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Common Questions About Bearing Installation

WHEEL END BEARINGS - The Most Common Installation Questions

My hubs have a spacer in them, what do I do?

The ConMet® hubs (standard on most new trucks) come with a spacer thats designed to set the end-play for that set of bearings. Over time, due to spindle flex, wear and become shorter. Therefore if they are used with ANY bearing replacement, your bearings will likely be too tight and possibly result in a bearing pre-load condition which is dangerous and has been known to cause catastrophic hub failure and fires. The company specifically recommends that they not be re-used since they are sized for the factory installed bearings.

The Stemco nuts seem pricey, do I really need them?
We feel they're essential. And that's for two reasons. One, because of spindle flex, having an adequate amount of end-play is essential for maximum bearing life and performance. And two, due to the fact that end-play cannot be measured with a dial indicator when a seal is installed, there is no accurate and consistent way of adjusting wheel hubs and more importantly, knowing what the end-play is set at. The Stemco® Pro-Torq adjustment system is the only way we know of to get this consistently correct.

Can I use MicroBlue® bearings with unitized, one-piece hubs?
Unfortunately no. They are a one-time assembly that are not designed to be rebuilt, and have no replacement parts available. A word of caution. The typical lifespan of those units is about 800,000 miles and many report that they give no "warning" when they are about to fail. That warning many times comes in the form of the wheel coming off. Were serious about this and if you have in excess of 500,000 miles on a set, check regularly for any signs of excessive wear.

Can I use MicroBlue® bearings with my super-singles?
Absolutely. In fact, they are the best choice because of their extraordinary wear properties, they will withstand to the greater stresses the singles create. Especially with offset wheels. They will also perform far better than other recent bearing designs that claim to be designed for that application.

Do your bearings come pre-lubed?
No, they are shipped with a light rust preventative coating on them. It is important to apply a light coating of any oil during installation.

What about lubricants then. What's the best choice?
Due to the "lubricant magnet" properties of the MicroBlue® coating you are now able to use thinner lubricants than before. For steer and trailer hubs, we have found that any common 50 wt. synthetic transmission oil is fine. There is no problem using a 75/90, you just do not need to. The thinner oil will decrease rolling resistance. We do recommend using a full synthetic, especially in northern, colder climates.

What information do I need to order the correct bearings?
For tractor applications, we will need the make, model, year and the last 8 numbers of your VIN. For trailer applications, there are only two spindle types; tapered and straight. The overwhelming number of trailers use tapered spindles, but it is best to check with the people you purchased the trailer from. They will know.

How do I know if the bearings were installed correctly?
We feel the best way is to do it the same way race teams go, measure your hub temperatures with an inexpensive infrared temp gun. We have found that over-tightening of bearings is much too common in this industry. And due to spindle flex, we know that "tight" makes heat. In general (with exceptions), we expect to see them running roughly 15-30 deg./F. over the ambient temperature. So if it's 80 deg. we're looking for something from 95-to 110 deg./F. In the two years that we have been monitoring this, we have found that for every .001" of end-play we lose (from .004") we see an average of 5 deg. temperature rise.

Is there any warranty with MicroBlue® bearings?
Absolutely. In fact you can have two of them. In addition to our three-year, 300,000 mile warranty against defects and workmanship, if you elect to use a Stemco® seal and hub cap, they too will warranty the bearings as well as their seals for three years as well. Now that's hard to beat.


Con-Met Bearing Spacers

Stemco Pro-Torq Adjustment Nut

A Must For Every Trucker


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