Tire pressure load rating

[Chief Deputy]

We took our 2015 Ventana 4037 to get her weighed today. I have attached a photo of the weigh ticket and the Continental tire load rating.

From what I understand, it appears the front tires will need to be at 95psi. My question is how do I figure the drive axle weight between the duals and tag? I divided the steer axle weight by two. If I divide the drive axle by six I'm not even on the chart.

Any guidance is appreciated.

[clawsonbob]

Could you assume 2/3s of the total rear weight are being supported by the 4 tires on the drive axels 4 tires and the other 1/3 of total weight on the tag tires. But if/when you dump the air in the tag, you are bearing the rear weight on the 4 drive tires, so that should be your max weight per tire in the rear. Flame suit on-this is likely to be a lively discussion

[Dutch Star Don]

Your chart is blurry and hard to read, but when you figure out the pressure for the rears, you use the DUAL numbers, not the single. So you divide the front by two, which is 5900 pounds. Find the correct air pressure under SINGLE and round off to the next highest weight/number.

On the rears, when divide by two, your weight is 11750 per side....find that weight under the DUAL column for your tire size, again, rounding up.

[dbircky]

Go back to the scales and get a weight for each axle. Depending on the air in the tags the weight might not be evenly spread across both axles. Make sure your fuel is topped off and the amount of water you plan to carry is in the tank.

[Chief Deputy]

Your chart is blurry and hard to read, but when you figure out the pressure for the rears, you use the DUAL numbers, not the single. So you divide the front by two, which is 5900 pounds. Find the correct air pressure under SINGLE and round off to the next highest weight/number.

On the rears, when divide by two, your weight is 11750 per side....find that weight under the DUAL column for your tire size, again, rounding up.

DS Don,

I tried that but the dual chart shows a max load of 6940. How do I factor in the tag axle which is a single?

[mbrooking]

You'll need to separate the axles on different areas of the scale to get a separate weight for each axle. Now that you have the steer axle, don't worry about that and just have the drive and tag axles on separate pads.

[stang37]

This may not help you. Based on my weights per axle/tire position the tag tires carries about 1/2 the weight of the duals. I have two separate CAT scale weights checks which are combined duals and tag. Both are within 1K of each other. I also have two individual tire weights checks which are within 1K of each other. The CAT and individual weights checks for the dual/tag tire weights are within 1800# across the 4 weight checks. Based on these my tag tires runs about 1/2 of what the dual tires carry.

[Chief Deputy]

I've been researching previous posts regarding the Continental load/pressure table. I see other people have the same problem with the "dual" portion of the chart. No matter how I try and break down the weight numbers for the drive axle I can't find it on Continental's table.

Stang37,

Out of curiosity, what pressure do you run in your duals and tag? The previous owner of my coach said he ran 95psi in the steer axle and 90 in the duals and tag. 90psi just seemed a bit low to me.

I might try and contact Continental soon. I just need something reasonable until i can get the manufacturers recommendation.

[TJ]

Originally Posted by Chief Deputy

Out of curiosity, what pressure do you run in your duals and tag? The previous owner of my coach said he ran 95psi in the steer axle and 90 in the duals and tag. 90psi just seemed a bit low to me.

Our 2018 Mountain Aire is significantly heavier than the Ventana listed in your profile and we run 90 PSI in the drive and tag tires, even though Newmar said we could run 85 after they weighed the coach during our last visit to Nappanee. If the tire manufacturer’s pressure chart for the scale weights (and, you should have individual weights done for the steer, drive and tag axles) indicate 85 psi is safe, it is.

I like DS Don’s rounding up idea (which is what we did when Newmar recommended 85 psi); it gives you an additional safety cushion. So, if you feel 85 psi is too low, move up to 90 psi and be confident that you are safe. I’m guessing that when you get individual axle weights on your coach, it may well be that 80 psi is acceptable; 85 psi would give you just a bit more of a safety factor.

Above all, don’t guess at axle weights and tire psi; get the individual axle weights of your travel-ready coach and use the charts.

