The short version
- The parking brake does not hold the front wheels. Most guides get this wrong and it matters at the axle nut.
- On many bolt-on hubs the bolts are reached through windows in the hub flange. Rotate the hub, do not remove the knuckle.
- Take the ABS sensor out first, and twist it rather than pulling. It snaps off in the hole otherwise.
- Never let the driveshaft hang. The inner joint plunges apart and the boot tears.
A front wheel bearing replacement on a bolt-on hub is one of the better first suspension jobs. The steps are logical and nothing needs a press.
A seized wheel can stop it before step one. What follows is the front specific version. The parts that catch people out are almost never the bearing itself.
Front wheel bearing replacement: before the car goes up
Two things happen with all four wheels on the ground, and both are about leverage.
Crack the wheel nuts a quarter turn. Then crack the axle nut. It is usually a large socket, 30 to 36 millimeters, and it often needs a breaker bar with real weight behind it.
Almost every guide says to set the parking brake before loosening the axle nut. But on nearly every car it acts on the rear wheels only. It does nothing for the corner you are working on.
What holds a front wheel is the transmission in Park, or a helper on the brake pedal. Set the parking brake as well, for the rest of the car. Just do not rely on it here.
Chock the rear wheels. Then lift at a rated point and get it onto stands before anything else comes off.
Getting to the hub
Four things come off in order, and the order saves damage.
- The ABS sensor. Usually one small bolt. Take it out now, before it is in the way and before something pulls on its wire.
- The caliper. Two slide pin bolts. Hang it on a wire from the spring, never by the flexible hose.
- The caliper bracket. Two larger bolts into the knuckle, often seized and often high torque.
- The rotor. Sometimes one small retaining screw, then it lifts off. If it is rusted on, most rotors have threaded jacking holes.
You now have the hub face exposed and the knuckle accessible from both sides.
Reaching them is on the hub bolts page. The ABS sensor is the fragile part
This small component causes more grief on a front wheel bearing replacement than the bearing does.
The sensor body sits in a close fitting hole in an aluminum knuckle. Aluminum oxide grows into the clearance and locks it there. It is the same mechanism that seizes the hub itself.
Pull straight up on a seized sensor and the plastic body tears off, leaving the tip in the hole. Digging that out without damaging the bore is a miserable afternoon.
Break the bolt loose, spray penetrating oil around the collar, then rotate the sensor in the hole. A quarter turn each way breaks the oxide bond. Only then lift it, by the body rather than the wire.
If it does snap, a replacement sensor is usually cheap. A knuckle damaged while extracting the old tip is not. Why the sensor and the bearing are so closely tied sits on the ABS integration page.
The bolts you cannot see
Here is the detail that turns a two hour job into a five hour one when nobody mentions it.
On a bolt-on front hub the mounting bolts thread in from behind the knuckle. From the front, all you see is the hub flange and its studs.
Most designs solve this with access windows. Holes are cast or drilled through the hub flange. Rotating the hub lines each one up with a bolt head behind it.
If you cannot see the bolts, turn the hub. One hole, one bolt, then turn again. People who miss this separate ball joints and tie rods to swing the knuckle out, which adds hours and an alignment.
Not every vehicle does it this way and some genuinely need the knuckle off. If yours is a pressed-in design, the press-in procedure is the page you want.
The driveshaft
On a front-wheel-drive or all-wheel-drive car there is a shaft through the middle of the hub, splined into it.
Remove the axle nut, then push the shaft back through the splines. It should move with hand pressure or a soft tap.
If it will not, fit the old nut flush with the end of the shaft before hitting anything. Hitting a bare thread ruins it. Techniques for a shaft rusted into place are in freeing a seized hub.
Once it is free, do not let it hang. The inner joint on most cars is a plunging tripod that can pull apart under the shaft’s own weight. Even when it holds, hanging stretches and tears the boot.
Tie it up level with a bungee or rest it on a stand. Thirty seconds of care avoids a far larger repair.
The dust shield
Behind the hub is a thin pressed steel shield, and it bends if you look at it wrong.
It usually has to come off or be moved to get the hub out, and it goes back on with the new unit.
A bent shield touching the rotor makes a rhythmic metallic sound that rises with speed. It is close enough to a failing bearing to get misdiagnosed regularly. The noise impostors page covers it alongside the rest.
Fitting the new hub
Cleanliness is the whole job here.
The knuckle mating face must be flat and clean. Wire brush the corrosion off and finish with a scotch pad and brake cleaner. Check no raised lip is left anywhere.
A hub sitting on a high spot runs at a slight angle. That produces runout, and runout produces a brake pedal pulse nobody connects back to the bearing job.
A light smear of anti-seize on the register only, never on the mating face or on a thread with a torque figure. Then offer the unit up. Check the ABS connector faces the right way before you tighten anything.
Torque, in the right order and the right place
Three fasteners, three separate specifications, and none of them are guesses.
| Fastener | What it does | When to torque it |
|---|---|---|
| Hub mounting bolts | Clamp the unit to the knuckle | In the air, in sequence, criss cross |
| Caliper bracket bolts | Hold the braking load | In the air, often with thread locker |
| Axle nut | Sets bearing preload | Wheel on the ground |
| Wheel nuts | Hold the wheel | Ground, in sequence, rechecked after a drive |
The axle nut is the one that matters most and the one people get wrong. It is a preload setting rather than a tightness, and an impact gun cannot hit it. Figures run from under 100 to over 300 pound feet between vehicles.
Published charts also disagree with each other more than you would expect. The torque specs page shows that with numbers from two editions of one catalog.
Finishing up
Refit the ABS sensor with a smear of anti-seize on the body so the next person has an easier time.
Pump the brake pedal before you move. The pistons have not retracted, but the pads may have shifted. The first pedal press belongs in the driveway rather than at the end of the street.
Drive gently for a few miles, then recheck the wheel nuts to the specified figure. A front wheel bearing replacement that was done cleanly should be silent from the first mile.
Disturbing the sensor or the encoder ring commonly sets a code. It usually clears once the wheel turns a few times. If it does not, steel debris on the magnetic encoder face is the usual cause.
Whether the geometry needs resetting afterward depends on what came apart, as the alignment page sets out.
Confirming your own work before the wheel goes back on is on the verification page.
Common questions
How do you replace a front wheel bearing?
Crack the axle nut on the ground, then remove the wheel, ABS sensor, caliper, bracket and rotor. Undo the hub bolts through the flange windows, fit the new unit and torque everything to spec. A pressed-in design is a different job needing a press.
Do I need to remove the knuckle?
Usually not on a bolt-on hub. The mounting bolts are reached through access holes in the flange, so rotate the hub to line them up. Pressed-in designs generally do need the knuckle off.
Should I use the parking brake to hold the wheel?
No. On almost every car the parking brake works on the rear wheels only. Use Park, or have someone hold the foot brake.
Do I need an alignment afterward?
Not if you only unbolted the hub, since nothing that sets an angle moved. Yes if the knuckle came off or a tie rod was separated.
Why did the ABS light come on?
The sensor or the encoder ring was disturbed. It often clears after a few wheel rotations, and steel debris stuck to the magnetic encoder is the usual persistent cause.
How long should it take?
Book time is 1 to 1.5 hours per corner for a bolt-on hub. A first attempt on a salted car is realistically half a day. The front cost page shows what the shop version comes to.
Can I do just one side?
Yes. Bearings are not a matched pair, and the two front corners share almost no labor. Doing both costs close to double rather than a little more.