A hub assembly bolts to the knuckle on one side, holds the wheel bearings, and has the wheel bolted on its other side. In the past, there would have been multiple replaceable and serviceable parts involved; bearings and races, the hub flange or integrated rotor, grease seals, and the spindle. It was also necessary to remove and re-grease the bearings from time to time and to carefully set the bearing preload on reassembly.
The advantage of a hub assembly is that it’s all in one piece, sealed, and no servicing is necessary. Of course, the disadvantage is that if anything goes wrong, the whole thing needs to be replaced. But they are generally very reliable and long-lived parts, and they are also pretty straightforward to replace. Usually, the brakes need to be removed out of the way, then the hub assembly can be unbolted from the knuckle.
On vehicles with ABS, the tone ring and speed sensor are included as a part of the hub assembly. Usually a new hub comes with a new speed sensor installed and tested, so you also need to undo the old sensor wire from its clips and disconnect it, then route and connect the new one in. It is possible to re-use an old speed sensor, but the exact gap between the sensor and the tone ring is critical, and if it is even a tiny bit off, it can cause problems with the signal and disable the ABS.
Costs of Hub Assembly Replacement
On average, the cost of replacing a hub assembly is about £195 for a passenger car and about £330 for a light truck. That includes labour, which is about an hour in most cases.
For some more specific examples of the costs of replacing a hub assembly on some common vehicles, using £70 an hour as a labour rate:
On a 2009 Ford Fusion with a 3.0-litre engine, the labour time to replace the rear hub assembly is 0.9 of an hour. A rear hub assembly costs about £60 for a non-OE part and about £160 for an OE part. This would make the cost of replacing the rear wheel bearing about £125 with aftermarket parts, or about £225 with OE parts. The front of the vehicle uses a cartridge bearing rather than a wheel bearing.
For a 2012 Chevrolet 1500 with four-wheel drive, the labour time for the front hub assembly replacement is 1 hour. The factory replacement part costs about £330, and an aftermarket hub assembly costs about £195. This makes the job about £400 using OE parts, or about £265 using aftermarket parts. At the rear of the vehicle, axle bearings are used.
On a 2004 Camry with a 3.0-litre engine, the labour time to replace a rear hub assembly is 1.6 hours. A factory part costs about £540, and a non-OE part costs about £125. That makes the job about £650 using OE parts, or about £240 using aftermarket parts. At the front of the vehicle, a cartridge bearing is used.
How to Tell if a Hub Assembly Needs Replaced
Almost always, it is the bearings that wear out, so the normal symptoms of a failing bearing are what’s looked for, which would be a grinding noise when the vehicle is moving. Each hub assembly has an inner and an outer bearing. Usually, one or the other will go first, and steering a little one way or the other loads or unloads each bearing in turn. Most of the time, a suspected bearing noise can be checked that way on a test drive; steering one way then the other, the noise should get worse, then better, as the bearing is loaded and unloaded.
Even then, it can be tricky to tell which side the noise is on, as sounds transmit pretty freely through a vehicle. Usually, the car is put up on a hoist and run in gear while someone listens at each hub with a stethoscope to confirm the noise. Other signs are sometimes rust particles shedding from a bearing seal, showing a dry bearing breaking down. Or, if the bearing is pretty far gone, looseness and play at the wheel.
A hub assembly that has a bearing problem should be replaced as soon as possible and driven as little as possible until it is replaced. Too much play can prevent the brakes from functioning normally, and if left long enough, can even allow the wheel assembly to break free. A wheel bearing that is just a little noisy can generate enough heat at highway speeds to experience what we call “sudden catastrophic failure,” which is best avoided.
No. For some years, when hub assemblies became common, it was recommended to check the alignment after replacing one, but there was hardly ever any need. Current manufacturing tolerances are more than precise enough that it’s unnecessary.
There is no normal expected life span and no maintenance that can be done. Usually, if a hub assembly lasts over 100,000 miles (and they usually do), that’s considered decent.
Yes, but it’s not a good idea; the air gap to the tone ring is critical, and can vary enough between any two manufacturers to cause a problem. That’s why new hubs come with new speed sensors installed, if applicable.