Suspension Question
Q: I have a late 1990s type A chassis with a Chevy 454-cid engine. It has 46,000 miles on it and I’d like to make it ride better. I’ve made sure the front air bags don’t leak, but the wind causes it to lean too much, and it sometimes wanders on the road. The steering wheel begins to shake at around 50 mph and I have to slow down for curves. How can I tell whether the shock absorbers are bad? Can you help me?
Kevin Dornbush
Yuma, Arizona
A: In order to improve your coach’s ride, you may want to perform the following steps in the sequence outlined and test the coach’s ride after each step. You don’t want to just throw money at the problem, but rather approach it one step at a time.
Step 1: Checking to see whether the air bags are leaking is a good start, but you didn’t mention whether they are inflated to their rated pressure, which is at least 60 psi. According to a representative at Workhorse, the current manufacturer of the P-Series chassis, air bags rarely fail but could be pinched and damaged if they are allowed to operate empty or under-inflated.
Step 2: You need to weigh your motorhome. Before weighing it you should load it as you would when going on a trip. You can weigh the axles separately but at the same time at a Cat Scale, which usually can be found at large truck stops. The scale operator will give you a printout that includes the weights for both axles individually as well as the total weight of the coach. While it would be better to weigh each wheel separately, this is about as good as you can get without going to an FMCA international convention or area rally and having representatives from the Recreation Vehicle Safety Education Foundation do the job.
Step 3: You also need to check your tire pressures before proceeding. Check the tires while cold, which is considered the temperature of the tire “” and the air inside “” after the tires have not been driven for a certain period and have cooled to a stable temperature regardless of the ambient temperature. Just make sure you check the pressure before moving the coach and you’ll be fine. You should not operate the coach on tires that are inflated below the recommended pressure listed on the vehicle’s certification label affixed near your driver’s position.
Step 4: If your steering wheel begins to shake at around 50 mph, your tire balance may be off. Either have a set of wheel balancers, such as Balance Masters, installed or have your tires rebalanced at a service facility that is accustomed to working on motorhome or truck tires. The tires need to be dynamically balanced (high-speed spin balance) without using more than 14 ounces of weight per tire/wheel combination. If more than 14 ounces are needed, the tire needs to be “reclocked” on the wheel (rotated at least 90 degrees on the wheel) and rebalanced.
Step 5: After making sure that the coach’s air bag pressures, weight, tire pressures, and tire balance are all correct, you can address the remaining suspension components. Unfortunately, you can’t test the shock absorbers on a motorhome like you can on a car (push down hard on one end and release quickly. If the car rebounds and stops bouncing, the shocks are still good. If it keeps bouncing, they need to be replaced). On a motorhome the shocks need to be inspected carefully for leaks around the shafts or below the reservoirs. If the shafts have more than a very, very light coating of fluid on them or if you observe any fluid residue below the shocks, they should be replaced. If one faulty shock is found, my recommendation is to change them all. If you don’t see visible leaks in the other shocks and are hesitant to replace them all, at least have an expert technician inspect the “good” shocks for leaks or other possible problems.
Step 6: After performing steps 1 through 5, if your coach still leans uncomfortably in cross winds or on curves, you may want to consider upgrading your antisway bars “” also known as sway bars. Suspension technology has improved considerably since your chassis was manufactured. When your chassis was produced, the common practice for manufacturers was to use the size-to-weight ratio used in automobiles and pickups (bar diameter to car weight ratio). Since then, however, the ipd Company has discovered that larger, heavier-duty bars can and should be installed on coaches (possibly due to the coach’s higher profile), so ipd now offers a 1-5/8-inch front bar (3/8-inch thicker) for the older P-30 chassis. Therefore, ipd should be consulted as to what the company can offer for your coach at this time. I’m sure the difference in the ride will amaze and delight you.
Step 7: After testing the shocks and the antisway bars, if you still feel you need more assistance, consider a system such as the Steer Safe steering stabilizer. This will aid you in controlling the wheel when the coach hits ruts or cracks in the roadway, when you’re driving in windy conditions, etc.
I have one final suggestion. You may be guilty of “over-correcting” while driving. Like a small airplane that could fly itself better than a nervous novice pilot, a motorhome driver may be “chasing” the control without ever “catching” it. What I mean is that you may be moving the steering wheel needlessly as the coach tends to follow the wind or the road. Next time you find the coach wandering back and forth, hold the wheel steady and see whether it doesn’t straighten itself out. When you do need to make a correction, move the wheel slowly to center the coach in its lane. If the motorhome continues to move around more than you’d like, have a technician inspect the mechanical parts of the steering system (steering gearbox, steering shaft connections, tie-rod ends, etc.) to see whether any of these components may be faulty.