Dear Dave,
I am going to downsize from a 35-foot Fleetwood Class A to a 26-foot Fleetwood Class A that does not have jacks. Do you think it is safe to use a leveling block under just the outside rear dual tire? The other option would be to use some type of wooden plank laid perpendicular to the tires. Thank you. I am a faithful reader. —Vincent, 2002 Fleetwood Southwind
Dear Vincent,
If you are going to use blocks for leveling, you should always use some that cover the entire tread surface of the tire as it sits on the ground. Since you will have duals in the back, that means wood under both tires running parallel with the tire tread or a piece large enough to cover the entire tread from side to side.
Several years ago I worked with the RV Safety & Education Foundation (RVSEF) developing a comprehensive owner training program, and one of the chapters featured tires. I learned way more about tires than I ever imagined. I thought I was already informed since I had worked in a full-service fuel station in high school and college, and even owned one for a few years. RVSEF spent years weighing coaches, collecting data on weights and tire pressure, and working with all the major tire manufacturers on how to reduce tire failure on the road.
Causes of tire failure
One profound statement made by all the tire manufactures is that oftentimes it is impossible to determine what exactly caused the tire failure as it could be a combination of issues due to lack of maintenance, weight, tire pressure, or stress applied to a tire over a long period of time.
Such is the case with blocking tires and using the proper size for the tire. You did not provide the year of the downsized Class A; however, I would assume it is on the Ford F-53 chassis with the smaller 16,000 lb. GVWR chassis. That chassis has 245/70R 19.5 tires that are typically 9.5” wide, which means you have 19” of tire alone and a couple inches between. Here is a chart from one of the leading tire manufacturers showing the correct and incorrect method of blocking tires.
Notice they recommend supporting both tires in a dual application. None of the diagrams shows the cross method for duals as this would take a rather large piece of wood and be hard to drive on. Most 19.5 tires have at least 16” of tread on the ground, so the wood would (wood squared?) need to be 16″ x 24”, at least 2” thick, and most likely you will need 2-3 pieces. Not easy to find a place to store, as most exterior compartments are only 22” deep.
Not good if entire tread not supported
What most tire manufacturers indicated is that not supporting the entire tread allows the tire and, more specifically, the rubber composition, to sit on a sharp edge and actually hang over that edge, which will weaken the components. As stated earlier, many tire failures can not be traced to a specific issue, but rather to stress applied over a period of time. And there is no actual data or proven research as there are several owners that have been blocking tires incorrectly for years and never had an issue like this one. Definitely not wide enough but adequate for the length.
What I like about this is that they had to add blocks to the front jacks, which would have raised the front wheels off the ground. So they added blocks under the wheels, so there may not be as much weight on the wheels if the jacks were not there. Here is a different situation that I would not recommend:
Bottom line, support the entire tread on the blocking whether you going North to South, or East to West. Plus, there are several blocking products on the market that are like Legos and are easy to store and assemble. I’ll let our readers chime in about those.
You might also enjoy this from Dave
What can I use to level my 5th wheel besides bulky wood blocks?
Dear Dave,
I have a fifth wheel trailer. It weighs 9,400 lbs. fully loaded. Is it safe to use plastic leveling blocks under the front landing gear? I’m trying to eliminate some weight by not using heavy wood blocks. Thank you, Dave. —Al
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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As a Tire Design Engineer I can tell you that Dave is correct about the necessity of supporting the entire tread of your tires when using blocks. For duals this means BOTH tires. Here are my blog posts on the topic.
https://www.rvtiresafety.net/search/label/Leveling%20blocks
I bought these rubber paving blocks from HomeDepot. They are large enough to cover both dual tires. https://www.homedepot.com/p/Envirotile-Reversible-16-in-x-16-in-x-0-75-in-Grey-Brick-Face-Flat-Profile-Rubber-Paver-MT5001608CM/302907057
Even with leveling jacks, you sometimes need additional height for uneven camp sites. I keep a pair of homemade 2 x 8 tiered wood ramps on each side of the coach. Reverse stacked on top of each other to save space. Better to have and not need than to need and not have available for use.
Hey Dave, on our first motor home, 99 Winnebago Adventure I had so many boards for leveling it almost took up a whole compartment! i used to use some 2 by lumber till I had one split, then I started using plywood that was much better & I could cut it to the width of my real duals! Actually found some T & G plywood flooring that was really good! After a couple of years of doing this I finally got hydraulic levelers! Now what to do with all that extra storage space?
Snoopy
Thank you, Dave! A few years ago we were in an unlevel campsite. Once our leveling jacks got us level, one of the tires was off the ground. DW urged me to slide one of our leveling blocks beneath the tire, which I did. Thankfully, we moved to a level site the following day. She’ll be pleased to know how right she was. 🙂
If you need to level a unit without jacks for some reason, either use cribbing that covers the tread width of any tire lifted. Bad things can happen if you don’t.
Maybe I like my coach’s frame and slides too much but I’d look for another site or move on before I need to stick 6 inches of cribbing under my tires like what’s needed with the two coaches pictured. Leveling jacks aren’t intended to lift tires, just stretch suspension…….