Continental Tire PSI Rising 20 PSI

[sgtjoe]

I recently bought Continental 255/70R 22.5's for my Tradewinds, it has always ran Michelins but none were available.  I'm traveling from Southern Utah to Southern Arizona and am running 100psi in all 6 tires.  I have a TST TPMS that I've used since TST first started that monitors each tires temperature and psi.  The 100psi goes up to 120psi going down the road at 65mph.  Outside Temps were running high 50's/60's.  The Michelins never went up this much.  I don't think they ever went more then 6-8 psi, even in 108 outside temperatures.  My Honda CRV tow vehicle only gains 2 to 4 psi and these are with Continentals also.  My old Michelins were 14 ply and the new Continentals are 16 ply, could this be the cause???

Is there anyone on here who is running the same size Continentals with a Tire Pressure Monitor System that monitors PSI and Tire Temps??  One more thing my Tire temperatures were running a few degrees above the outside temps.  The tires were not hot at all, only problem is the 20 degree rise of the psi.

Thanks, Sgtjoe

[bm02tj]

The tire dealer did not have an air drier 

You may have to air down and back up with dry air a few times as the moisture is what causes the most pressure change 

[richard5933]

1 hour ago, bm02tj said:

The tire dealer did not have an air drier 

You may have to air down and back up with dry air a few times as the moisture is what causes the most pressure change 

Can you explain how this works? How would moisture in the air inside a tire have an effect this great on tire pressure increase?

[manholt]

Stgjoe.

What is the cold psi reading?  Like in the morning, before you leave Park.

[jleamont]

SGT, I have the exact same issue with my LR inner dual (my spare is installed). The LR inner dual on our coach is an off brand tire. The others are BF Goodrich, the off brand tire runs at a different Temperature and the PSI climbs higher than the others (around 10-15 higher). One would assume that tire in my case is carrying more load but the tread depth is the same as the other tires back there and I got so concerned I pulled it and measured the circumference of both LR tires.  

Are the Continental’s low rolling resistance tires like the Michelin’s were? 

In my case the spare was advertised as an eco tire but not to the quality level as the BFG’s were. The TPMS proves that in my scenario.

[wolfe10]

 How would moisture in the air inside a tire have an effect this great on tire pressure increase?

 

First, IMO, it is speculation that this is the root cause.

Could it  be-- CERTAINLY.

Nitrogen and "dry air" follow the Ideal Gas Law-- basically PSI rises at a given rate with increase in temperature.  Well documented since the 1800's.

BUT (large BUT) if there is water in there, water is clearly not a "gasses" and there will be a higher PSI rise for a given temperature rise.

And water could be in there from no air dryer on their air supply-- very unlikely as their air tools would live a very short life.  It could also be the lubricant that they may have used to install the tire on the rim.

[richard5933]

24 minutes ago, wolfe10 said:

First, IMO, it is speculation that this is the root cause.

Could it  be-- CERTAINLY.

Nitrogen and "dry air" follow the Ideal Gas Law-- basically PSI rises at a given rate with increase in temperature.  Well documented since the 1800's.

BUT (large BUT) if there is water in there, water is clearly not a "gasses" and there will be a higher PSI rise for a given temperature rise.

And water could be in there from no air dryer on their air supply-- very unlikely as their air tools would live a very short life.  It could also be the lubricant that they may have used to install the tire on the rim.

Agree that moisture being the cause is only speculation. I doubt that it would account for this large of a difference.

The amount of moisture contained in the air could never be high enough to affect the overall volume of air in the tire enough to cause pressure to rise as much as being described. I've read about air tanks or air bags which were half filled with water from never being drained exhibiting problems similar to this, but have never seen a tire with enough water to affect air pressure enough to be noticeable.

I have the rear tires on my tractor purposely mostly filled with liquid, and even when sitting in direct sunlight they never change enough in pressure to be a problem. Seems to me that they are more stable than the front tires filled with air only.

I'd suspect that the difference between the new tires and the old tires will end up being a difference in tire construction. Are they both the same weight rating?

 

[kaypsmith]

All above answers could be true, and I will also add tire tread design can be a factor, one tread design may offer more resistance to the rolling surface as opposed to another, and resistance can contribute to heat rise.

[rayin]

richard,  Daltons law defines the expansion rate of air that contains moisture.As previously stated, if no air dryer is used it  can have a profound effect on air pressure. We cannot ignore the fact that ALL tires are mounted at current atmospheric humidity, so some % of moisture content is always present, even when the tires are then pressurized with Nitrogen.

When I was in high school I worked part-time at the local Goodyear store as a tire changer. It was not uncommon to break down a tire and see an ounce or more of water in the tire.

[sgtjoe]

5 hours ago, manholt said:

Stgjoe.

What is the cold psi reading?  Like in the morning, before you leave Park.

My cold PSI is 100.  My Michelins were 235/80R 22.5 and these Continentals are 255/70R 22.5.  They are a little shorter then the Michelins, but not enough to affect my speedometer.  The width is less then 3/4" difference then the Michelins.  These were installed by a major Trucking dealer.

 

 

[sgtjoe]

If I raised the PSI from 100 to 110 would this affect the 20 psi increase on the road?

[richard5933]

18 minutes ago, sgtjoe said:

My cold PSI is 100.  My Michelins were 235/80R 22.5 and these Continentals are 255/70R 22.5.  They are a little shorter then the Michelins, but not enough to affect my speedometer.  The width is less then 3/4" difference then the Michelins.  These were installed by a major Trucking dealer.

 

 

If you changed tire size, then it's going to be really difficult to determine the cause here. Different tire geometry is certainly going to make a difference in how the tires react going down the road.

