RV Confidential #11: Short Wheelbases and Accidents go hand in hand!
By : JD GallantJanuary 30, 2018
If the proof’s in the puddin’, then the proof’s in the photos!
I’ve been complaining about short wheelbases for so long that I’ve almost gotten to a point of acceptance that no one’s listening—so why talk too much? And, of course, for a consumer advocate that must never happen. But thanks to social media, I’ve been shaken wide awake by the terrific amount of photos of RV accidents being displayed. Luckily for me, many photos show the wheels so that I can readily estimate the wheelbase.
This motor home tells multiple stories. First, the wheelbase is so short that the risk of this happening was extremely high. Second, the wall structure completely failed. This motor home did not fall off a cliff—it was a rollover on relatively level ground. Third: if there was a cage around the cockpit, it must have been made of tissue-thin material. Since these issues are important, I’ll discuss sidewalls and cages more in an upcoming RV Confidential.
The other day I came face-to-face with a man who complained that I was too strict on the issue of short wheelbases. “I drive one and it never gives me a bit of trouble on the road,” he says. “Since I use it locally and park it a lot, I’m really glad that it has a short wheelbase. I wouldn’t have it any other way.”
Of course, being that I’m old and a squirt of a man, I didn’t argue with this young man who was half my age and twice as big. But I did lie awake that night and thought about the subject. Yeah, if you park a 50% wheelbase motor home a lot, life can be easier. But then, if you drive it even a little bit on the highway, the chance of life becoming a hell is too high to just pass it off.
It doesn’t take a mechanical genius to see that the overhang on this motor home is too long for road stability. Diesel pushers under 40 feet have a problem with increasing the wheelbases to satisfy RVCG safety ratings because the engine and transmission take up so much of the space at the end of the chassis there is no room for rear axles.
Unscrupulous RV salespeople (and I’ve met plenty of them) or ignorant RV salespeople (because they don’t know their products or don’t want to know their products) do not hesitate to push a trailer like this onto a person who has no real knowledge about towing. “Just hook on and go with it,” they are quick to say. “Yeah, if your vehicle can pull it, it’ll follow you anywhere.” Now, if you believe that, you are a risk to yourself, your passengers, and everyone else on the highway
Now in the photos I’m showing you, (all of which come from the internet) you’ll see that motor homes and travel trailers are not generally sturdily built. They simply don’t like to flip, hit a tree, or be crashed into. So, since they aren’t built for accidents, the best way to avoid an accident is to pick one and drive one like you don’t want to be involved in an accident. (As my grandson tells me, you need to drive a motor home like you’d ride a motorcycle.)
The real world tells us that most motor homes are heavy. They can weigh many tons. If you flip one on its roof, it’ll usually squash. Because I have been called by attorneys to inspect many motor homes that have been squashed and have come apart, I’ve accepted this structural weakness as a fact. Having been schooled in mechanics and the laws of nature called physics, it’s easy for me to picture the scenario of a short-wheelbase motor home being flipped over by the wind or other factors with specific results. As pictured in these photos, the results are often disastrous.
I have seen this scenario before. Towing a heavy vehicle behind a motor home can be very dangerous if the wheelbase is short (as this one appears to be) and the towed vehicle doesn’t have auxiliary brakes. In an upcoming RV Confidential, I’ll be writing about braking systems for towed vehicles.
To get the wheelbase-to-length ratio of a motor home, simply divide the wheelbase by the length of the vehicle. According to RVCG, under 51% is extremely dangerous; 51% to 54% is dangerous under many road condition and not adequate for general safety; 55% to 56% is marginal; 57% and over is usually steady on the road under most conditions. The higher the wheelbase-to-length ratio the safer it gets. (This subject will be coming up again when we discuss the relationship between tag axles and wheelbase.)
This motor home was one of the brands rated lowest by RVCG during the last thirty years. We’d find many parts of the interior barely holding together when brand new. When we checked used ones, even our volunteers and students rated them very low on durability. Of course, those driving and riding in this vehicle, didn’t know that.
Travel trailers aren’t as easy to tow as salesmen tell you they are. If you don’t hitch and balance them right, they’ll flip and take you and your towing vehicle with them. Fifth-wheel travel trailers are much more forgiving of low BOB (back-of-ball) ratios than conventional travel trailers (ball hitched). But even with fifth wheels, a low BOB ratio (called wheelbase by some manufacturers) can always be a problem on wet or slippery roads—as shown in the fifth-wheel accident photo. The statistics are clear: Almost all travel trailer accidents on America’s roadways are with conventional travel trailers; and most of those have low back-of ball ratios.
Ask any highway patrol officer and you’ll be told that accidents like this are commonplace. It is obvious that the back-of-ball ratio on this trailer is below the 70% that RVCG holds as the minimum safety limit. Although these folks had an adequate tow vehicle, once a trailer with wheels placed this far forward starts wobbling, it’s almost impossible to control—especially if it has a light hitch weight.
This low-profile telescoping trailer should have had its axles placed much farther back. Apparently, the manufacturer wanted to sell it to owners of small vehicles who thought they needed a light hitch weight. The combination of low BOB (back of ball) ratio and light hitch weight is deadly.
Caught on a dash cam, this frame taken from the video tells you how fast a wind-related accident (whether from truck or nature) can happen. I’m sure you can see that this trailer’s axle is in the wrong place.
This trailer’s axle placement appears to be close to the minimum; but since the tow vehicle seems to be adequate, one would need more details to conclude why this perfect rollover might have happened. I’m sure, however, that placing the axle back another foot would have made a great difference in road stability.
Can you imagine towing this long trailer with a small truck? Now study the axle placement and ask yourself what risk factor you’d attach to pulling this trailer down the road at 50 plus MPH with a one-half or three-quarter ton pickup truck.
This wasn’t just an accident. It was an accident waiting to happen. Anyone familiar with axle placement for safety will readily see that these axles should have been placed another two to four feet to the rear. As might have been done here, hitch weights should not be reduced by moving the axles forward because a combination of low hitch weights and short wheelbase (low BOB ratio) is what causes accidents. (This one is approximately 60% BOB ratio.) Even a heavier hitch weight with the axles placed as far forward as this one can have a sway (or yaw) under mild winds or truck bow waves. Trailers should have a Back of Ball ratio of at least 70%!
Fifth-wheel trailer accidents are not nearly as common as ball-hitched trailer accidents. This is because manufacturers typically don’t have to worry about keeping hitch weights low since fifth wheels will be pulled with a truck—which will normally handle the 20% to 25% hitch weights that are normally recommended for towing fifth wheel trailers. Your guess is as good as mine why this manufacturer placed the axles so far forward.
Now, I’m not trying to stop you from buying a motor home or travel trailer any more than stopping you from buying a new car. (Goodness knows, I’ve had too much fun in my motor homes and trailers.) I’m only asking you to choose an RV for safety more than the interior layout. By choosing right, you are assuring all concerned that you are doing your very best to return safely from another memorable adventure.
