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Old 07-23-2015, 02:14 PM   #1
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Smile Tire Pressure

I'm sure this has been discussed a lot in the past but being a newbie I do have a pretty basic question regarding Motorhome Tire Pressures.
My tire size is 225R70x19.5
The Maximum cold PSI on the tire is listed as 95
The chart inside the coach beside the drivers seat says Maximum Front 65 and rear 60
Confused.
any suggestions?
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Old 07-23-2015, 02:23 PM   #2
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Tire mfgr. sets tire max at 95psi; never exceed that. RV mfgr. thinks it's rig is doesnt weigh too much and is safe on less than max tire pressure. You must weigh each axle and use the tire mfgrs. chart to determine the correct psi to use.
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Old 07-23-2015, 02:27 PM   #3
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If you inflate to the 95 as shown on the tire, and use the allowable load that that gives you (from the tire load table) you will be exceeding the max allowed load on the front (rear) axle installed on your coach. In other words, you will have more load carrying ability in the tires than the axles are rated to support. No problem if you inflate to the sidewall pressure other than a harsher ride, but no more load carrying ability. To give a more stable ride I might try 70-75psi to stiffen the sidewalls.
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Old 07-23-2015, 02:28 PM   #4
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Which brand of tires are on the rig? Go to the manufacturers website and find the load chart for your tires.
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Old 07-24-2015, 07:08 PM   #5
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I suggest you view this video. It is good at explaining many aspects of RV tire maintenance, including proper pressure.


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Old 07-25-2015, 11:15 AM   #6
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The chart (placard) inside the coach is the recommended psi value, not a "maximum" for the tires. It is, however, the pressure sufficient to support the maximum load the RV is designed to carry. If you have the same size tires as shown on the placard, you should be safe using that pressure. The psi shown on the tire sidewall says the tire can handle more, but it is not needed for your coach.

You can use the tire makers load-inflation table in conjunction with actual scaled weights if you want to optimize the tire pressure, or you can do what most do and simply go with the one-size-fits-all recommendation on the placard.
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Old 07-25-2015, 11:47 AM   #7
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Gary has the correct answer. You don't need to weigh your MH and set tire pressure per tire mfr chart to be safe, you are ok using the coach mfr recommended pressure as long as you don't exceed the carrying capacity on the coach mfr placard. To be extra safe you could air up to the max shown on the sidewall, but you will be paying the price with a more harsh ride.


And there are SO MANY questions regarding tires, I believe tires deserve their own sub-forum. Any one agree?
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Old 07-25-2015, 07:40 PM   #8
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You must confirm your installed tires are the same size listed on your coaches name plate.
Next get your rig weighed, front, rear, and each corner weight. Next get a load chart from your tire manufacturers web site to determine the optimum air pressure for your tires, AND add about five pounds pressure for a margin. BUT do not exceed the manufacturers maximum pressure stamped on the tire.
Make sure all tires on the same axle have the same inflation. If weights indicated left front is ok at 70 lbs pressure and right front indicates a pressure of 80 lbs is required, inflate BOTH to 80 lbs. Repeat same procedure on the rear axle.
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Old 07-25-2015, 09:49 PM   #9
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There is much misinformation about using load/inflation pressure charts. Michelin, Goodyear, Firestone, etc are members of the RMA=Rubber Manufacturers Association(ch4 addresses MH tires). Their websites say to never run less than the RV mfgrs, tire placard stated air pressure. ALL load/inflation charts display the MINIMUM pressure for the corresponding load, NOT the optimum.
A visit to Michelin,etc websites will confirm this.
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Old 07-25-2015, 11:28 PM   #10
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Quote:
Originally Posted by CJ7ole View Post
........And there are SO MANY questions regarding tires, I believe tires deserve their own sub-forum. Any one agree?

I'm not sure. My sense is that there are some new and different questions being asked about tires, but usually just the same questions asked over and over again.


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Old 07-26-2015, 09:44 AM   #11
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Thumbs down

You could say the same for batteries, and probably several other common components. Lots of questions, but highly repetitive. And even if you had a separate forum for them, folks would still post their questions in a brand specific forum, or general, or motorhome, or some other place. Trying to get people to post in the most suitable topic area is like herding cats...
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Old 07-26-2015, 04:39 PM   #12
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Quote:
Originally Posted by Canuck42 View Post
My tire size is 225R70x19.5
The Maximum cold PSI on the tire is listed as 95
The chart inside the coach beside the drivers seat says Maximum Front 65 and rear 60
Confused.
any suggestions?
It's a common fallacy: the tire sidewall does NOT list the maximum pressure. It lists the MINIMUM pressure required to carry the MAXIMUM LOAD!

The placard in the coach shows the pressure required to carry the RV, assuming the RV is loaded to its rated GVWR.

If you don't know how much your RV weighs, then the pressures that the RV manufacturers recommend is a safe number to use. If you weigh your RV and determine that you are significantly under the GVWR then you can safely adjust the pressures based on the tire manufacturer's load charts.
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Old 07-27-2015, 11:43 AM   #13
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Quote:
Originally Posted by Ray,IN View Post
There is much misinformation about using load/inflation pressure charts. Michelin, Goodyear, Firestone, etc are members of the RMA=Rubber Manufacturers Association(ch4 addresses MH tires). Their websites say to never run less than the RV mfgrs, tire placard stated air pressure. ALL load/inflation charts display the MINIMUM pressure for the corresponding load, NOT the optimum.
A visit to Michelin,etc websites will confirm this.

Ray - You're a seasoned RV vet and board member with just a few posts! I also salute and thank you for your service. I have no doubt that you feel you are providing important information with your comments above.

I however, agree with Gary's post. Actual ready to roll four corner weights and Tire Manufactures PSI charts, are and have been the way most threads I've read recommend. And I admit, it is what I recommend, with a few extra steps that I do that many may not. (If within the top 25% of the range, I move up to the next range of weights. I also add another 5 PSI to these recommended PSI's, to allow for extra weight added to the coach while traveling, and for long runs with strong steady side winds loading more weight onto the downwind side.).

Sure not trying to start an argument, but consider the practice of and advice of obtaining four corner weight, and setting PSI to the Tire Manufactures Recommended PSI settings, an important safety item. Sure, it helps in ride comfort too. But most important, having PSI I set to this value - provides the best handling for during emergency maneuvers situations. (I know 'emergency handling and maneuvers are not fun to think about in these large Class A's. But stuff happens, and every safety edge you can give yourself, could make a difference.)

And Ray, when I bought my 19" Goodyear G670's for my Bounder. And when I bought my current 22" Michelin XZE* tires for our Country Coach - I called and asked for Tech Support and both of the people I talked with said that getting four corner weight, and setting the PSI to their Charts PSI recommendation fro that weight - was the way to go. So, I feel I did proper due diligence.

If I'm wrong, and the hundreds of other posters here and on other boards that recommend this same practice - you are providing a valuable safety correction to us all. The trick, is figure out if we are 'actually wrong'!

Again, sure not trying to start any problems. But it is an important safety item, and clarification is important.

Best to you, and all,
Smitty
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