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Saturday, October 24, 2009

Smoother with Air

I’ve read your article on steering and handling, and am hopeful I can extract a more customized opinion of what direction I should take with our motorhome. We have a Thor 27-foot Class A machine on a P37 chassis. It now has 56,000 miles on it. We installed Bilstein shocks on all four wheels and replaced the original steering dampener so although the steering is not as nice as our cars, it is acceptable. I would like to take smaller back roads when we travel but the roads are not as smooth of course, and last week we rattled our teeth out on a bumpy road. How to make the small bumps smoother (more comfortable) is my question. I’ve seen a few different things advertised; air bags, extra springs, etc., but cannot figure out the degree that they will affect the performance. Most items seem more directed at directional control, which is nice, but I want smoother bumps. What would you do, short of buying a better unit?
Rob, (New Bedford, MA)

Rob, I have been a big fan of the Firestone air bag system with independent air filler hoses ever since they came into the market. Adding leaves to the hard springs will help some, but remember you are adding steel to steel. It will effectively raise the rig and it may provide a touch more smoothness to the ride due to the weight shift, but by and large, the ride will still be “stiff.” A stiff ride that hits a moderate bump will amplify the “bounce” that occurs after the bump. The added spring dimension may lessen the distance of the resulting bump (the overall upward and downward movement), but the bump will still be there. Riding on two cushions of air at the rear axle will absorb more shock and not only lessen the up and down distance, it will better control that first abrupt hit the motorhome takes. It will be smoother with air bags. This will also raise the rear accordingly, throwing more chassis weight to the front axel, thereby, improving steering and handling. Independent air inlets will allow you to vary the air pressure in the bags. 

No coach is built symmetrically and perfectly balanced so, invariably one side will need to be lifted more than the other. You’ve done well to install the Bilsteins and the steering dampener, but the addition of air bags will probably yield better results for smoothing the ride. Slower speeds will also improve handling and ride-ability. But don’t expect perfection; it’ll never happen. At best, these add-ons will minimize the dynamics of a big box bouncing along the highway.


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