Talk to me about tire pressures

[russue125]

I'm a widow trying to figure everything out on my RV, a daunting task. I know how to check my tire pressure but where can I get someone to pump them up if needed?

[Jake21]

Originally Posted by russue125

I'm a widow trying to figure everything out on my RV, a daunting task. I know how to check my tire pressure but where can I get someone to pump them up if needed?

Are you in a RV park? If so, I would ask any neighbor in a class A to help.

[Mr_D]

Amazing how many people answering here have never read the manuals put out by tire companies.

The pressure on the sidewall of a heavy duty tire is NOT the maximum cold pressure. It is the Minimum cold pressure to support the maximum rating of the tire. That's the way the weight/pressure charts read too.

[RonLC]

Originally Posted by russue125

I'm a widow trying to figure everything out on my RV, a daunting task. I know how to check my tire pressure but where can I get someone to pump them up if needed?

I drive over to the Goodyear Tire store, which has the largest parking area of my local tire stores, and pull in the back blocking all the bay exits. When they notice me one of the techs will ask me what I want. If he is grumpy it may take a few minutes but they will eventually do it. It the guy is very willing, I tip him 10 bucks.

This Goodyear store is only a block a way from my covered storage yard so the tires are still cold when I get there.

[Terry L T]

Jake21 the answer according to your weights and the chart looks like
90psi front = 12,440# / 85psi =11,880#
85psi rear = 21,060# / 80psi =20,060#

[Terry L T]

russue125, if your tires need air occasionally I would carry a small 120v compressor capable of at least 150 psi I carry one from Lowes. Like someone else replied, someone in your rv park will have a compressor

[Walt Graham]

Try to stick with the chassis required psi per tire or a few pounds over if you don't know the applied weight per tire location. All tire manufactures show the maximum psi per tire on the tire sidewall and this is for the most weight the tire can carry at that value. Remember it is better to run a tire hard (at a higher psi) than soft (low psi) due to potential heat cycling of the tire that will cause the tire to fail.... these are the big black chunks you see along the highway and in most cases they are fairly new tires and not recaps.

[edge68474]

I'm wondering here, how is it, on a crowned road, that BOTH the inside duals carry more weight than the outside?, as mentioned before.

[Tireman9]

Originally Posted by Jake21

Are you 100% confident of this. “ALL”?

From Michelin: “Michelin displays tire loads per axle end in the load and inflation tables. We recommend weighing each axle end separately and using the heaviest end weight to determine the axle's cold inflation tire pressure. For control of your RV, make sure tire pressures are the same across an axle, while NEVER exceeding the maximum air pressure limit stamped on the wheels.”

My front Axle is 11,480. GVWR for the front it 13,700
My rear is 20,200. GVWR for the rear is 20,000. (Since weighing I shifted some weight forward)

According to the placard my psi should be 120 front and 100 rear.

According to Michelin my psi should be 85 in the front and 85 in the rear. I run about 5 psi higher.

Am I wrong? I always like a second brain checking my math.

FYI: My placard lists Michelin XZA1energy, I have XZA2 energy.Attachment 239513

Ok, I finally looked at your post closely. Some things are confusing (terminology)

Is your Front GAWR (not GVWR) 13,700 and front scale weight 11,000?
Is the rear GAWR 20,000 and your scale weight is 20,000?
If so you still need to shift some weight off the rear axle.

To avoid the confusion of the Michelin chart where they " displays tire loads per axle end in the load and inflation tables." let's talk individual tire.

Your XZA2 295/80R22.5 LR-H tires would need 110 psi to support a load of 6,850 or 80 to support 5,500#

On the rear, they need 90 to support 5500.

B U T
The above does not allow for any side to side load variation from a perfect 50/50 end to end split.
I suggest you assume an unbalance of AT LEAST 53/47 with 55/45 possible

I also suggest a +10% on the inflation above the minimum is shown for the load used in the tables.

While I have covered this numerous times on my blog, sometimes with detailed actual loads and inflations given.
I would offer that you run the tire placard inflation until you get actual "4 corner weights"

If you want to take a chance then assume that the heavy end of each axle has 53% to 55% of the truck scale weight and use the table to learn the MINIMUM cold inflation then add 10% to that number without exceeding the tire max or wheel max to learn tour cold "set" pressure.

