2012 DSDP Weights and Tire Pressures

[MJFZ]

I have a 2012 DSDP 3734, this past week I went to my local ( and selling) Newmar dealer, Beckley’s RV in Thurmont, MD to have the entry door adjusted and while there, I had the coach weighed. Weight’s taken with full fuel, Driver, ¼ tank fresh water, empty black and gray tanks, well packed (less clothes and food). Typical travel weight would increase this by passenger(s), clothes, and food, everything else we carry is in the “As Weighed” weight. When we travel we always leave with empty gray, and 3 gallons in the black tanks and only haul ¼ tank of fresh water.

As weighed
Left Rear: 9000 Left Front: 6600
Right Rear: 9400 Right Front: 5500

Planed Travel weight:
Left Rear: 9000-9500 Left Front: 6600-6800
Right Rear: 9500- 9800 Right Front : 5700-6000

Per the chart for 305/70R22.5 LRL XRV, at Michelin North America RV Load & Inflation Tables (sorry, I could not figure out how to cut the chart out and paste it here in a readable format) I am planning to run the fronts at 100 psi and the rear at 80 psi ( measured cold). The coach was delivered with 120 psi in all six tires and I initially dropped all of them to 110 psi before I had the coach weighed. Though the chart says to run the rear dual’s at 80psi this just seems low. Any feedback on my plan?

Mike

[Route 66]

You can safely rely on the Michelin tables.

I ran 110 in the front and 85 in the rear per the Michelin tables for the weights I had.

Remember that there a 4 tires in the rear to carry the weight, so they don't need as much pressure as the 2 fronts.

It would be a good idea to get the 4 corner weights with the MH fully loaded to determine the actual pressures needed.

[Brigadoon]

I'm curious, do you have any idea why there is an 1100 pound difference from side to side on the front?

[Beacher]

At one point I had the same tire size and your weight is about 3% less then my was. I put 110 in the fronts and a little more helps because of steering in the rears I ran 95 and know problems had about 20,000 miles on the coach. To me 85 is not much I'd worry about the bead coming loose just my opinion.

[Beacher]

Sorry I meant to say the owner Craig Beckley and I camp together. Beckley Camping Center is the greatest they take great care of the costumer.

[FlyingDiver]

Originally Posted by Beacher

At one point I had the same tire size and your weight is about 3% less then my was. I put 110 in the fronts and a little more helps because of steering in the rears I ran 95 and know problems had about 20,000 miles on the coach. To me 85 is not much I'd worry about the bead coming loose just my opinion.

Since the Michelin tables for that tire go all the way down to 75 lbs, I really don't see how running 80 or 85 can be considered a problem.

joe

[Beacher]

When I talked to my Michelin dealer he said that low of pressure didn't sound right and told me about the bead maybe braking loose. We just got our new 2012 DSDP and when we picked it up from the factory it to had 120 in all the tires I weight it and then set the tire psi. I put 110 in the front and 100 in the back also in the tag didn't like the ride so I dropped the rears to 95 the ride is great and I'm still in the guide lines of the psi.

[MJFZ]

Originally Posted by Brigadoon

I'm curious, do you have any idea why there is an 1100 pound difference from side to side on the front?

Hi Brigadoon.
When we weighed the unit, the technician and I discussed what probably is creating the difference. The Drivers side has a larger slide out than does the Passengers side. I also have the six 6V batteries on the drivers side just aft of the front tire and the LP tank just aft of the batteries. Most of the additional weight we would add for any trip would be place on the Passengers side including refrigerated food and passenger(s).

Mike

[GaryKD]

Hi MJFZ,
The last time I talked with Michelin (about 3 years ago) 85 PSI was the lowest they like to see in the rear tires. Things change, over time, consider calling Michelin and verifying the 80 PSI. If they verify the 80 is correct, go with it and sleep well at night.

[MJFZ]

Originally Posted by Beacher

Sorry I meant to say the owner Craig Beckley and I camp together. Beckley Camping Center is the greatest they take great care of the costumer.

Hi Beacher.
I have never had the pleasure to meet Craig Beckley. Please let him know we have been very pleased both with the purchase and service from Beckley's. The sales department was very patient with my wife and I during our two day PDI. when I was in last week, I was very impressed that the service manager saw the technician weighing the coach and he took time to verify and then review the weights and check our weights against placarded weights and then discussed my weights with me.

Happy to see they are expanding the lot around the Service Department-- it was getting tight.

Mike

[Beacher]

Craig takes a lot of proud in making sure everything goes great and his people know about what their working on. I've know Craig for about 13 years and I was the first costumer that him and his family went camping with. I remember his wife saying are you sure about this lol well 13 years later were still camping. Your right about being out of room when he finished the new service center he was already out of space what he add will help. The next time your up there or call and ask for Craig tell him how everything went good or bad he likes to hear both he's always trying to make things better. Good luck with your new coach have fun and be safe.

[Wayne M]

We have posted before on the good service we received from Beckley.

Thanks again Beckley.

[Wayne M]

Here's the chart for your tire:

[Wayne M]

Using the "as weighed" loads you have to use the heaviest tire weight for all tires on the same axle.

Let's take the front tire first @ 6600 pounds (x2 = 13200 axle weight)

According to the chart, the minimum inflation for the weight of 6600 pounds is 100 psi. That would be for a load of 6770 pounds and only allows for 170 pounds of "fudge factor." You cannot stop at McDonalds and eat hamburgers every day or you may exceed that 170 pound. Also, don't stop and buy ice, groceries, and don't take the "partner" with you. (well that is per tires so it is a fudge factor of 340 pounds, but then, I have not met your family. Hee hee!)

The next up in the chart is 7040 @ 105 psi. Now that is more like it. The fudge factor is 440 pounds (x2 tires - 880 pounds) of fudge factor. That is a very comfortable margin.

Considering all things being equal, even if you change climates of 30 degrees (2% change for each 10 degrees of temperature change (increase temperature - increases pressure)), and a 5000 foot change in elevation (0.48 psi for each 1000 feet (Increase in altitude - increases pressure)), you will still be within the manufacturer's recommended pressures for load weight.

Looking at the rear, the "as weighed" pressure would have to be calculated using the higher 9400 pounds (x2 = 18800 pounds) (All tires on the same axle must use the same PSI)

So, for duals, 9400 pounds would have to have the minimum the mfg recommends of 75 psi. That is for a load range of 9530 pounds. The unfortunate thing about setting to that rate is that you have to maintain that pressure for decreases in temperature and altitude and you could be constantly adding air if it falls below 75 psi. You would not have to worry if it increased to 80 or above as it would still fall within the max allowed by the manufacturer. At 9400 lbs, 75 psi you are 130 pounds under the allowed for 75 psi.

You say you want to run the rears at 80 psi and that will support a loaded tire of 10030 pounds. Even at your planned loaded weight you will be well within the recommend inflation by the manufacture's chart. Personally I would run 85 and not have to worry about temperature and altitude drops of 5 or more pounds.

I'll leave figuring the fudge factor for the rear and other planned weights to a better mathematician. All I know is that if 2 plus 2 equals 5, then 2 plus 2 equals 4.

Happy trails.