Tuesday, May 3, 2011


We had the great pleasure of having dinner with Dee and Jim (Tumbleweed blog) and it replenished our

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enthusiasm about Full-time RVing.

They make it seem so easy, even with the little glitches and gotchas. We discussed a lot of things about traveling, places they have liked staying and, of course, HDT tow vehicles and Smart cars.

Jim has been concerned about tire loads and is upgrading his wheels to 17.5 inch with an H load rating from the E rating on his current set of RV tires.  I am following this with great interest. I have long wanted a bigger margin between my tires and my max RV load.  Although I have a 21,000 GVWR on DaKotR spread across 3 – 7,000 lb. axles, the tires are the same as Jim’s with an E load rating of 3042 lbs. max/tire.

In my case, my pin weight accommodates about 4300lbs of the 21,000 lbs., leaving the axles, wheels and tires to handle 16,700 lbs., if I was fully loaded. The axles are clearly capable (21,000 lbs. total GAWR) and the 8k brake sets can handle 24,000 lbs. total, but the wheels/tires max out at 18,252 lbs. technically leaving me only a 1550 lb. margin at best.

The concerns I have  are more about “typical” in use loads rather than the “technical” specs.  Pulling a large 5th wheel means some curbs, road-edge runoffs, potholes and other things that will affect only 1 or two tires at a time. That makes it very easy to overload a tire or bruise a sidewall, weakening the tire’s actual safety.

I have lost 4 treads on older tires on this 5th wheel over the years and fortunately, no significant damage was done to the RV due to the King of the Road engineering of the tire wells and body of the RV. Flapping alligators don’t really have any compartments or body parts to contact.

However, even with a pressure pro or other TPMS to monitor tire pressures, I would only have immediately detected one out of the three failures because the others never lost pressure. When the treads stripped off nearly all of the weight they were carrying shifted onto the remaining two tires on that side.  Even brand new tires can be compromised for life by such overloading.

Good luck with this upgrade, Jim.

ttfn, Budd

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