2003 Alpine 36MDDS weight

[Kid Gloves]

Originally Posted by Astasoftride

From owning an F350, I thought the duel tire pressure was more due to potential tire interactions. Meaning with lower pressures (for the same weight) the tire would bulge out a bit more. This then could lead to the two tires rubbing which would be a bad thing or at least the space between the two being greatly reduced.

I think I wrote the wrong number earlier. For the Toyo 295R80/22.5 @ 9880 it is 80 psi.

You are correct. I looked up a chart for your tires and it showed 80 front and 80 rear for your posted weights. At maximum axle ratings it would be 105 front and 90 rear. In my opinion, at your current weight, you’d be properly inflated at 90-95 all around.

[Old Scout]

My early 2003 model has a 12k front and a 19k rear axle--WRV went to an upgraded 13k front and 20k rear axle some time during the 2003 model year. Looking at the Toyo tire pressure charts, I like the 100 lbs for the fronts as that would fully cover your max front axle weight; similarly, 90 for the rear would cover your max there. Suppose you could go with a bit less pressures but what would be the point?

[Jeep401]

As a side note, a little extra pressure in the fronts will take a little stress off the steering box bracket.
It's not like most of us will ever actually wear out a set of tires.
I would also add that you don't want to go way over the chart recommendations because you could start to affect the contact patch of the tire.

[Kid Gloves]

Originally Posted by Jeep401

As a side note, a little extra pressure in the fronts will take a little stress off the steering box bracket.
It's not like most of us will ever actually wear out a set of tires.
I would also add that you don't want to go way over the chart recommendations because you could start to affect the contact patch of the tire.

Agreed. More is better, until it’s not.

If the chart says 80 and you inflate to 100, the tires are 25% above the recommended minimum pressure for the given weight. Actual tire experts recommend adding 10-20% to the recommended chart pressure. We aren’t likely to see premature wear from overinflated tires if we only drive 5-10K miles a year. The ride might be a bit more harsh, handling may be compromised, stopping distances may increase. It’s a choice.

If you add 3,000lbs to the coach, revisit the charts.

[Old Scout]

Based on my previous comments: underinflated, just right, or overinflated....I'll go with a little over-inflation every time--just saying....safe travels!

[Kid Gloves]

Originally Posted by Old Scout

Based on my previous comments: underinflated, just right, or overinflated....I'll go with a little over-inflation every time--just saying....safe travels!

Let’s define those categories.

1) Under-inflated: Any pressure below the recommended chart pressure.
2) Just Right: Any pressure above the recommended chart pressure that does not exceed chart pressure plus 20%. Preferably between 10-20% above the recommended chart pressure.
3) Overinflated: Any pressure that exceeds chart pressure by 20% or more.

The 10-20% recommendation offers us a Just Right range of 10%. Ten percent of 80 is 8, 10% of 100 is 10. For many of us, we therefore have an 8-10 psi range within which to keep our tires properly inflated. This should not be a difficult challenge. Accomplishing this should not occupy a great deal of our time.

Keep in mind that we round up in 5psi increments on the chart as well. So, we could be as much as 4psi over just by rounding up. That is, if we were to build a chart in 1lb increments. That’s 4-5%, then add another 25%, from say 80 to 100. Now we’re pushing 30%.

It’s just too easy to keep it between 10-20%. So why knowingly go just a little over? Makes no sense.

[Astasoftride]

Originally Posted by Kid Gloves

You are correct. I looked up a chart for your tires and it showed 80 front and 80 rear for your posted weights. At maximum axle ratings it would be 105 front and 90 rear. In my opinion, at your current weight, you’d be properly inflated at 90-95 all around.

Just to muddy the water just a little bit (hopefully not too much).

The sticker at the front shows GVWR psi numbers of front 110 and rear 95.

[Kid Gloves]

Here’s a screenshot of the chart that I referenced.

(On edit)
Well, that’s pretty much unreadable. There are 2 separate 295/75 R22.5’s listed with different load and psi recommendations. Guess you have to search for it in your own.

[Astasoftride]

Yes. That looks like the same one that I found. The two lines, the first is for load range G and the second is for load range H. My tires are load range G

[Kid Gloves]

Indeed, I was just looking at the chart again and noticed that the discrepancy was due to the different load ratings. Another reason it is important to inflate your tires based on the weight of your coach. Glad you have it sorted out.