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Wheel Bearing Tone Ring – Tech Corner

As new cars get more complicated, and more car parts become integrated systems, there are an increasing number of ‘gotchas’ when it comes to putting your car up on jackstands and replacing parts.  This is one that results in a phantom ABS check engine light after replacing the wheel bearings, and is not as straightforward as you may think.  Granted all cars are different and some of these will be more obvious than others.  The ABS light is triggered by lack of signal from the tone ring, a sensor ring that allows the wheel speed sensor to detect the speed that the wheel is turning by counting the time between notches.  On most cars, these rings are external, located on the wheel hub assembly or CV joint.  However, there are a handful of cars that feature wheel bearing tone rings that are invisible, located inside the sealed wheel bearing.

If you accidentally install one of these wheel bearings with an internal tone ring backwards (many standard sealed wheel bearings don’t have a specific orientation), your ABS sensor in the spindle won’t have a signal to send to the ECU, and you’ll trigger the light.  If you’ve ever done a press in wheel bearing, especially without a shop, the ABS light is NOT something you want to be staring at after you do a job like this.  If you do, bust the tools back out, you’ve got to do it all over again.

How can I tell if I have a wheel bearing tone ring?

This is actually a pretty straight forward process.  With things coming apart, observe if you have an ABS sensor on the wheel poking through the spindle.  Then check out the area near the end of the sensor.  If there’s an axle with a toothed ring going around it, or the wheel hub/bearing has a ring with a bunch of holes in it, then you’ve found your sensor and your ring.  If they are dirty, clean them off before reassembling.

wheel bearing tone rings
Many cars use tone rings on the axle or on the wheel hub to give a signal to the ABS. If you see this, you do not have to watch out for a wheel bearing tone ring.

If you don’t see any tone rings and the ABS sensor goes towards the wheel bearing, then chances are you have a wheel bearing tone ring that’s located internally.  When pressing in the new bearing, make sure that you keep the side of the bearing with the tone ring facing towards the ABS sensor or wheel speed sensor.  If it’s not clear which one is which, take a small piece of magnetic metal such as a paperclip, and see which side it sticks to.  That will be the side you want to face your bearing.  Here is a very simplified demonstration on YouTube.

wheel bearing tone ring
The serrations on this BMW X3 wheel bearing is a clue there’s a an ABS tone ring in there. A paperclip should stick to it, install the magnetic site towards the ABS sensor.

eEuroparts carries a variety of wheel bearings, from standard sealed bearings (with and without wheel bearing tone rings), old school taper bearings and the grease to go with them, as well as complete hub and bearing assemblies.  Check out eEuroparts.com next time you need anything for your European car, shipped fast!

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Working on cars is dangerous, always be careful and be aware of the hazards of working on any vehicle. eEuroparts.com (Newparts Inc) is not responsible for any injury, up to and including death, as a result of working on any vehicle suggested or implied on this website.