Truck Wheel Bearings Dammam

Two designs, one job: tapered pairs and hub units

Traditional wheel ends use two tapered roller bearings, an inner and an outer, running on the axle stub inside the hub, with the preload set by the axle nut. Newer axles use a single pre-set hub unit that is replaced complete. Tapered roller bearing designations begin with series numbers such as 30, 32 or 33 and are stamped on the race.

Each tapered bearing consists of a cone with its rollers and a cup, the outer race pressed into the hub, and the two wear together. Keep every cone with its own cup, and never mix parts from different makers in one pair.

Warning signs that a wheel bearing is failing

• A low rumble or growl that changes when the truck leans through a bend.
• One hub that runs noticeably hotter than the others after a run. Check with an infrared thermometer rather than your hand.
• Grease or oil leaking around the hub cap or onto the brake back plate.
• Play in the wheel when it is rocked top and bottom with the axle safely raised.
• Uneven tyre wear, or a wheel that wobbles at speed.
• Smoke or a burning smell from a hub, which means stop at once.

Replacing a wheel bearing set: the sequence that lasts

1. Identify both bearings and their races from the numbers on the old parts, and order the seal, the lock washer or nut and the grease with them.
2. Remove the old bearings and races, then inspect the axle stub and the hub bore for wear, scoring and a spun race.
3. Clean the hub, the stub and the brake area, and keep grease away from the brake linings and drums.
4. Fit the new races square using the correct driver, and pack the new bearings with the specified grease.
5. Fit the new seal without damaging its lip and check that it seats at the correct depth.
6. Set the preload and end float to the manufacturer's procedure, lock the nut and fit the hub cap.
7. Spin the wheel by hand, listen and feel for roughness, and check again after a short loaded run.

Preload: the setting that makes or breaks a bearing

A tapered roller bearing must run with a small, controlled preload or end float, set by the axle nut. Too loose, and the rollers skew, the wheel wobbles and wear starts at the edges of the races. Too tight, and the bearing runs hot, the grease breaks down and failure follows within a short distance.

The procedure is set by the manufacturer and typically involves tightening to a specified torque while the hub is turned to seat the bearings, backing off and re-tightening to a lower figure, then checking the end float with a dial gauge. Do not set preload by feel, and never reuse a nut or washer that no longer locks.

Why replacing only one bearing is a false economy

Bearings and races wear together, and a new bearing running in a worn race will not last. Replace the pair, both races and the seal on that hub. If the failure was caused by contamination, check the wheel-end seals on the rest of the axle, and look at the other side too if the parts are the same age. The extra parts cost little compared with a second breakdown and a second wheel-off.

Sand, salt and water: what wears wheel ends in the Eastern Province

Seals keep grease in and dirt out, and airborne dust erodes their lips. Heat softens the grease, and hot asphalt and heavy braking conduct heat into the hub, so bearings on a summer highway run operate hotter than the design figures assume. Tractors making long summer runs put the wheel ends through hours of sustained heat.

Water is the hidden killer. Pressure washers, flooded roads and wash bays force water past seals, and water in the grease turns it milky and washes off the lubricant. Salt then corrodes the races. Container trucks parked near the coast and tippers working the dusty industrial roads of Dammam meet all three, so inspect their hubs more often and check grease condition whenever a wheel is off.

ABS sensors, hub caps and wheel studs at the wheel end

Many hubs carry an ABS tone ring, and the sensor reads it across a small air gap. A bearing with play changes that gap, which is why a worn wheel bearing can set an ABS fault code before it makes any noise. Protect the tone ring when pressing bearings in and out, and after the job check the sensor gap and connector.

Hub caps keep grease in and contamination out, so a cracked or missing cap invites water and sand into the bearing. Inspect the wheel studs while the wheel is off: stretched, damaged or corroded studs should be replaced. Tighten wheel nuts in a cross pattern to the specified torque and check them again after the first short loaded run.

Grease, oil and hub maintenance

Grease-lubricated hubs need to be repacked at the manufacturer's interval, with the grade and type the manufacturer specifies. Do not mix incompatible greases, and do not overfill, because excess grease pushes out through the seal and onto the brakes. Oil-lubricated hubs, found on some axles, need the oil level checked through the sight glass or plug, and the oil changed to the schedule. Either way, a clean hub and a good seal do more for bearing life than any additive.

How to identify the bearing you need

• The bearing numbers stamped on the inner and outer races.
• The inside diameter, outside diameter and width, as a cross-check.
• The hub and axle model, or the trailer axle plate.
• The seal's outside diameter and width.
• The chassis number, for European trucks.

Wheel bearing questions from workshops and fleets