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Old 02-27-2016, 12:25 PM   #21
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I looked at the Michelin RV tire chart for your size tire with the H rating and the front tires based on the weight you provided should be between 105 and 110 Psi. Are you sure about the weights you provided for the drive axle and the tag? The drive seems light and not even listed for dual wheel and the chart starts at 9080 lbs. at 75 Psi. When you take the 15020 and divide by 2 you get 7510 pounds for each side of the axle which is below the listed minimum for dual wheels. The same is true for the tag tires.
I would have the coach reweighed with 6 point weight readings before going further trying to figure out your proper tire pressure.
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Old 02-27-2016, 12:31 PM   #22
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Marty I noticed the same when I looked at my chart and assumed (bad idea) that a person would go with the minimum pressure rating listed.
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Old 02-27-2016, 12:42 PM   #23
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Life is way too short to worry with these things, folks. Take a look at your tires. What does it indicate is the max pressure cold? Mine say 120 psi. Put that much air in all your tires and be done with it. It's an RV for pity sake, not a Rolls Royce. The ride may not be as smooth as you like, but you won't be blowing tires!
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Old 02-27-2016, 12:58 PM   #24
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"The vehicle manufacturer (not the tire manufacturer) has developed these numbers based on the axle distribution, gross weight and other oddball factors the tire maker could not foresee in a specialty application."

And assumes you are running the OEM tires. I use a tire only for the service for which the tire was manufactured, and inflate as per the tire manufacturer's guidance. The only time I consider the RV label as gospel is when it still has the original equipment tire - since this assumes the RV manufacturer has made the correct choice per tire manufacturer's specs)

Just imagine the liability issues the OEM would face if a serious accident due to tire failure occurred, and a sharp investigator determined the OEM label did not reflect the tire manufacturer's specification.

When I bought my dually, it had street-tread tires on it. These were replaced with BFG AT/KO tires. I know the inflation pressures on the door sticker are not correct for the BFGs. The BFGs would be significantly underinflated. (I have experienced this personally - having run BFGs on my trucks for over 40 years and experienced the rapid wear if I inflate to sticker pressure.)
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Old 02-27-2016, 12:58 PM   #25
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Life is way too short to worry with these things, folks. Take a look at your tires. What does it indicate is the max pressure cold? Mine say 120 psi. Put that much air in all your tires and be done with it. It's an RV for pity sake, not a Rolls Royce. The ride may not be as smooth as you like, but you won't be blowing tires!

I really didn't want to comment but I can't stop. This is just not a good idea. It isn't hard to figure out the weight. In this case no one here is familiar with tag axle and psi. In any case it is well worth taking the time to set the psi correctly on you tires. Tires are very expensive and who wants to replace them before you need to? Also my life and my family's life is worth taking a few minutes to get it right. I know that most have never weighted their Moho. That's up to them but it is just not a good idea to run it up to max pressure and go.
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Old 02-27-2016, 01:04 PM   #26
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"The vehicle manufacturer (not the tire manufacturer) has developed these numbers based on the axle distribution, gross weight and other oddball factors the tire maker could not foresee in a specialty application."

And assumes you are running the OEM tires. I use a tire only for the service for which the tire was manufactured, and inflate as per the tire manufacturer's guidance. The only time I consider the RV label as gospel is when it still has the original equipment tire - since this assumes the RV manufacturer has made the correct choice per tire manufacturer's specs)

Just imagine the liability issues the OEM would face if a serious accident due to tire failure occurred, and a sharp investigator determined the OEM label did not reflect the tire manufacturer's specification.

When I bought my dually, it had street-tread tires on it. These were replaced with BFG AT/KO tires. I know the inflation pressures on the door sticker are not correct for the BFGs. The BFGs would be significantly underinflated. (I have experienced this personally - having run BFGs on my trucks for over 40 years and experienced the rapid wear if I inflate to sticker pressure.)

Remember that a Moho is built on a chassis. You have two manufacturers at work here. FR will give psi for max weight. fL also will give psi for max chassis weight. Neither of these manufacturers know what your Moho weighs so how would they know where to set the psi. Each owner must get a 4 point weight and adjust their tires to that weight. This is a Moho not a truck. Not a pick up and not a over the road tractor. They are different and need to be handled as such.
Sorry to the OP for all the side track.
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Old 02-27-2016, 01:26 PM   #27
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Tire pressure

The higher the psi the cooler it runs. The cooler tire is a much more reliable tire,and that means a safer tire. But not above maximum pressure. And you don't need to change according to climate. That is built into specs that are listed on your tire. Or on your coach.
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Old 02-27-2016, 01:32 PM   #28
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Twice, after doing some research on other Motohome forums here the best I gathered.

I couldn't quote or copy paste the link but it is basically said if your weights are less than what is listed on the tire charts then you should run your air pressure at 75% of the Max pressure listed on the side wall of the tire. So if you max is like mine at 120psi you should run no less than 90psi on any given tire.


Also, you have a FL chassis, a non adjustable pressure regulator is installed for the tag axle. If you want to you can drill out a pop rivet on the regulator that locks the ability to adjust the pressure of the air bags on the tag axle. This gives you the ability to use less pressure on the tag axle air bags which in turn will add more weight to the drive axle and takes some weight off the steer axle.

Adding pressure to the air bags on the tag will have the opposite effect.

I hope this info helps you.
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Old 02-27-2016, 01:34 PM   #29
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Ron
I looked at the Michelin RV tire chart for your size tire with the H rating and the front tires based on the weight you provided should be between 105 and 110 Psi. Are you sure about the weights you provided for the drive axle and the tag? The drive seems light and not even listed for dual wheel and the chart starts at 9080 lbs. at 75 Psi. When you take the 15020 and divide by 2 you get 7510 pounds for each side of the axle which is below the listed minimum for dual wheels. The same is true for the tag tires.
I would have the coach reweighed with 6 point weight readings before going further trying to figure out your proper tire pressure.
Marty


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Marty, the weights are correct. Had them weighed on two different cat scales. My weights on drive are approximately 1200# heavier than empty weights from factory. This equates to full water and clothes, etc. Remember gvw for coach is 43000# and we are now only at 35200# shipped weight was 32495#.
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Old 02-27-2016, 01:48 PM   #30
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Originally Posted by Campin Cajun View Post
Twice, after doing some research on other Motohome forums here the best I gathered.

I couldn't quote or copy paste the link but it is basically said if your weights are less than what is listed on the tire charts then you should run your air pressure at 75% of the Max pressure listed on the side wall of the tire. So if you max is like mine at 120psi you should run no less than 90psi on any given tire.


Also, you have a FL chassis, a non adjustable pressure regulator is installed for the tag axle. If you want to you can drill out a pop rivet on the regulator that locks the ability to adjust the pressure of the air bags on the tag axle. This gives you the ability to use less pressure on the tag axle air bags which in turn will add more weight to the drive axle and takes some weight off the steer axle.

Adding pressure to the air bags on the tag will have the opposite effect.

I hope this info helps you.
CC: I had 85# floating around in my head. But, just for argument's sake, if 75% of 120 is the minimum, why does Michelin have 75psi in the chart?

I don't believe I want to start messing with suspension pressure in tag, because the stability on the road is phenomenal. Seventy mph in 20-35 mph winds and steady as a rock.

Thanks for the input.
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