Tire Pressure?

[thompsons 369rl]

I'm sitting in the Coachlight RV camp ground now where I bought my 303. I'm having some warranty work done, new table top and kitchen island doors. I asked about the tires. The tires say 65# and the sticker on the rig says 80#. The service manager called Grand Design and was told the sticker was not correct.

Wow! That's kind of a big deal IMO. I hope there aren't any more rigs out there with that mistake. Many of us rely on that sticker for proper inflation pressures let alone the fact that, if there were a tire failure due to over inflation, who's responsible for the damage it may cause? Let's hope GD is looking into this and notifies any other owners that may be affected as well as making sure this kind of error doesn't happen again.

BTW
Thanks, Jim for the article. Very informative.

[Retread68]

Interesting. My 2015 303 RLS #645 came with E rated tires (80 lbs). That was one of the positive factors in my evaluation of the unit.

Several years ago a tire mfg rep told me the major benefit of using N2 vs regular air was that the N2 would prevent tire rot occurring from the inside out as found with regular air due to moisture in the air. I've run a lot of tires during my years and I don't recall ever having one rot from the inside out; thus I just keep using that old fashioned air and hope it doesn't leak out !

[Mr Lucky]

That's always a tough one. It's one of the reasons I use a TPMS. When traveling, the temps can change drastically. One can only do their best to keep pressures at the rated spec. In extreme conditions, I have had the TPMS tell me there is a over pressure condition. I just pull over and let a few pounds out and continue on my way. Have never had it go the other way unless there was a leak. The TPMS helps take the guesswork out of the equation.

Today getting ready to leave for camping trip so first thing I checked was air pressure in cold tires and adjusted to 80lbs . It was very cool in the morning. I was on the highway doing 55-60 miles per hour and my buzzer was going off on my TPMS and my tire pressure was getting over 90 lbs in 2 of the tires. The other 2 tires were around 89 lbs. So I just pulled over and took out 5 lbs in all 4 tires. Also noticed the 2 tires in direct sunlight going down the highway had higher temperature in the tires. Once I was at my campground and my tires had cooled down I filled them back to 80 lbs. I like having a TPMS system. Just got it this year!

[Dave and Monica]

The tire pressures increase 10 to 12 psi from my observations when towing. If you check the TPMS manual, they should suggest settings for low and high pressure alarms. I think that you've got the high alarm set too low. I've set ours at 95 psi and have only had it alarm once when we had a 60^oF swing in ambient temperature the same day.

Dave

[Navigator]

Our TPMS manual recommends a setting of 20% above the cold tire pressure for the high parameter setting and 10% below the cold tire pressure for the low parameter setting. They also recommend leaving the temperature at the factory default of 158 degrees F. Our cold tire pressure is 80 psi so our high setting is 96 psi and low is 72 psi.

The following is from the TPMS manual...
Every brand of tire operates differently, when some brands reach operating temperature the psi will increase 5 psi, other brands may increase 20 - 22 psi.

We noticed that difference in psi when we had to replace an original tire with another brand. The pressure in the new tire was considerably higher that the other three original tires. Hope that helps!

Kathy

[TucsonJim]

Today getting ready to leave for camping trip so first thing I checked was air pressure in cold tires and adjusted to 80lbs . It was very cool in the morning. I was on the highway doing 55-60 miles per hour and my buzzer was going off on my TPMS and my tire pressure was getting over 90 lbs in 2 of the tires. The other 2 tires were around 89 lbs. So I just pulled over and took out 5 lbs in all 4 tires. Also noticed the 2 tires in direct sunlight going down the highway had higher temperature in the tires. Once I was at my campground and my tires had cooled down I filled them back to 80 lbs. I like having a TPMS system. Just got it this year!

Mr Lucky - I'd really recommend against bleeding off the pressure when the tires heat up. They are designed to be filled to 80psi cold, and the engineers who built them understand that the pressure increases with temperature. It will not hurt the tires when the pressure increases. Bleeding off air when they are hot effecively reduces the load carrying capacity of the tires. BTW, on my rig, the tires that are in direct sunlight always have higher pressure and temperature when going down the road.

[mtpocket]

I have to agree with TucsonJim. I set mine to 80 before I leave for the day. Sometimes I have to add and some days I may have to let some out. After that, as long as it doesn't go down while traveling I leave it alone. I don't pay attention to how high the pressure goes up on the road. I believe that is taken care of in the tire design. As long as both tires on the same side are within a few pounds and degrees I am not concerned.

[Mr Lucky]

Great info guys ,Thanks!

[RGMutchler]

The air or nitrogen we put in our tires is a gas and it increases or decreases with temperature in a predictable way. I don't run nitrogen so I have never looked it up but the atmospheric air we put in our tires increases or decreases in pressure about 2% for every 10 degrees. When you run down the highway the temperature in the tire increases or decreases based on ambient air temp and due to the friction created by the tire on the road. For a load range E tire rated at 80 PSI cold that would mean 1.6 pound increase or decrease in pressure for every 10 degrees of temp. Consequently, when the temperature is 60 degrees one morning and you set your pressure at 80 psi but 40 degrees the next morning you will need to readjust the pressure because it will be a little more than 3 degrees lower than it was the morning before at 60 degrees. As to the max pressure I have yet to get any of the tire manufacturers to publish or state a max pressure or a max temperature for their tires. When I have talked to the Tire pressure sensor folks and asked how they arrived at 20% or what ever the different ones recommend they are unable to tell me where the 20% number comes from.
I hope this is useful.

[ruskin219]

Check out what is said on the internet about nitrogen filled tires. They do run cooler and supposedly stay inflated longer but basically if you're not a race car driver, nitrogen filled tires are an income generator for tire stores and not needed for consumer application. The good news is that when your nitrogen filled tires need to be brought up to pressure, you can simply add air.