Tri-axle bearings are placed under pressure on every turn. Similar to a wind-shear, the bottom of the wheel is often under a side force opposite to the top of the wheel. We have observed a wheel torqued out at the bottom or top by as much as 1-2 inches under a sharp turn. This is because the center wheel is the pivot point on the turn, while the front and rear wheels are literally dragged across the pavement. Even a modest turn under a heavy load will leave a tire skid mark on dry pavement an indication of the front or back tires dragging across the pavement. The shearing action caused by turns can loosen bearings and more importantly loosen seals allowing grease to leak out and away from the bearing.
Certain operating conditions should cause a truck owner to adjust their wheel bearing scheduled maintenance. Probably one of the biggest operating variables that could accelerate the need to tighten or repack wheel bearings is driver experience. All drivers make mistakes, but let’s face if you’re a new driver you’re going to hit more curbs and make more navigational mistakes than an experienced driver.
What do these mistakes have to do with your tri-axle wheel bearings? Every time a driver hits a curb a shock is absorbed by the wheel and a torque is shot directly into the wheel bearings, navigational mistakes mean more turning around, and more sharp turns. Each turn and curb hit shortens the life of wheel bearings and tires.
New drivers should be checking their wheel bearings daily for hot running temperatures and loosened fit. The right front wheel will be the first to loosen or get hot because it takes the first impact from a curb hit on a right turn. One hit to any wheel on a fully loaded trailer from a curb at even a very slow speed can torque a wheel enough to loosen the bearing or grease seals.
Each wheel bearing has an inside and outside seal. All drivers but in particular new drivers, should be on the lookout for signs of leaking grease. Black streaks on the outside of a wheel, is an indication the outer seal is leaking and grease. A broken inner seal is even more serious as grease can leak into the wheel drum and onto the brake pads significantly reducing the braking power of that wheel. Any black stains observed on the inside of a wheel should be given immediate attention after the trip.
Tri-axle trailers offer hotshot owners a significant weight advantage when running under a combined GVWR of 26,000 pounds, but they require a significant commitment to maintenance, and for new drivers… a daily vigil over their wheel bearing condition.