RV Tire Safety: Two front tire “blowouts” in one day

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with RV tire expert Roger Marble

There was a thread on a forum started by the owner of a Class A motorhome who suffered two front-end “blowouts” on the same day. There was not a lot of data provided such as actual load on each front tire or the tire age, or even when the last tire inspection was completed. But here is one of the replies in the thread:


“The reason that your coach is equipped with a heavier axle and bigger tires is exactly that the axle and tires on the earlier model Aspires were too close to what the coach was carrying. The close limits on the Aspire as well as the tire choice on OEM tires have been a well-known concern for years and many Aspire owners that frequent this forum have shifted their tires to tires with higher weight tolerances and inflation load-carrying specs and overall better safety record.

“My 15 Anthem was similar. With me fully loaded for travel (which was still well below the coach’s maximum rated weight) and tanks all loaded and us sitting in our seats, I was also overloaded on my front axle by 140# which was deemed acceptable. It was that way the whole time we owned her. A whole lot of weight is borne by these front axles on coaches this big and heavy … within tolerances and specs, but close. —Gary

I can’t address the accuracy of Gary’s comments on the Aspire or Anthem motorhomes but I have heard of other cases where the OE tires, and even the front axle in one case, were in overload when the RV was shipped from the manufacturer.

Individual tires don’t care about the load on the other tires on a coach or the average load on all the tires – only on the load on that individual tire. This is why “four corner weights” are strongly recommended for all RVs.

GAWR (gross axle weight rating), not GVWR (gross vehicle weight rating), is what is important for each axle, BUT that is assuming a perfect 50/50% side-to-side split in load – which is almost never the case. Some coaches have been found to be unbalanced by 500 pounds to over 1,000 pounds yet still close to GAWR.

Also, having a reasonable “reserve load” is very desirable, especially in the more critical front position. A reserve load (tire capacity minus the measured load on that tire) of at least 5%, with 15% being a good goal, may require changing the amount of “stuff” you carry, or moving “stuff” around, or even getting higher-rated tires.

You can also stagger tire replacement if you have the same size tires in all positions. I cover how to do that in my post on spreading out the replacement cycle. My post has a 1-year cycle but you could easily change that to 2 years and never have tires over two years old on the front axle.

 

Read more from Roger Marble on his blog at RVtiresafety.net.

 ##RVT915

 

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Jrw

A friend asked me to check out a class A he was considering. It was 35’ or 37’. The weight as shipped was just 900# less than the gvwr. He, wife, and dog took about 375# of that. Add some clothing, food, and required stuff and surely over gvwr