February 2013, TruckingInfo.com - Feature
The continued demand to reduce costs associated with tires has led suppliers to introduce axles and suspensions to address this need.
For instance, the SAF CBX Self Steering axle suspension addresses tire wear from tire scrub.
Widespread and multi-axle trailers “scrub” the tires laterally on the road surface for every turn the vehicle makes. The higher the loading on the tire, the greater the scrub on the tire, axle, suspension and trailer frame during turns.
The self-steering axle suspension allows the tires to follow the turn of the vehicle as opposed to being pulled laterally through a corner. Thus, when loaded, the SSA carries its share of the designed capacity of the trailer and virtually eliminates tire-scrubbing issues.
The relation between axles, suspensions and tires also becomes a fuel economy issue.
Hendrickson says its SteerTek NXT fabricated axles help maintain better dynamic toe and camber alignment compared to forged I-beam axles, contributing to optimized tire performance. Tires that operate more efficiently decrease the amount of rolling resistance, which contributes to better fuel economy.
Proper inflation is also key to fuel economy as well as tire life, and there is increased use of tire pressure monitoring and inflation systems.
One such product, on the market since 1993, is the Meritor Tire Inflation System by PSI. MTIS goes onto an estimated 36% of all new trailers in the U.S. today, according to Frank Sonzala, PSI executive vice president.
Success comes from results, Sonzala says. A controlled two-year test of the product on trailers showed a 1.4% increase in fuel economy, and there are other benefits.
Sonzala says the apparent cost saving in tires, fuel and the elimination of road service calls means a less-than-eight-month return on investment for many fleets. One is Werner Enterprises, which is retrofitting 24,000 of its trailers at 10 depots nationwide.
Hendrickson, however, says there is a drawback to the typical tire inflation system. It says its TireMaax Pro addresses the problem of tires that are over-inflated or, in the case of duals, mismatched, says Matt Wilson, business unit director for the Controls Business Unit of Hendrickson Trailer Commercial Vehicle Systems.
“A typical tire inflation system cannot actively control the pressure of a tire once it has exceeded the system target pressure,” Wilson contends. Tires that are above the target pressure will not trigger any response from typical tire inflation systems, he says.
“Because tire inflation systems constantly fill tires with air at ambient temperature, over time it is likely that these systems will fill tires with cold dense air. So the inflation system is actually a contributor to tires that are above the target pressure once the outside temperature warms up.”
TireMaax Pro uses special valves in the hubcap and a sophisticated controller to equalize the pressure across all wheel positions and relieve pressure from any over-inflated tires.
MTIS so far has been limited to trailer-axle tires, but engineers are developing an inflation system for drive-axle tires, says PSI's Sonzala. This is more difficult because the more complex drive axles must be made or modified to take internal air lines.