Sightseeing while driving is something we all enjoy, but when your motorhome wanders, it can take the fun out of your journey. You know, you just look away for one second, and your motorhome is on its way out of the lane—it requires constant attention to keep it going in a straight line.
We call this issue “road wander”. The John Deere chassis was notorious for it—we used to call it “the wandering Deere”, but that’s another story. You may recall the column I did a few months back on steering freeplay; wander has similar causes. Between the steering wheel and the front wheels there are a lot of components—couplings, steering gear, sector shaft, pitman arm, drag link, bell crank tie rod ends, etc. If there is too much play in one or more of these components, the front wheels can have a mind of their own. To diagnose road wander, we first take the coach on a Road Performance Assessment to see how it behaves. If we can rule out “tail wagging the dog” (another condition I've written about) as a handling problem, then we focus on the front of the coach. For road wander, we’ll pick a nice, straight flat section of highway and hold the wheel straight; if the coach changes direction on its own, we know that wander is the concern.
Diagnosing the cause is done systematically by putting the coach on a lift and checking every single component that contributes to the steering. One of the first things we’ll look at is the steering gear box; motorhomes use what is called a reciprocating ball type, and they usually have a certain amount of play in them by nature of their design. Next, we’ll look at the steering linkage that attaches to the steering gear box, which is called the “pitman arm.” Some pitman arms have joints that can be replaced if they wear out—but sometimes, the joint simply wasn’t tightened down properly at the factory and came loose. The “sector shaft” comes out of the steering box and has splines on it; if the nut wasn’t tightened down properly, there could be play in the splines, and the shaft may also have been damaged in an accident of some kind.
With some steering systems, the steering linkage is supported by a mechanism such as an “idler arm” or “bell crank”. One of the things our manufacturing division, SuperSteer, is known for are the bell cranks we make to support the linkage on the P32 chassis and the Freightliner XC chassis with a straight axle.
On chassis such as the Ford F53, Workhorse and FRED, which have leaf springs on the front, steering wander can also be caused by front axle walk (axle moving from side to side). In these instances, the problem can be rectified by a front trac bar. We carry a Roadmaster product for these applications, but we have been known to build a custom Trac Bar for some of those old John Deere and Osh Kosh chassis as well.
In some instances, the motorhome may have a lot of rear overhang, which makes the coach light on the front axle—especially if the coach has a short wheelbase. The solution here is to add weight to the front axle (while remaining well within the front GAWR) to make the vehicle track properly.
Another consideration for road wander is the tires, and you should pay particular attention if you’ve just replaced them. We had an experience on our work truck that we travel to shows in; we replaced the tires with a different brand than we normally use (the store we stopped at on the road didn’t have any of our brand/size in stock), and the van seemed like it was all over the road. It was so bad, in fact, that we stopped at another dealer as soon as we could to exchange the tires for our usual brand. A tire that is narrow, such as an 8R19.5 can get into ruts, while different tread patterns and sidewall construction can also be contributing factors.
With a little knowledge in hand, hopefully you’ll no longer wonder what causes wander.
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