the following, I'm not entirely sure this covers ALL tires. I know it is true for most. The weight / air pressure specification is a standard developed by one of the three major tire standards organizations ETRO (Europe), TRA (US), or JATMA (Japan). If you can't find a table from your manufacturer, check the standards groups for info. The three groups specifications are generally identical or only marginally different.
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