KANAKASKIS, Alta. – Spec’ing for trailer suspensions can be a bumpy ride if some factors get overlooked. Ultimately the end-user’s application of the trailer should be the deciding factor, but with a wide variety of options it requires informed decisions.
“You tend to get a noisy lining when you over-spec’ components,” explained Randy Billian, engineer with Dana Canada, axle plant. “All told there are about 174,000 variations we have to manage. You have to use components as intended because you can’t fool steel.”
Billian was part of a panel discussing suspension issues at the Canadian Transportation Equipment Association’s 43rd manufacturer’s conference in Kananaskis, Alta. Oct. 23-25.
“To properly spec’ a suspension the end-user has to look at the application, it all comes down to education,” said Alain Lamothe, technical service manager with Hendrickson Canada. “It is vital to look at the operating conditions when selecting a suspension and not only at the axle loads.”
The three different suspension types are spring, rubber and air-ride.
“Rubber and spring have a fixed spring rate and no load equalization,” noted Lamothe. “Air-ride has an adjustable air bladder, so you can equalize your axles and lift them.”
As well, each suspension can be configured either in a top-mount position, an underslung position or as an integrated system.
“If you can take all your components and integrate them together you will typically have a better product,” commented Lamothe.
To get the most out of your suspension it is important to watch the use of fasteners. Some common problems Lamothe sees are re-using fasteners, contaminated fasteners and using different fasteners than the originals.
“Clamp load is important. If you change your fasteners or coatings, it throws the clamp out the window,” he explained.
Bent sliders can also become a problem if the pins are not in place when the driver brakes. Proper training is one way to combat this issue, but there are also products that can offer additional insurance.
“With angled locking pins the slider will hit the first hole when the pull handle is released,” said Jeff Davis, director of OEM sales and trailer products with ArvinMeritor. “Angled pins with air assist pin mechanism eliminates slider bending due to driver error.”
The interaction between a trailer’s suspension and its braking system also requires due attention.
“The standard spring brake requires more room for installation. The stroke requirement is reduced when using the self-steering axle or any axle with shorter cams,” said Jules Guillemette, vice-president of engineering with Fuwa USA. “With the forward or front-lift, if an air brake is required it will start encroaching on the air bag.”
With the addition of new parts to a suspension system, it should not always be assumed that the old measurements will suffice, especially when dealing with self-steering axles.
“You cannot take the same measurements you have always been doing with self-steering axles; make sure the proper measurements are made,” explained Guillemette. “Please consult the manufacturer before you modify any part of the suspension or the axles. Installers should always explore alternatives and talk to suppliers.”
Another common problem the manufacturers tend to see among end-users is adjusting the ride height, which can cause significant problems.
“Don’t mess with your ride-height. When you see people tinker with it, it goes away from what it was intended,” said Davis.
“Sometimes when a driver leaves the yard with a stock trailer, they try and make it better and that’s when you get into problems,” added Lamothe.
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