how to inflate hot tires?

CHICKDOE · 07-19-2015, 06:32 PM

been wondering about this for a while. all the instructions are to measure the tire psi when it is cold and inflate it to the desired psi when it is cold. how many rv parks have a tire inflation station? I must have missed them in the parks we have stayed in. so I can measure the psi at the park while the tire is cold. but how do I inflate it? if I tow down the road 50 miles or so to a truck plaza the tires are then hot. the only thing I can come up with is to measure at the part while they are cold and calculate the additional psi needed to bring them to the desired cold psi. then when you get to a place to do the actual inflation you would measure the current hot psi and then add more inflation to it based upon the calculation you did when they were cold. is this the proper way? is there another way? any other ideas?

rsdata · 07-19-2015, 06:38 PM

12V battery operated (to your TV plug) tire inflation machines are not that expensive... I always carry one to top off tires when I am leisurely at the campground checking things

Ford Idaho · 07-19-2015, 06:43 PM

Many here carry a air compressor.

http://www.google.com/url?sa=t&rct=j...sZuTGPjRKQkZcQ

**Herk7769** · 07-19-2015, 06:46 PM

He is asking about filling a hot tire vs a cold one.
All the specs are for cold inflation pressure.

The answer of course is "you don't"

Setting the pressure "hot" will result in a severely under inflated tire. It is not unusual for the "hot" pressure to be 5 to 10 PSI above the cold inflation temperature depending on outside air temperature at the initial fill.

That is why most campers carry an air compressor.
Mine is a low profile Dewalt.

DEWALT 1 gal. Portable Electric Trim Air Compressor-D55140 - The Home Depot

It runs just great on my 1000 watt inverter!!!!

n-e-d · 07-19-2015, 06:57 PM

Ditto on carrying a compressor. I know thats not the answer you might have been looking for but it would be a solution even a small 12v would help. I carry a small 110v compressor for coach, toad and bike tires and air bags

rsdata · 07-19-2015, 06:57 PM

Quote:

so I can measure the psi at the park while the tire is cold. but how do I inflate it?

I think you have your answer

http://www.amazon.com/Black-Decker-A...KFAS1FADM7MNAS

**wmtire** · 07-19-2015, 07:21 PM

The unwritten rule of thumb we use in the tire business when setting pressures on passenger tires, is that every 10 degrees of ambient temp change equals about 1 psi. Air expands when it is hotter and contracts when it is cooler.

High pressure tires can be anywhere from 1.5 to 2 psi per 10 degrees of temp change.

Now this is just ambient temp, and not internal tire temps which could be higher than ambient after running for awhile.

An example for a passenger tire would be say it's 80 degrees that afternoon, and the tire calls for 35 psi. The cold temp would be say 60 degrees in the morning. So if we put 37 psi in the tire at 80 degrees, then the next morning it should read 35 psi cold.

What has become fun for us (sarcastically spoken) is the TPMS sensors. When we have an overnight cold snap come in where ambient temps may change 40 degrees or more overnight...then the pressures drops 4 psi or more. Many people already had tires not quite up to pressure, and losing 4-5 psi make the tpms light come on. I can't tell you how many people we get when this happens thinking their tires have punctures.

You want to check your tire pressures frequently, as ambient temps through out the year will be one contributing factor

cpaulsen · 07-20-2015, 07:23 AM

Check it when cold......then when you get to a station...put in the right amount of air.

banda · 07-20-2015, 07:48 AM

From Tire Rack:
Tire Heat Generated While Being Driven (or at speeds of less than 45 mph).* Set 4 psi above vehicle manufacturer's cold inflation recommendations.
Heat Generated While Being Driven Extensively (or at sustained speeds greater than 45 mph).* Set 6 psi above vehicle manufacturer's cold inflation recommendations.

acadianbob · 07-20-2015, 07:51 AM

I've put air in a hot tire. Sometimes you have to . . .

I figure it a couple of different ways.

1) Cold pressure plus 5 PSI

2) Measure the hot PSI of an equivalent tire on the vehicle and match that.

Pipeman · 07-20-2015, 08:15 AM

I carry 2 compressors. One is 110v and the other is 12v. I've never seen a campground that provides air service but I'm sure there are some. Just tried the 12v one out last week and it had no problem bringing air pressure up to 80 psi.

mcnabbwr · 07-20-2015, 08:25 AM

As a last resort if you have a tandem axle unit, take the average of the remaining three tires and inflate to that hot pressure.

Jim34RL · 07-20-2015, 08:26 AM

Quote:

Originally Posted by wmtire

What has become fun for us (sarcastically spoken) is the TPMS sensors. When we have an overnight cold snap come in where ambient temps may change 40 degrees or more overnight...then the pressures drops 4 psi or more. Many people already had tires not quite up to pressure, and losing 4-5 psi make the tpms light come on. I can't tell you how many people we get when this happens thinking their tires have punctures.

I have eliminated that problem on my TV. No TPMS sensors in the wheels, black tape over the idiot light.

I do know how to use a tire inflation gauge and I check the tires on my vehicles monthly and the trailer daily when towing.

jk510 · 07-20-2015, 10:09 AM

Measure your tires cold and then when you get to a station just add the amount that you were down. It may not be the most accurate method but it's better than running low. Being off by 1 or 2 psi won't be catastrophic.

CHICKDOE · 07-20-2015, 10:10 AM

thanks for all the info, really appreciate it. looks like a small 110 volt compressor might be in the works. they say they will supply 100+ psi? (our tires are max 110 psi but I plan to run them at 100psi). i have 110 outlets on the outside of the trailer. plus a 110 inverter in the truck. again, really appreciate the feedback!!!!! we're new to this (but learning real fast). I've learned a lot from many of you and i THANK YOU!

B and B · 07-20-2015, 10:18 AM

Quote:

Originally Posted by Jim34RL

I have eliminated that problem on my TV. No TPMS sensors in the wheels, black tape over the idiot light.

I do know how to use a tire inflation gauge and I check the tires on my vehicles monthly and the trailer daily when towing.

I do use the Truck built in sensors. Nothing on the trailer at all, Use a temp gun and shoot the tires and hubs when travelling to look for problems.

I have a 40 year old Coleman Compressor and 30 ft 12 v extension cables.

OldCoot · 07-20-2015, 10:34 AM

Quote:

Originally Posted by jk510

Measure your tires cold and then when you get to a station just add the amount that you were down. It may not be the most accurate method but it's better than running low. Being off by 1 or 2 psi won't be catastrophic.

X2, good advice.

mud yapster · 07-20-2015, 10:57 AM

While hot I would just inflate to the recommended tire pressure then the next morning when they are cold check them again and adjust the pressure accordingly.

Airdale · 07-20-2015, 02:29 PM

Normally the need to air tires when they are hot is because you discover them under inflated.

The rule of thumb is to then air them to the recommended pressure depicted on the placard. Then again when they are in the cold condition.

kluza2786 · 07-20-2015, 07:30 PM

I bought a unit at Costco that is a combination tire inflator, battery jump starter, and USB charger. The advantage of this is that it has a built-in battery so that you aren't fooling with power cables, etc. (assuming that you keep the battery charged on it). When I want to air up the tires on the trailer, just carry it back and hook up the air line. I think it was about $ 50.00 or so and has been real handy for both tire inflation and jump starts.

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