[Tireman9]

Originally Posted by edge68474

I'm wondering here, how is it, on a crowned road, that BOTH the inside duals carry more weight than the outside?, as mentioned before.

How did you get scale weights for just the inner dual tire? What is the scale weight difference you are measuring?

[Tireman9]

Originally Posted by Mr_D

Amazing how many people answering here have never read the manuals put out by tire companies.

The pressure on the sidewall of a heavy duty tire is NOT the maximum cold pressure. It is the Minimum cold pressure to support the maximum rating of the tire. That's the way the weight/pressure charts read too.

^x2

[RonLC]

Originally Posted by Tireman9

I would offer that you run the tire placard inflation until you get actual "4 corner weights"

Tireman9: I humbly bow to your knowledge. Thanks

It will probably be a long time before many of us get around to a 4 corner weigh.

[Tireman9]

Originally Posted by 777 Driver

Hi Kevin,

You're right, it doesn't seem like a good idea to use an inflation chart for Hankook tires to select the appropriate inflation for your Bridgestone tires.

I have to admit that Bridgestone doesn't make it easy to find their inflation charts. But, perseverance pays. I was able to locate this link to Bridgestone inflation tables: https://commercial.bridgestone.com/c...08-08-2018.pdf

Although a "four corner" weigh is best, an axle weigh would be better than nothing. The challenge with the axle weigh is that it leads you to make an assumption.

Here's an example:

Left front - 4,000#
Right front - 6,000#
Total front axle - 10,000#

With the Cat scale (axle only) weight slip, you would probably be inclined to set your tire pressure from the Bridgestone table based on a 5,000# load on each tire. That would lead you to having an under-inflated tire on the right front and over-inflated on the left front. That's not a good thing since under-inflation is a frequent cause of catastrophic tire failure.

With a "corner weigh", you'd be lead to inflate the right front to the pressure appropriate for a 6,000# load (perfect inflation) and follow the recommendation that all tires on any axle are inflated equally. Although that would leave your left front over-inflated for its load (4,000#), that's generally accepted practice.

There are many variables that can lead to different weights on the opposite ends of the same axle. Some of those reside within the design and manufacture of the coach; some are due to the way you load it. Just how much difference there is and how much difference that all makes on appropriate inflation is hard to say. That's why you'll see general consensus that a "corner weigh" is much preferred.

Take care,
Stu

If you compare identical size and same Load range I believe you will find that all tire company charts give the same numbers EXCEPT Michelin and then they are different on only a couple of sizes that were originally designed for Eureopean use & roads then introduced in the US. Those differences are also usually withing one 5 psi range of each other.

[Tireman9]

Originally Posted by Terry L T

I would also look at the max pressure listed on the rims, I think my Alcoa rims say 120 # cold max if i'm not mistaken. Also with the TPMS, you can watch tire temp if not in the sun. I watched to see if the front and rears are about the same temp while running down the road, after I got a new set in the front, to insure that I have the pressure correct front and rear. I also use the TPMS to check the tires before every start up, I give myself enough time, in case I need to inflate after it has been in storage.
When I bought the used Beaver I found that the inside dual on the drivers side had a steel rim (probably from a blowout). The significance of this is that, that tire changes pressure and temp differently than all the rest. My coach has a 12,800# front axle and 20,000# rear axle, yours could be similar, I run 105# front and 95# rear since I am always at max weight, but you probably have larger tires because an '04 Beaver like my '03, has the next size up tires with the same axles, mine are 275/70R22.5. Front are Hankook, rear are Hercules. The Hercs had to be replaced on the front because there were cracks between the tread on both tires running at 115# to carry the max axle load, per their load table. The new Hankooks at 5 psi lower run the same temps but have a better ride. I am kind of anal about the tires and have balanced them so the temps are the same front and rear, this might be a mistake but it looks right on the monitor. If the fronts are colder running than the four rear tires I would think they had too much air and if they were hotter than the rears they would be under inflated. I know the rears are correct for the max load. Also the handling goes away when the rears have a lower pressure. Just my two cents.

If you have one dual performing (temperature rise) significantly different than the rest of your tires and it looks like it was a replacement then I would STRONGLY suggest you have the OC MEASURED FOR MOTH TIRES AT THAT END OF THE AXLE .(mEASURED WHILE FULLY INFLATED BUT NOT LOADED)
should be =/- 3/4"


Details here and in the links