TJ

[Dutch Star Don]

Originally Posted by Chief Deputy

Your chart is blurry and hard to read, but when you figure out the pressure for the rears, you use the DUAL numbers, not the single. So you divide the front by two, which is 5900 pounds. Find the correct air pressure under SINGLE and round off to the next highest weight/number.

On the rears, when divide by two, your weight is 11750 per side....find that weight under the DUAL column for your tire size, again, rounding up.

DS Don,

I tried that but the dual chart shows a max load of 6940. How do I factor in the tag axle which is a single?

Sorry....I didn't see that you had a tag. You need the tag weight, figure as a single and then do the new dual numbers, under the DUAL chart.

You can email Newmar and get your weight as the coach came off the assembly line. They'll give the numbers for all three axles. They'll be pretty close on the weight of your tag.

[Algoma]

I had all my corners weighed individually and verified that the tag is set to 50% of the dual drive wheels. In that case all six tires at the rear carry the same load. When I checked the Michelin pressure charts I could safely inflate my tires to 80 psi, which is the minimum pressure the XRV tires should be inflated to. From the initial post it appears the coach has Continental tires, which must be Urban HA3, and these may have a different pressure range. I would be interested to hear how these tires are working as they are on my short list for replacements.

[Dutch Star Don]

Chief Deputy....Since Newmar is one of the only companies that produces a 40' coach with a tag axle, the rear duals and tag don't individually carry a lot of weight. Consequently, you may find that your weights are at the low end of the tire chart and sometimes below their lowest setting. So there is a minimum that you need to use, often around 80 - 85 psi.

[enjoyrv]

I did a four corner weight yesterday and wanted to share the results. I hadn’t done it for a long time but with 8 new Michelin X Line Energy 315/80 R22.5 all the way around, I wanted to be sure I had the right psi and weight on each axle. Here’s the information:

2010 Dutch Aire 43’ with tag axle

Front axle rating: 16,000 lbs
Front right wheel: 7,300 lbs
Front left wheel: 7,600 lbs
Combined front axle: 14,900 lbs
* need to add 200 lbs driver and 150 lbs for passenger
Tire pressure set at: 115 psi

Drive axle rating: 20,000 lbs
Drive axle right: 7,450 lbs
Drive axle left: 6,950 lbs
Combined drive axle: 14,400 lbs
Tire pressure set at: 90 psi
* minimum is 85 but I didn’t want to drop below that number ever. We will be adding weight to rear closet.

Tag axle rating: 10,000 lbs
Tag axle right: 3950 lbs
Tag axle left: 3,950 lbs
Combined tag axle: 7,900 lbs
Tire pressure set at: 90 psi

Right side combined weight: 18,700 lbs
Left side combined weight: 18,500 lbs
Total weight of RV: 37,200 lbs.
GVWR: 46,000 lbs

Comments welcome.

[TJ]

Originally Posted by enjoyrv

Attachment 324518

I did a four corner weight yesterday and wanted to share the results. I hadn’t done it for a long time but with 8 new Michelin X Line Energy 315/80 R22.5 all the way around, I wanted to be sure I had the right psi and weight on each axle. Here’s the information:

2010 Dutch Aire 43’ with tag axle

Front axle rating: 16,000 lbs
Front right wheel: 7,300 lbs
Front left wheel: 7,600 lbs
Combined front axle: 14,900 lbs
* need to add 200 lbs driver and 150 lbs for passenger
Tire pressure set at: 115 psi

Drive axle rating: 20,000 lbs
Drive axle right: 7,450 lbs
Drive axle left: 6,950 lbs
Combined drive axle: 14,400 lbs
Tire pressure set at: 90 psi
* minimum is 85 but I didn’t want to drop below that number ever. We will be adding weight to rear closet.

Tag axle rating: 10,000 lbs
Tag axle right: 3950 lbs
Tag axle left: 3,950 lbs
Combined tag axle: 7,900 lbs
Tire pressure set at: 90 psi

Right side combined weight: 18,700 lbs
Left side combined weight: 18,500 lbs
Total weight of RV: 37,200 lbs.
GVWR: 46,000 lbs

Comments welcome.

Good data and congrats on a well-balanced coach! That’s how it should be done.

TJ