You might carry an extra wheel bearing and a new grease seal with you every weekend you're at the track but the real problem is that a bad wheel bearing can destroy a spindle. I bet you don’t have one of those in your weekend parts inventory.
Checking on Bearing Wear and Condition
Checking on bearing play should be a part of your race prep program. You need to do this every time you go to the track. Usually nothing will be wrong but you need to do it just the same. A bad wheel bearing at the track usually means you get to go home early.
The quick and dirty way is to raise the front wheels off the ground. With one hand at 12 o’clock on the wheel and your other hand at 6 o’clock try to move the wheel back and forth. If you feel the play is excessive you might start taking things apart for inspection or you can use a dial indicator gauge on the wheel to actually measure the play.
While the wheel is in the air spin it and listen for noise. Good bearings don’t make noise. If your wheel bearings pass both the wiggle test and the noise test you’re in pretty good shape.
Inspecting the Bearing
Before you attempt to grease your wheel bearings you need to clean them. Really clean them. You can use mineral spirits or acetone as a final rinse. Just make sure you get all of the old grease out of the bearing.
If you find any pits or bluing in the bearing race you need a new bearing. Now do the same with the bearing itself. Once again if you find pits or bluing you need to replace the bearing. There really aren’t any tolerances here. Your wheel bearing is either good or it’s bad.
Replacement
You only need to replace the wheel bearings if they fail this visual inspection. Always replace the bearing and the race as a unit. Generally they’re only sold as a set but I’m starting to see some races and bearings sold separately. Especially trailer bearings.
If you replace them you'll need to make, or buy, some tools to pound out the old races and press or pound in the new races. The outer race is usually a press-fit while the inner race slides tight on the shaft. More than a few people have damaged their hubs trying to press in a new bearing race. You can buy a bearing installation tool kit for about $150.00. It makes the job a lot easier and you minimize any damage you might cause using the old bearing race as an installation tool. You might even be able to borrow a bearing installation from your local parts house. Heating the hubs in your oven also makes installing the bearing race a lot easier.
Greasing the Bearing
Bearing grease is made up of three components: A base fluid, a thickening system and an additive system. The type of base oil is the most significant property. Grease created with synthetic oil is generally thought to be superior to grease with a mineral oil base, but even that is contested by a couple of oil companies.
Soap is added to this base oil to create wheel bearing grease. This soap acts like a sponge to keep the oil in place. The most common soap used for wheel bearing grease is a lithium complex. Higher quality soaps will allow the grease to withstand higher temperatures.
Chemical and metallic additives are added to grease in order to enhance their performance, much like the additives added to lubricating oils. Performance requirements, compatibility, environmental considerations, color and cost are all factors in additive selection.
An interesting case study in bearings is the high-speed train in China. The bearings overheated when the train exceeded 100 mph. Royal Purple as asked to supply a suitable product for this train. In a twenty-day test they were able to reduce bearing failures by 50 per cent. The train was also able to set a new Chinese speed record of 200 mph. It was all about synthetic oil and top quality soap. Nothing was wrong with the bearings.
Read the Label
National Lubricating Grease Institute developed standards for the quality of grease. You should look at your can of wheel bearing grease for the letters NLGI GC-LB. NLGI GC-LB is the highest performance category for multipurpose greases. GC refers to the highest wheel bearing performance classification, while LB refers to the highest chassis classification.
Also check the label for something called the Drop Point. Drop Point is the temperature at which the oil drops or separates from the soap. You want at least a 5000 drop point. Some companies are producing wheel bearing grease with a 9000drop point.
You might also see NLGI #2 on the label. The number 2 is a scale created by the National Lubricating Grease Institute to measure the viscosity of industrial grease. The NLGI scale ranges from 000 to 6, with 000 being the most fluid grease and 6 the most solid. Wheel bearing grease is normally #2.
There are two different designations for chassis greases (LA and LB) and three classifications for wheel bearing greases (GA, GB, and GC). Royal Purple suggests that you can use wheel-bearing grease for your chassis fittings but you shouldn’t be using chassis grease for your wheel bearings. That means just buy a top quality wheel bearing grease and use the same lube for your chassis as well. How hard can that be?
