When it comes to the hub assembly, heavy-duty trucks and trailers have many moving parts—all of which are critical to your wheel end. At Wheelco Truck and Trailer, we want to keep your downtime to a minimum, but your safety is essential. Therefore, it’s important for you to understand the importance of wheel bearings in your hub assemblies. We’ll also discuss detection and diagnosis as it relates to wheel bearings issues. Some of our top questions include:
- What are wheel bearings, and why are they important?
- How do wheel bearings work?
- Can I diagnose or detect wheel bearing issues?
- How can I tell if my bearings need replacement?
- What do I really need to know about Wheel Bearing Preventive Maintenance?
What are Wheel Bearings and Why are They Important?
Wheel bearings allow your truck’s wheels to rotate with minimal friction. They also carry a brunt of your vehicle’s weight and take loads from every direction. So, if you want a smooth ride, make sure your wheel bearings aren’t damaged. Keep in mind that these are wearable parts and will eventually fail if not replaced.
How do Wheel Bearings Work?
Wheel bearings reduce friction, from the tire and wheel, with the hardened steel balls (rollers) and a smooth inner and outer metal surface (inner and outer race). The race provides a smooth surface for the rollers to roll across. The rollers “bear” the load and support the front and rear axle of your heavy-duty vehicle as you drive along the road.
*Images used with permission from SKF
Wheel Bearing Components
There are a few main components in a tapered bearing set. They include one cup and one cone. The cone consists of three main parts: cage, rollers, and inner race.
Bearings and Seals Quick Guide
At Wheelco, we recommend replacing both the cup and cone (bearing sets) when necessary. Why? Great question. The wear on each component will be consistent, it ensures longer bearing life, prevents premature failure, increases truck and trailer up-time, and helps with the installation process. Contact one of our experts if you need assistance replacing your bearings or check out our Bearings and Seals Quick Guide to see what our team recommends.
Popular Wheel End Lubrication
Make sure you keep your wheel end well lubricated. It dissipates heat, reduces friction, acts as a corrosion inhibitor. It can come in a few different viscosities, depending on your needs. The three types are oil, semi-fluid grease, and hard grease of various grades. If you are replacing your bearings and seals, be sure to pick up proper lubricants to prevent wheel end failures.
Heavy Duty Axle Oil
For heavy-duty vehicles, a common viscosity for oil lubricant is 75W-90 GL5 LS. Popular brands include Shell and SynGard. Engineered for heavy duty manual transmissions and rear axles, it offers excellent load-carrying and shock capability as well as working well in various temperatures and pressures. It meets or exceeds the requirements of the (American Petroleum Institute) API standards.
Heavy Duty Severe Grease Application
When you’re working with heavy duty equipment for on and off-road applications, we recommend using Hi Temp EP 2 Red Grease. Xtreme™ Heavy-Duty Synthetic Blend Hi-Temp Grease #2 is engineered for industrial applications, construction and agriculture.
What Causes A Wheel Bearing to Fail?
When you stop driving your truck, the wheel bearing cools. This cooling causes the bearing to contract. As it does the air and lubricates around it can create a vacuum that is held by your seal if the breather is plugged. Should the seal fail, the bearing or sealed hub unit will suck in outside air, debris, and water. Debris like salt (on winter roads) dirt, metallic flakes, and other tiny particles from the road wreak havoc on your bearings. Debris collects in the grease and lubricants. It gets circulated through bearings. If this happens, your seal and bearing can no longer keep out contaminants and wear rate is accelerated. Common seal related failures include poor or improper lubrication, contamination or poor fitting.
However, there are other factors that causes wheel bearings to fail like:
- Excessive loading
- Impact damage
- Improper lubrication
Check out other common wheel bearing failures to look out for on your next wheel bearing inspection.
Is Wheel Bearing Failure Dangerous?
Is it safe to drive with a damaged wheel bearing? No!
