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Old 11-27-2018, 10:24 AM   #1
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Tire inflation pressure

After driving my 2017 Coachmen Prism about 10K miles I noticed that the outside shoulders of the front tires were wearing down rather quickly. When I dropped the unit off at a local Mercedes dealer for its annual maintenance I asked about the wear. The service manager told me that it was caused by improper alignment triggered by adding the weight of the coach onto the chassis. He implied that the alignment issue should have been addressed by the coach manufacturer, and he recommended a local tire shop to get the alignment corrected.

I took the unit to the recommended tire shop for alignment. When I picked it up the tire man told me that the issue wasn't the alignment, but was rather caused by underinflated tires. I had been running the tires at 61 psi (as per the tire pressure sticker on the door frame) but the tire man said that figure doesn't take into account the weight of the coach and I should be running the front tires at 70 psi and the rear tires at 75 psi.

I've taken the tire man's advice and increased the pressure according to his recommendations, but I'm curious about the validity of the advice I'm getting from the 'experts'. The owners manual for the motorhome states that the tires should be set to the pressure shown on the door frame sticker.

So, what's the best/most correct advice on tire inflation pressures for class C motorhomes? I'm confident that readers of this forum will be ready, willing and able to offer their opinions...

2017 Coachmen Prism 2250LE
2017 Toyota Corolla
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Old 11-27-2018, 10:50 AM   #2
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Motorhomes of any size are still motor vehicles and have the same tire wear issues and patterns of all motor vehicles. Wear on both edges is under-inflation.

If the door jamb cold tire pressure specification isn't sufficient boost it by (say) 5 psi. There's usually plenty of room under the maximum sidewall pressure as listed on the sidewall.

Check the cold tire pressure every morning the vehicle moves until you're confident the tires and wheels are maintaining pressure.

-- Chuck

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Old 11-27-2018, 11:16 AM   #3
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take it to a scale and get the actual weights then use the load inflation tables to get the proper pressure
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Old 01-02-2019, 08:57 AM   #4
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Wear on both the inside and outside edges would indicate under inflation. Wear just on the outside edges of both tires on the same axle would indicate an alignment issue.

Edit - updated after I realized that this is not a tow able - same general rules apply though.
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pressure, tire

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