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Old 07-11-2010, 03:20 PM   #1
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Question Tire presure question

I did search the threads for a answer, but didn't find one, but I could have missed it.....

I guess it is not the most important question but I would like to know what others do.

Question........Do you adjust the (cold) tire presure when you go from a cold climate to a hot one ?

Example...I set my TT cold@48lbs in NY with temp.of 35degs.
Then get to FL and temp. is 85degs. Do I reset the tire pres.?
I have not done so in the past, but the tires are now (when cold) @85degs. higher than the 48lbs. set in NY@35degs.

Thanks
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Old 07-11-2010, 05:46 PM   #2
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I will adjust mine once heading south or north. Having a TPMS I always know what they are. If I'm heading south and get an "over 50" reading first thing in the morning I'll let 2 psi out reasoning it's only going to get hotter. I am also 1000 lb. under on the GVWR so starting out at 47 or 48 psi is not a problem as the tires don't have to carry their max. load. On a typical warm, but not hot, summer day the tires run at 55-56 psi at 60 mph. The highest reading I've seen is 59 psi on the sunny side on fresh asphalt on a hot day. We only go to the Pensacola area in Mar. so don't see really hot temperatures on our way south. If I was going to Miami, I'd probably set the pressure once more.

Since the tires can easily run at 59 psi and 47 is good enough for my load, we could probably get away without any resets on a spring trip.

Tire pressures change with altitude too. Crossing the Rockies we've also found it doesn't make a big difference and the tires have enough leeway here too for the ups and down--8-9000 ft passes is the highest we've been. Plus you drive a lot slower going up and down.

Henry
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Old 07-11-2010, 07:22 PM   #3
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Hi Joe

Good question. I’ll add some here but it may have been from a different point of view. Henry’s response and him having a tire pressure monitor helps validate my thoughts.

I myself have not yet had the “wish” come true to take off at home here being at freezing and then heading to TX or FLA. Some day, it will happen. YEH!!!

But I do do something similar. We winter camp. When we head out in January it can be below freezing or at freezing. During the day it might get up to a whopping 35 maybe 40F. I’m a real stickler for every trip to check tire pressure on the TT and truck and I adjust it for that time of year. The 1st winter trip may have been 1 month or more from the last outing. That time length will force me to add air back to max cold side wall pressure on the TT. The truck I run at 65 front and 75 rear but they are 18” tires and a 1 ton truck so pressure it relative here. Since I am not going to extremes of temp swings the pressure I left with is still OK for that trip. And the next trip I reset again as needed.

Spring time here in our area seems to be a yoyo with temps and for sure the tires follow the same yoyo. One week I’m adding, the next 2 weeks I subtracting then the next 2 weeks I’m adding again.

Since your good question came up it made me think, well what would I do? I myself would reset as needed on my daily pressure check. We would not travel much more then 400 to 500 miles in one day and that much change I should be OK providing I reset at the start of each day.

Good question. And another good plus to help support a tire pressure monitor system. After my ordeal this past weekend with tire pressure…errr. A monitor system may be on Santa’s list this year. For a long trip out west I for sure will have one.

Hope this helps.

John
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Old 07-12-2010, 01:53 PM   #4
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Thanks, Henry and John for the replys with the helpfull information.

I think I will just continue to set the pressure @48lbs. when traveling from NY to FL.

Henry, you said if it goes to 59lbs.it's fine for the 50lb sidewall rating tire.
I read in one of the links that a tire will gain 1lb.pres. for ea.10degs.in temp.
So 48lbs.@ 35degs.will only gain 5lbs.@85degs. to 53lbs. then there is no need to let air out, (it's not near 59degs.)......should be fine right ?

I am thinking of getting a tire pres.monitor system for the Que. I have a factory one on the Tahoe and it's great.

BTW
John, what happened to your tire pres.? You said " After my ordeal this past weekend with tire pressure…errr."
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Old 07-12-2010, 08:17 PM   #5
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You may have read this Tirerack article on temperature effects. There are 2 temperature effects on psi: ambient temperature and moving tire temperature. They don't directly add them up, but if you are driving south at high speed you'll see both effects and could hit 60 psi. My TPMS is set to send alternating pressure and temperature signals. I don't have a good sense for where the temperature is at though because it just doesn't register--like looking at the oil pressure gauge. The temperature does vary some during the day and that's also why I couldn't say what it is without actually checking the next time and writing it down. The TPMS does have a high temperature alert and will override a pressure display even if it is not set to display temperature. The factory default is a warning at 80°C (176°F); user adjustable to 99°C (210°F). I know I have seen tire temperatures over 40°C, but really can't say whether they have been 50°C+.

Doing some Googling I can't find a definitive answer as to what tire temperatures are still acceptable and of course it would vary with tire construction and A, B or C temperature ratings. It looks like 150°F is still ok. So, going from 50 psi at 50°F to 150°F would give 60 psi. My TPMS is also marketed for race cars which might explain the higher temperature warnings.

In any case, it's important to remember that tire pressures should always be set cold. If driving all day on a hot day sends the pressure up to 60 psi, so be it. The tire manufacturers claim the tires are built to take what ever temperature nature throws at them as long as we don't overload them or drive too fast.

