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Old 08-09-2013, 09:03 AM   #1
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Tire Pressure and Handling

I own a 40' Country Coach Inspire DP. Going down the highway it has a slight case of the wanders. Not bad but noticeable. My question is does the front tire pressure play a role in this or is it just the road surface? The tires are 11/22.5's inflated to the recommended 120 PSI. The rears are inflated to the recommended 90 PSI.

Thank you any input.

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Old 08-09-2013, 09:09 AM   #2
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Hi Scoz,
The short answer is yes.

Both road surface and tire PSI can cause wandering. Gut feel says 120 PSI in the front tires is too much. The only way to determine the correct PSI is to have the coach weighed, when loaded for travel (water, propane, your stuff and you). Then make the PSI correct for the weight being carried.

I have 90 PSI in the rear and 100 in the front.

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Old 08-09-2013, 09:11 AM   #3
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GarryKD has is on the mark. Over inflated tires can make handling an issue. Load your MH and go get it weighed. Then check your inflation tables to see what you should be running. I know when I had my Class A I had the fronts inflated to max and if was all over the road. I weighed the coach and dropped them down by 15psi and it was a world of difference.
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Old 08-09-2013, 09:16 AM   #4
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Hi Scoz, tire pressure is definitely the place to start. Yes, your right thinking that road conditions could play a major part in your wandering. This is due mostly to large heavy trucks using the lane your in. If multiple lanes, move one lane over and see if the problem corrects itself.

Now back to tires, I find that 40' rigs won't have that big of pressure difference as your pressures indicate between front and rear, these types of pressures are more what you would find on a tag axle coach. Best way to determine real pressure for your coach is to weigh it (4 corner is best but not necessary), then refer to the manufacturer for the correct pressure, then add 5 psi for a safety margin.

If inflated to high for the weight, front tires can definitely cause wander.

Greg & Lynn (Full-Timing)
2011 Phaeton 42 QBH / Spartan Chassis
2003 Jeep GC Overland in Tow
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Old 08-09-2013, 09:21 AM   #5
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Tire pressure, alignment and ride height (which affects the front end geometry) are the main factors. Your CC should not wander at all, so something is awry.

120 psi is the max for most brands of 11R22.5, but probably about what is needed to support the front axle load on your coach. I'm running 11R22.5's on my rear axle, but don't use them on the front because even at max psi they lack sufficient load capacity for my front axle. Are they the original equipment tire on your coach? I'm guessing they are not, since they aren't common on motorhomes. Yours may have been 295/80R22.5 originally - the 11R22.5 is sometimes used as a lighter duty substitute for a 295/80.
Gary Brinck
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Old 08-09-2013, 09:42 AM   #6
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In a perfect world, chassis set up, no wind, and a flat road surface would lead to a perfect handling coach. Doesn't always line up that way.

Do check that you have the right tires installed on your coach, confirm air pressure by weighing your unit. Do this easy stuff first, then if not satisfied find a good reputable truck alignment shop and have a front and rear alignment done and have them check your ride height.

Doing all of the above may or may not fix your problem.

Greg & Lynn (Full-Timing)
2011 Phaeton 42 QBH / Spartan Chassis
2003 Jeep GC Overland in Tow
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Old 08-09-2013, 06:25 PM   #7
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Thank you very much everybody. I will get my rig weighed, check original tire specs and go from there. The help is much appreciated.
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Old 08-09-2013, 06:45 PM   #8
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I reduced pressure from 110 to 100 in my fronts and stayed well within safety range and handling improved noticeably.

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