“Rubber components wear out, and a lot of the components that used to have grease zerks are now rubber, and those joints need to be inspected,” he says. “You can see wear there, or of course with a shock you can grab ahold of it and the rubber mount on it, and you can see whether it’s failed or not. Other places, like torque rods, you can see that the rubber ‘walked out.’ There are other places on the suspension where they’ve used rubber and you can easily tell from a visual inspection whether it needs to be replaced or not.
“I tell you, my guys go out all the time, and every time they go out, depending on what the complaint is, they carry a torque wrench,” Nash says. “A lot of the shops don’t have torque wrenches, and if they do, it’s been dropped so many times it’s not calibrated. And it’s so critical that fasteners on suspension brackets are torqued properly and in sequence. Or they don’t use the right fastener! A lot of times, these suspensions are Hucked, which personally, I prefer. But even the Huckbolts can be checked for torque.
“It’s clamp load that holds that suspension together,” he says.
Like Nash, Bruce Barton, director of engineering, Ridewell Suspensions, encounters horror stories in the field. One experience in particular points out why technicians need to use the right fastener, and use it properly.
“Upon a visit to a customer who was having some difficulties, we found that the nut on the pivot joint had apparently fallen off,” Barton says. “And, instead of replacing it with a like nut, they used a thread chaser. And it wasn’t torqued!
“That was really something to see,” he says. “It just illustrates the importance of making sure that the pivot joint is tight, and that the right hardware is being used.”
In Barton’s view, the pivot joint is the key component to an air-ride suspension. “On most trailer-type suspensions, there is one pivot point, and it’s important that that fastener be re-torqued early in the life of the vehicle,” he says. “Most suspension manufacturers would indicate a re-torque between 5,000 and 10,000 miles; that is often missed, and that is so key to the life of the pivot joint. When the vehicle is new there is some relaxation in that joint, and that first re-torque is critical to the robustness of that pivot joint.
“If that pivot joint is loose, it will more than likely destroy the hanger that is attached to the frame of the trailer,” Barton warns. “It has the potential to destroy and force the replacement of the bushing.”
As with the rest of the system, the manner in which it’s torqued is as important as whether it’s been torqued.
“A lot of times, mechanics will hit it with an impact wrench, as opposed to torquing it to the suspension OE recommendation,” Barton warns.
“The knowledge level of technicians isn’t where it should be,” says Randy Petresh, vice president-technical services for Haldex. “The biggest thing is that (suspension maintenance) is ignored. It’s an awareness thing that needs to be impressed upon the director of maintenance, who has to impress it on his technicians.”
Why does such an important system get ignored? “I think it’s this perception that the suspension systems are very robust, they take a lot of beating, a lot of abuse, and you don’t have to worry about them,” Petresh says.
Are you worried yet? Stay tuned: we’ll continue our air-ride suspension maintenance story next issue with a look at shock absorbers, air springs and ride height adjustment.