Henry
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Old 07-12-2010, 08:46 PM   #6
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Quote:
Originally Posted by luvrque View Post
BTW
John, what happened to your tire pres.? You said " After my ordeal this past weekend with tire pressure…errr."
Hi Joe

There has been a lot of tire pressure activity here lately on the forum… so I’ll throw my latest story in.

I diligently every time I head out check the truck and TT for pressure and reset as needed. And last week with the holiday I was all loaded up Thursday night before the 4th holiday trip. Cindy had the truck over at the grand kids place kid sitting late so I did not hook up yet. Figured all I had to do was hitch up and check pressures. A whole 15 minute job….right….

So Friday came, got out of work early no less and ready to hitch up. Checked the truck for pressure and all where good. Then the TT. 65 psi, 65 good that side is dead on like they do stay in the summer. Then went to the other side. 45, and 65. What??? Must of read that wrong. Yup it is for sure 45. Oh great…. So I looked over the entire tire for a nail or screw in it. Nothing. I felt and listened. Nothing. The TT was in the same place for 2 weeks never moved. If it had a nail in it, it would be flat by now…. So now what. Friday out of work early, ready to go, wife getting ichy… I did the film of water over the valve stem trick to look for a leak and nothing. OK pump it up and lets go. I’ll check it during the trip.

So I pumped it up and off we went. Got 20 miles down the road and pulled off at the rest stop. By then it had heated up was at 70 and the other one that side was 72. The 2 psi could be a little bit difference due to my slider pressure gage. Since it was still above 65 I kept going.

Made it to camp OK. Had a great time other then the 98F heat… 4 days later I hitch up and say I better check that tire. Yup its now down to 58. Oh great. The State Park I was at was a day after everyone left. No ranger around and I had no onboard compressor. Have a complete tire plug kit, just no air…

OK the gas station in town 2 miles away has air. Going slow also on the back roads pull into the gas station that is like a bee hive….. a truck is parked next to the air pump. Pull the hose out, 3 feet to short… Oh great. So I pulled out and started looking for the next one. Pulling a 33 foot camper one has to be a little selective. So I spotted a car wash and out side a hose and what looked like a air hose. Pull off to the side of the road, waiting 5 minutes for traffic to clear and headed to the car wash. Pull in, made sure I can get back out of there…. Get out look at the hose. Darn thing is some kind of car freshener chemical you spray in your car….. Oh great no 2. So I manipulate the rig out of there and head back down the road looking for another station. This little town is not conducive to a large TT… So OK I’ll head 5 miles up the road to the Interstate exchange where there are truck stops and more gas stations.

Get to the truck stops. A Pilot. The semi area is blocked off with trucks coming and going and the gas pumps like a beehive…. OK past that one. The BP, ah nope I’m not getting in there. So I keep going to turn around in a big parking lot of a restaurant and go back to the Pilot. Well to keep semi’s out they stuck a post dead smack in the middle of the driveway. Well nope, not turning around in there. Blood pressure now up a few points…

So, now down the road we go. Have no clue where this road goes and I’m now out in the country…. Cin, break out the maps and tell me where this road goes. She is digging in the maps and there is no where to pull off, so I keep going.

I come around the bend and there is a John Deere equipment dealer. YES, I know this kind of place! Being a farmer in past life one knows equipment dealers. So in we go. Went into the service manager and plead my case…. After talking old times…. He said pull around to the side for some air. I said I have a camper and truck the size of a small semi. He says no problem that back area is all gravel and we unload combines back there, lot of room. So off we go. Turn around and stop by the shop door.

Walk in, 2 guys rebuilding a tractor come over and say can we help you. Told then the deal on the service manager and needing air. They said sure but got to find a air chuck… So they pulled the hose to the camper and said they have no tire gage but have a tire air chuck. That’s OK I have one… Checked the good one, added 10 psi to the low one and now I’m back in action.

Asked the guys, how much I owe you? They said nothing. I thanked them big time and off we go…

We made it home OK and took the tire off and hose soaked the whole thing. Nothing on the tread or tire. Good as these are brand new last spring. Then wiggled the valve stem. Ah ha!! There is a slow leak around the valve stem to the rim. Took it to the tire shop. They put in a new stem, charged me $25 and on my way I go.

Learning from all this?
  • Having a big camper and trying to find a air hose that can go up to 65 is a challenge. 80 psi on the truck is even more a challenge.
  • This kind of valve stem leak can be as bad as a nail in creating a real bad situation. Even though I religiously check tire pressure every day when towing, this can occur in the middle of a long day towing and then I got problems as going down to 45psi on my rig is an issue. A tire pressure monitoring system for sure has merit on a TT. Especially a single axle like your Que.
  • Yesterday, I now bought a small compressor that will live in the camper. It’s a 120 VAC unit with a 2 gallon tank. The small air nailer kind. It’s not the top of the line but will work to get the truck tires up to 80 if I need it too as it is a 100psi shut off. My small inverter can run the motor if I have to and when I have the generator with me or at camp it’s not a problem. At home I have a big one so this one is only for TT use or playing with around the house. I was afraid of those little 12 volt jobs burning up trying to inflate a truck tire.
  • Having a tire plug kit and no air tank does not do one much good in the middle of no where…
  • In over 22,000 miles of TT towing alone, a tire issue on the road has never occurred to me. So my preventive actions have helped but the frustration of last Tuesday was enough to drive me to getting a portable compressor. And seriously think about a tire pressure monitor.

Good luck on your unit.

John
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