Air Bags?

Buster52 wrote:
Tatest, So you are saying that the P-30 chassis that was not really designed to be used for the weight of a RV. That the air bags is just a Rude Goldberg thing. Right?

Original market for P-30 was panel vans at GVWRs up to 12,300, with 13,500-14,000 a early stretch, which included the air bags. In the motorhome market P-30 got pushed to 16,000 and 18,000 with axle and spring changes for the rear, air bags inside the springs up front at higher pressures. Eventually replaced by Workhorse W16 and W18 chassis with leaf springs and solid axles up front, and heavier frame rails, more modern brakes, etc.

Chassis manufacturers could easily put heavier springs on their motor home chassis, however you wouldn't want to ride in a rock. Such heavy springs could also affect the relatively weak frames of a motor home.

Owners expect so much from their vehicles, and suspensions are all just one big compromise. They want chassis' to handle the weight of their coaches, while riding soft. And they want them to handle reasonably well--and stop when they hit the brakes. Air Ride suspensions are a good way to meet these goals for a reasonable price.

The chassis manufacturer has no control over the amount of weight that the coach manufacturer will put on the front suspension or the distribution from side to side. The bags are typically inflated to 70 psi but in reality you should adjust the air pressure to level the front end "front to rear" and "side to side". A yardstick is your friend!

To make use of stronger springs the manufacturer would also have to use higher rated axles, tires etc...all adding to the bottom line. Vehicles are built for the "average" user considering function and ability while still satisfying comfort and profit.

The bags if Firestone brand are lifetime warrantied if that is any consolation.

You have to consider the ride as a factor. The stiffer (stronger) the springs, the harsher the ride.

Ah. You see, its all about appearance and perception!!!

When someone see's an RV or pickup truck sagging at the rear, they assume its overloaded and struggling. If level, its assumed safe, within limits, and handling the load easily.

Do you get my point?

Tatest, So you are saying that the P-30 chassis that was not really designed to be used for the weight of a RV. That the air bags is just a Rude Goldberg thing. Right?

Which RVs are you talking about?

The GM P30 series chassis (for a while sold as a Workhorse) used supplemental air springs up front, it seems that GM didn't have springs heavy enough for some of the RV applications, and weren't selling enough chassis into that market (most P-chassis were used to build lighter commercial vans) to develop a different solution. That doesn't make the chassis obsolete, as the air springs are easy to replace when they wear out. What made the P-chassis obsolete was development of better chassis in that weight range.

Nobody else is building a chassis using supplemental air springs currently. Most heavy rear-engine chassis have air springs as the main springs, lighter chassis have metal springs, leaves in the rear and leaves or coils upfront.

For those with metal springs, chassis capacities range from about 9000 pounds to 24,000 pounds, springs and other components sized to the design load. If the RV manufacturer uses the right size chassis, supplemental springs are not needed. Some manufacturers install rear supplemental springs to help level the ride when the RV is close to maximum load for the chassis, but nobody is using them to increase load capacity, the way GM did for the P-series.