If you even suspect that your wheel bearing may be failing or damaged, we urge you to contact a service technician immediately. Even if you aren’t near one of our shops, we urge you to call. We’ll do our best to help you locate a service center to get your truck fixed.
How to Diagnose or Detect Wheel Bearing Failure
Loud Noise or Roaring
The most common symptom indicating a wheel bearing has gone south is a loud noise or “roar.” It comes from the wheel hub assembly. It’s often described as a “metal on metal” noise. It will often get louder the greater the speed.
If the steering wheel of your vehicle feels “loose,” vibrates or wobbles excessively can be an indication that a wheel bearing has gone bad. This is an unsafe situation. Vibration or even lack of directional steadiness can mean that your bearing is near failure.
Axial or Radial Play
Axial or radial play in the wheel or wheel hub is another sign that a bearing is damaged or wearing out. Should the wheel hub move up and down or in and out, the bearing may need to be replaced.
Rough Movement in Wheel End
Tire and wheel assembly does not turn smoothly is another indication your bearings may be damaged. To test this possibility: jack up your wheel, ensure the truck is not in gear and that your brakes are not dragging. You should be able to rotate the wheel smoothly. Should it be rough, have inconsistent movement, or make sounds, is an indication of possible damage to your bearings.
Progressive Wheel Hub Damage
If your bearings are failing, it is possible that other parts in the wheel hub assembly are not working properly either (or even damaged). If the bearings won’t allow the wheel to turn freely, it will strain the hub, the axle, the transmission and more.
Wheel Bearing Inspection & Maintenance
Detailed inspections should be done every 12 months or every 100,000 miles. However, you should conduct preventive maintenance before and after driving your vehicle.
Quick Tip! If you suspect your wheel bearing may be damaged after you’ve been driving, feel the hub immediately after departing the vehicle. If one hub is hotter than the others, it should be checked for bearing damage. Why? Great question. The additional drag, produced by worn out bearings, will generate hotter than usual heat. Normal operating temperatures ranges between 175 to 200° F.
Bearing Cup Inspection
The tapered raceway surface inside the cup is the most commonly damaged area of the cup. Upon inspection, look for the following:
- Sliding (caused by hard abrasives)
- Metal etching (an indication of water contamination)
- Dents (impact damage)
- Corrosion (develop in spalling)
- Grooving (caused by particles in the lubricant)
- Dings in the bearing surfaces (improper installation)
- False brinelling (repeated effects of vibration)
- Surface arching (electrical arching from welding)
- Roller end fracture (loose bearing adjustments)
- Roller wear (over tightening, lubrication degradation or lack of lubricant)
- Roller end cracks (excessive loading or misalignment)
- Scoring (caused by dirt, debris, or metallic flakes)
- Discoloration (an indication of overheated bearing)
- Wear marks (mild abrasive wear)
Bearing Cone Inspection
The cone consisting of (taper) rollers, a cage, and inner race. At Wheelco, we recommend that you slowly rotate the cone assembly as you inspect the assembly. Careful inspection and look for the following:
Bearing Cage and Inner Ring Inspection
The bearing cage can be damaged by careless use, like being throwing into a box or dropped on the floor. Poor installation caused by hammering the component is another common cause of damage. Dirt, misalignment and insufficient lubricant can also cause damage. Make a careful inspection and look for the following:
- Metallic debris
- Metallic flaking
Technology & Maintenance Council (TMC) of American Trucking Associations Recommended Practices Library Links
- 2018-2019 Recommended Practices Manual (Complete Integrated Set)
- 2017 TMC Recommended Practices Supplement
- 2016-2017 TMC Recommended Maintenance Practices
- 2016-2017 TMC Recommended Engineering Practices
What are the Top Brands in Bearings?
Wheelco recommends using top-quality bearings for your safety and up-time. We trust brands like Hyatt and Timken. If you need more support or insight, our experts are happy to help! Give us a call or stop by one of our retail stores.