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Old 08-19-2017, 01:17 PM   #1
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Changing tire sizes

Would changing from 275\70 22.5 to a 295/70 22.5 and running less air pressure make a significant difference in ride and/or handling on a 40ft coach?
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Old 08-19-2017, 01:37 PM   #2
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Would changing from 275\70 22.5 to a 295/70 22.5 and running less air pressure make a significant difference in ride and/or handling on a 40ft coach?
Oh yes it sure could. Lower tire pressure can and will cause the tire to squirm when under way which will lead to a build up of air pressure which can cause a tire to blow or damage to tire sidewalls which will also lead to failure of the tire.
Follow the recommended tire size recommendation and keep the tire pressure within the recommended specs. and be safe.
Nothing to be gained but a lot to lose by trying to reinvent the wheel. (pun intended)
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Old 08-19-2017, 02:29 PM   #3
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Oh yes it sure could. Lower tire pressure can and will cause the tire to squirm when under way which will lead to a build up of air pressure which can cause a tire to blow or damage to tire sidewalls which will also lead to failure of the tire.
Follow the recommended tire size recommendation and keep the tire pressure within the recommended specs. and be safe.
Nothing to be gained but a lot to lose by trying to reinvent the wheel. (pun intended)
Lynn
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Old 08-19-2017, 02:38 PM   #4
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Would changing from 275\70 22.5 to a 295/70 22.5 and running less air pressure make a significant difference in ride and/or handling on a 40ft coach?


You could also go to a 275/80 load range H which would carry 7160 pounds at 120 psi. 6435 pounds at 105 psi. It really depends on how much room you have in your wheel well.
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Old 08-19-2017, 02:40 PM   #5
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On our 2002 DSDP I went from 275/70's to 305/70's on the front with wider aluminum wheels. The tires are wider than the 275's and have about the same weight rating as the 295/80 tires.
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Old 08-20-2017, 11:36 AM   #6
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The handling will be the same on both sizes as long as the inflation is correct for the load. There is no real advantage in increasing tire size solely to run a lower pressure because it will be proportionally the same if tuned for the weight load. However, if you run the psi shown on the RV manufacturer's tire placard, you may benefit from a weigh-in and adjustment of that psi for the actual load.

The reason is simple. The tire must have enough air in it so that the square inches of rubber in contact with the road x the psi is enough to carry the weight on that tire. If barely enough, the tire is "soft" and it squirms around and the sidewalls roll over in turns. If somewhat greater, the tread stays flat on the road and the sidewalls stand nicely and handling improves. If too much, the tire gets hard and bumpy, plus it is prone to skidding. That's true no matter what the tire size is.

My advice is to keep the OEM tire size and tune your psi to the normal load, plus a little for a safety margin. Get to the scales and weight the coach axle by axle or "4-corner" (tire by tire).
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