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Mike8253 · 05-22-2025, 10:47 AM

I've always noted on my 34PA that inflation/temp growth on my PS rear duals while driving is consistently higher than all my other corners even though my travel weight margin for the rear axle is typically ~1600-1700 lbs. as compared to my rear GAWR. Thinking about it, it finally dawned on me that both the freshwater tank and propane tank reside on the PS, with the only comparable weight contributor on the DS being the Onan Generator @ 299 lbs. (not including supporting frame structure). While I know that my 70 gal. water tank can carry as much as 584 lbs. of water if full, I have no idea what the 24 gal. LPG tank (and support structure) weighs in total with its 80 lb. load of propane (19 gal.). The better I understand how those potential (fully loaded) weights compare, the better I'll be able manage their relationships when traveling to minimize their influence on the PS rear tires. Appreciate any insights you may have.

Galvanizd · 05-22-2025, 06:23 PM

My inside rear tires always run a bit warmer. I have tire monitors installed. I weighed my coach last year. All 4 "corners" . After that I moved my tool box from the passenger side to the drivers side. It made a slight difference. The inside tires still run warmer than others. I keep an eye on the tires but do not get too concerned.

We have dogs and my butt gets tired after about an hour and a half of driving, so we stop and things cool down while we walk the dogs. We also don't drive more than 250 miles now. No rush. Gives things time to cool down and my butt appreciates it.

bentjm · 05-23-2025, 06:31 AM

The only way to really know is a four corner weigh.

Mike8253 · 05-23-2025, 11:24 PM

Actually, I had forgotten that when I had the 4-corner LiquidSpring suspension installed, they did a before & after 4-cornner weighing. Following were the results after the install:

Front: DS - 4250lbs. / PS - 4280lbs. (9000lb. GAWR)
Rear: DS - 7280lbs. / PS - 7220lbs. (17500lb. GAWR)

Following conditions applied:
55 Gal. Gas
Full Propane
No Bikes
No Fresh/Waste Water
No Driver / Passenger(s)
No Bsmnt Cargo
No Main Floor Clothes/Food

So, essentially no (neutral) side-to-side weight bias (Unloaded).

The 70 gal. water tank sits just forward of the PS duals. Its basic cubic dimensions are 45.375"L/22"H/19"W, and in that location, its weight is biased ~82% to the rear vs. front axle, and nearly 100% to the PS tires. Full, it carries 584 lbs. of water.

Bottom line, the rear axle, at our travel weight, has plenty of capacity to carry the full water weight load if we choose to travel that way. We typically travel with the tank only around half full, though. But what I do have to work on now is to redistribute 300lbs (+ or -) of typical house/basement cargo from the PS to the DS somehow. At least by going thru this exercise, I understand, now, why the PS Duals are talking to me. And just for completeness, I take the CAT Scale axle weights and add 10% to the PSI called for in the tire charts as my SOP. We weighed the RV on the 1st day of our last trip of '24, fully loaded at the 1st Gas Stop after filling the tank (our max travel weight).

bentjm · 05-24-2025, 04:53 AM

So, when you weighed fully loaded at the CAT scales, how much weight was added on the front axle, and how much was added to the back?

Mike8253 · 05-24-2025, 08:03 AM

Attached is a .PDF Copy of the spreadsheet I use to document and track our travel weight in the Open Road. Visited the CAT Scale 2x last year. Interestingly, the axle weights were identical on both occasions. I use this spreadsheet to just plug in the CAT Scale axle weights, and it looks up the appropriate Tire PSI. I arbitrarily add 10% to the lookup value.

Note, also, on the 2nd attachment, that the weight increments from one PSI recommendation to the next are not consistent, so to comply with the "formal guidelines", you actually do need to do the lookup.

bentjm · 05-25-2025, 08:33 AM

It seems to me that you are overthinking this.

My 2022 40IP Allegro Bus was 400 lbs heavy on the passenger side front. I run about 17,000 lbs total on the front when fully loaded.

Barry at Josam said that difference was minor.

The guy that was doing 4 corner weights at the FMCA rally in GA said that anything less that 5% was good.

I did move my box of spares and my tools around some just because it was easy to do.

Mike8253 · 05-26-2025, 10:37 AM

Thanks for your replies. I neglected to include (unintentionally) in my original post that I pretty consistently get a PSI increase alarm on my TireMinder TPMS (annunciates at Factory Set 20% increase over the set baseline PSI) on the PS outer dual. (I installed new Toyo's last Spring. Had Michelins originally with no alarms.) One thing I realize from going thru this analysis is that with empty water / waste tanks, the RV is side-to-side weight neutral with full gas/propane tanks. So, I need to manage freshwater upload and side-to-side cargo loading to reasonably distribute the remaining weight add-on. And I need to get the PS outer dual checked out because it should not be generating an alarm given, I know that rear corner weight is within limits, and the inflation is proper for the weight being carried. I'll get the tire looked at this week.