Front Wheel Bearings
By Ron Bramlett

(from our January 2001 Newsletter) 

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   Believe it or not, many of the questions I field from Mustang owners concern wheel bearings, either directly or indirectly. Yet we see very little in the way of written material on them in the Mustang magazines. So I decided to do an article on them for the Mustangs Plus Newsletter.

    I'll cover front wheel bearings in this issue and rear wheel bearings in the next issue. Yes, I know. Wheel bearings sound boring. But stay with me here! Knowing a few things about wheel bearings can help you with many things, from safety to gas mileage.

   The front wheel bearings used on our classic ‘65 to ‘73 Mustangs, as well as most other American cars of the era, are all of the same design. However, because of model changes and manufactures upgrades, slight differences mean that they are not all interchangeable. Diameters, both inside and outside, are usually the relative differences.

    Each front wheel has two wheel bearings; an inner and an outer. The inner bearing is the larger of the two. Front wheel bearings are of the "cone" variety (we'll talk about this later), consisting of two pieces called a bearing and a loose race. The "loose race", as we call it because it is a separate piece from the actual bearing, is flat on one side and has a tapered face on the other where the roller bearings ride. The loose race presses into the front wheel hub.


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This photo shows the both parts of the "cone" style front wheel bearing and its four components: the loose race, roller bearings, cage, and inner race.


    The brake drum, if you have drum brakes, or the brake rotor, if you have disc brakes, is attached to the hub. The loose race is designed to be a very tight fit and taking care not to damage it during installation is a must. Once it is installed, and you've made sure that it's all the way down in the hub, you're done with the loose race until the next time you change wheel bearings.
   The other part of a front wheel bearing is the actual bearing itself. The bearing is made up of three parts. An internal race, the roller bearings, and a cage. Like the loose race, the internal race has a tapered face and this is where the roller bearings ride.  
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The photo on the right shows the difference in size between the outer bearing, which is the smaller bearing, and the inner bearing, which is the larger.


   The roller bearings are held in place by a window mesh liner called the cage. The cage has three functions, To keep the roller bearings held to the internal race so that they can not fall out during installation, to keep the roller bearings the proper distance from each other during operation and to allow the proper amount of grease to stay in the bearing while it is in operation. Since front wheel bearings are not  sealed bearings, you must pack grease into them, either by hand or by machine, before they can be used.

    Now that we know a little about front wheel bearings, let's see how they impact the way our Mustangs drive and stop!

frtbr03.gif (50652 bytes)    As I stated earlier, many of our handling and braking questions end up being answered by front wheel bearing problems. These problems usually occur after new front wheel bearings have been installed.

    There are two reasons for this. The loose race was not seated all the way into the bottom of the hub or the wheel bearings were not tightened properly when they were installed. Remember I said that the faces of the bearing races were tapered? Because of this taper, the front wheel bearings must be "loaded" when the brake drum or rotor is installed. Loaded simply means that the nut, which holds the brake drum or rotor to the spindle, is tightened the proper amount. The tighter the nut is, the more inward force is put on the bearings. Too much force is bad. Too little force is also bad. The trick is to get to the middle ground. Front wheel bearings being too tight or too loose impacts the driving and braking of your Mustang as well as wheel bearing life.

        If your front wheel bearings are overtightened, the bearings have to run under too much pressure. This results in friction which causes heat, and lots of it! Heat leads to premature bearing wear and early failure. It heats the grease up to the point where it can actually run out of the bearing. If left undetected, the heat can damage not only the wheel bearing, but the spindle and the hub, too. Also, since the tire and wheel is harder to turn, gas milage can be reduced. It's like having the front brakes slightly on all the time. If one side is too tight and one side is too loose, the car will pull to the tight side during normal driving and braking.

    To check to see if your front wheel bearings are too tight, jack the car up and, with the tire off the ground, grab the tire and spin it. It should make a couple of revolutions before stopping. You should also hear the brake drag slightly on the drum or rotor. If it doesn't make one full revolution, make sure the brake isn't too tight. If it's not the brake, it's time to take it apart and check the wheel bearings. After disassembly and cleaning, if the bearing, spindle, or hub have a blue tint to them, they have been overheated. The deeper the blue tint, the more heat the part has seen.

    Any wheel bearing showing signs of being overheated should be replaced. You've already got it apart and wheel bearings are cheap. In the case of an overheated spindle or hub, you should have them checked by a reliable shop who does front end and brake work as they may not be safe to use again.

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