In “Minimize Resistance, Maximize Fuel Economy, Part II” post, we discussed the importance of checking your trailer’s alignment. We recently had a customer come in who took this advice to heart, and decided to have his double-axle fifth wheel trailer checked out. Indeed, it was out of alignment, but that was only a small part of the story.
Because the owner towed the trailer with an F-350 4WD, he had had the axles flipped previously, and during the process, the technicians had apparently neglected to re-install the shocks. I say “apparently” because there were upper shock mounts on the frame, but not on the leaf spring perches, which leads me to believe the trailer had shocks at one time.
This trailer is comparatively high-mileage-it sees about 15,000 miles a year. All those miles near maximum load capacity without shocks had taken a toll on the trailer. The shackle mounts and hardware showed serious signs of wear; the serrations on the bolts were almost worn off, and the mounting holes were egg-shaped (see photo).
Even more of a concern was that the steel wheels showed signs of serious cracking (see photo). The last time the owner had the tires replaced, he elected to use a heavier-rated tire. There’s nothing wrong with that, except that a heavier rated tire can take more inflation pressure, so you should always make sure that your rims can handle it. Exceeding the rim’s recommended pressure can cause damage and outright failure.
To solve these issues, as well as make for a safer, better handling trailer, we installed new shackle hardware and replaced the cheap plastic bushings with greaseable bronze bushings. While the suspension was apart, we also installed a Trailair Center Point air suspension, which simply bolts in place where the original spring equalizer used to be. In my opinion, this Trailair system is one of the most cost-effective air suspension systems you can have installed. It improves the handling, cornering, even the braking, because the air suspension does a better job of keeping the tires on the pavement. We added a fill valve and a pressure gauge to the side of the coach so it is easy to monitor the pressure in the bags (see photo). You could also add an on-board compressor to keep them inflated, if desired. We then bolted new shock mounts the spring perches, and installed new shock absorbers. Finally, we installed a Fifth Airborne air hitch, which further reduces ride harshness and “chucking”.
The tires were fairly new and in relatively good condition, but obviously, the rims required replacement. As I have mentioned before, I’m a big fan of reducing unsprung weight and rotational mass. The heavier a part is, the harder it is to make it change direction, and that has a negative affect on the ride/handling of any vehicle. So instead of using steel wheels again, we went with Alcoa one-piece forged aluminum wheels, which are several pounds lighter than the stock wheels. They not only look a lot better, but these forged aluminum wheels are much stronger. Note that I stressed “forged”. There are a lot of inexpensive cast aluminum wheels on the market, but they are nowhere near as strong.
When the trailer was put back together, we inflated the Trailair bags and let them sit overnight. I always recommend letting a new air suspension sit overnight before you hit the road, just in case there are any leaks. In our case, one of the push lock connectors had a tiny leak in it, and it lost several pounds of pressure overnight. Because air bags contain such a small volume of air, a small leak can empty the bag in no time.
After the small leak was fixed, we aligned the trailer off of the king pin, so everything is set in reference to that. Now the trailer tows straighter and cleaner with reduced aerodynamic drag and improved tire life.
We also made several improvements to the tow vehicle, but we’ll talk about that on the next post. See you then!