Rut tracking is the tendency of the vehicle to follow ruts in the road, causing the motorhome to shift and wander around as you drive over variations in the road surface.
As with other steering/handling problems, some coaches are more susceptible to rut tracking than others—especially those that are too light in the front. Short diesel pushers and coaches with a long rear overhang often exhibit rut tracking; more weight behind the rear axle makes the front end feel light, kind of like driving a truck with a load of gravel in the back. Our rule of thumb is that we want 50% of the weight carried by the rear axle to be over the front axle, except for the Workhorse W Series chassis, which typically wants 55%.
If your coach suffers from rut tracking, the first thing I would suggest is to have the coach weighed to check its weight distribution. If it is off by a few hundred pounds, you may be able to solve the problem by moving heavy stored items ahead of the rear axle, as close to the front as possible. Also, if you have a motorcycle lift on the back, you may want to consider having it relocated to the front, if possible. We had a customer in here recently that had a motorcycle lift on the back of his coach. Even without the bike in place, the coach was almost 2,000 lbs. too light on the front, and in my opinion, was already unsafe to drive. The dealership had told the customer that they would pay to have a steering stabilizer installed, but in this instance, it wouldn’t have helped; re-distributing the weight is the only solution in a situation such as this.
Some coach owners tow a trailer without even knowing what the tongue weight is. If you tow a heavy trailer with a car inside, for example, the tongue weight can be 2,000 lbs. or more—far exceeding coach’s rated tongue weight.
When a customer comes into our shop complaining of a rut tracking problem, the first thing we’ll do is conduct a Road Performance Assessment to determine the severity of the problem. We’ll take it in, check all the steering components, and weigh it at all four corners to determine the weight distribution. If it’s way off of our benchmark, we may add weight to the front of the coach to solve the problem. In some instances, we’ve added almost 1,000 lbs. to the front end. That’s a lot of steel, but it is still normally well below the front gross axle weight rating and tire ratings. We use steel plates, stacked together and bolted to the frame using hand-fabricated brackets. It may sound strange, but some coaches, especially short diesel pushers, actually come from the factory with weight bolted or welded on to the front end. When we fabricate weights for our customers, we make sure that the finished installation mimics a factory offering.
Tires are also critical. For example, Bridgestone 8R19.5 tires are wonderful for a delivery truck, but not for a motorhome application. These tires are narrow and have a stiff sidewall, which I feel makes them more prone to following ruts, and makes the coach ride a little harder, also. Bridgestone makes a variety of other tires that are better suited to the application. Goodyear and Michelin spend a lot of time developing tires for motorhomes, and they support the industry as well. Even so, it pays to do some research to determine the best tire for your coach, because once you’ve purchased them, you’re going to have to live with them for a while. Online forums, as well as other coach owners, are a good places to get some insight on the subject.
If your coach has a rut tracking problem, you may want to start by checking tire pressures, then experiment with pressure by 10 lbs. plus or minus; often, this can change the tracking characteristics. Get the coach weighed, and see if you can move some of the weight forward. If these suggestions don’t work, it may be time to consider the more serious corrective measures that I mentioned above. - Robert Henderson