If the cold tire pressure is set properly for your weight according to the tire chart, then I wouldn't spend too much time trying to figure this out unless things suddenly change from the new baseline.

43 minutes ago, RayIN said:

richard,  Daltons law defines the expansion rate of air that contains moisture.As previously stated, if no air dryer is used it  can have a profound effect on air pressure. ..

Can you explain what you mean by 'profound' effect? Could there be enough moisture in an ounce or so of water to make the pressure increase 12-14psi over the other tires? Of course, the different tire size will make this comparison difficult as well.

[bm02tj]

https://www.theweatherprediction.com/habyhints/260/

this will help you understand why pressure will rise more with moist air 

[richard5933]

6 minutes ago, bm02tj said:

https://www.theweatherprediction.com/habyhints/260/

this will help you understand why pressure will rise more with moist air 

I get the concept - just questioning whether or not there is enough volume of air inside a tire of that size to make anywhere near a 12-14psi difference based on a slight increase in moisture inside the tire.

[bm02tj]

A better one 

http://www.longacreracing.com/technical-articles.aspx?item=70794&article=Tire Pressures - Cold to Hot

[rayin]

 

 

3 hours ago, richard5933 said:

If you changed tire size, then it's going to be really difficult to determine the cause here. Different tire geometry is certainly going to make a difference in how the tires react going down the road.

If the cold tire pressure is set properly for your weight according to the tire chart, then I wouldn't spend too much time trying to figure this out unless things suddenly change from the new baseline.

Can you explain what you mean by 'profound' effect? Could there be enough moisture in an ounce or so of water to make the pressure increase 12-14psi over the other tires? Of course, the different tire size will make this comparison difficult as well.

My apologies, profound was the wrong word, significant would be more suitable to the sentence and subject matter.

As to the size of the container, in this instance a truck tire, it is immaterial, as all ideal gas's have the same size molecules and occupy  the same space when at the same pressure. ref: Avogadro's Law

Normal pressure change is (where is tireman9)2% for every 10° tire temperature change-using dry air/nitrogen. You may calculate that for your specific tires, then factor in Dalton's law. (I'm not up to doing the calculations at my age)

Using SgtJoe'''s tires for the example, tires set at 100psi; 2% = 2psi for a 10° temperature change. Now assume his cold tires are at 60° before he begins a trip, an hour into that drive/trip his tire temperature is 120°, a 60° temperature change = 18° when hot- with dry air/nitrogen; then Dalton's law (water into vapor expansion rate) comes into effect to further change pressure.

I forgot, each brand of tire has different characteristics due to construction materials and methods, which is an un-calculable  variable to this subject.

 

[rayin]

3 hours ago, sgtjoe said:

If I raised the PSI from 100 to 110 would this affect the 20 psi increase on the road?

Read my reply to richard, I think I explained it correctly. The pressure difference would be small IMO. FWIW, my tires have such a pressure increase, IMO it is due to the tire shops air compressor "water trap" efficiency and level of  maintenance.

[manholt]

Personally, I would not worry about it.  Just see to it that your tires have the proper PSI to weight of coach.

[wildebill308]

I am with Carl. Set the cold preshure and go. The tiers are capable of handling any increase caused by heating.

Bill

[bm02tj]

Alot of things are ok to leave but if it is a simple fix with dry air I would look after it 

also high humidity inside tire is not good for the wheels 

try to find a shop with proper equipment and maintains it with clean dry air for there customers 

[richard5933]

In the end, this is not a complicated problem - if it's a problem at all. Assuming all four corners have exhibited a similar change from the old tires to the new, the change could easily be due to the change in tire size and/or the change in tire brand.

If you are concerned about possible moisture content inside the tires, call the shop that installed them to ask if they have an air dryer on their compressor lines. If their answer doesn't satisfy you or if you don't trust them, find another shop with a air line dryer and pay for them to purge and reinflate all your tires. Then let us know if there is any change.

[tireman9]

First off I would not be concerned about a 20 psi (or 20%) increase in your 22.5 tires.  Bet they are LR-G or LR-H

2nd yes air from a compressor can introduce some moisture that you will not get from the gas out of a cylinder.  It isn't the N2 that is dry as all gas purchased from a "Air Supply" or welding shop in cylinders are going to be almost 0% moisture.

While I haven't seen and test data, the N2 from local Nitrogen generators may have some low %moisture as they probably use better dryers than found at most tire shops.

3rd If you are running new tires they will run a bit hotter than older worn tires.  The 2% pressure for each 10F is close enough. Details and math can be seen HERE

 

You can always make and use your own "dryer" as seen HERE and if you support your tire with a jack you could let 50% out and re-inflate when you are in a dry weather day and dry location.

Just be sure your dryer is rated for the pressure you will be using. Be sure you have access to a good supply of high pressure air before you bleed off any air.

A quick check to see if this is even worth the effort would be to bleed off 5 psi and see if water drops or "fog" comes out of the tires. If not you don't have a lot of moisture in the tire to start with.

[sgtjoe]

Got a lot of different thoughts on this.  This morning I called the Dealer I purchased them from and he is going to contact the Continental Engineers and get back to me on what they might have to say.  When I get an answer I'll post it.

Today on my trip from Sierra Vista, AZ to Gila Bend, AZ the highest PSI was 118 on my TST Monitor,  starting cold psi was 100, outside temps were 60 degrees.   Tire temperatures never went above 78 degrees.

[bm02tj]

Did you ask what type air drier they have and if it is working 

[manholt]

How many miles do you have on them?  Avg speed?