Washington, D.C. Centre
Tech-Tips
Home
About
Join
Board
Calendar
the Spark
Gallery
Tech-Tips
Regalia
Classifieds
Links
Contact

CHECK YOUR BEARINGS - Part I

by Jim Lunson

 

I had a recent surprise with my MG that turned out to be a good learning experience. Took my MG in for its annual safety inspection as required by Virginia and failed. Seems the inspector jacked up the right front tire, grabbed it at the 3 and 9 o'clock positions, pulled on it and noticed some wobble. Needs new tie rods he exclaimed and slapped the reject sticker on the windshield.

Back home I inspected his findings and sure enough, by jacking up the right front wheel and pulling on the tire at the 3-9 positions, there was some wobble. But I noticed there was also the same wobble when I grabbed the tire at the 6-12 o'clock positions. Wobble in the horizontal direction could mean the tie rods, but in the vertical direction it would have nothing to do with the tie rods and instead indicates wear in the front wheel bearing. I got to remembering that I had completely rebuilt the front suspension when I first got the car, but that was now almost 20 years and 35,000 miles ago, so it was time to look at the bearings again.

The bearings in the MGB are very strong, but are of a unique design. Most cars use a method of seating the front wheel bearings by simply tightening the large slotted nut on the end of the shaft until the bearing tapers are squeezed together on the shaft to the point they restrict spinning, then back off the nut until free spin is achieved and then back the nut off a little more to line up the slots in the nut with the hole in the shaft and reinsert the cotter pin. This setup works but only if the perfect adjustment occurs exactly at the spot on the nut where the cotter pin can be inserted does this adjustment method give a perfect fit. Otherwise a little play is always present in the adjustment. Not an exact way to get the best fit with wheel bearings and why bearing wear out.

Instead of this system, the MG bearings are adjusted using a steel tube spacer and then inserting shims (washers of varying thickness) over the shaft to adjust the spacing between the inner and outer bearings to provide an exact tight firm fit. The adjustment with these shims is made down to the .001 inch. The hub nut can then be tightened very tight (40-70 ft-lbs) and locked in with a cotter pin wherever it lines up. The system is firm and is adjusted precisely to the space needed between the bearings allowing them to spin very precisely with no play or wobble. This setup yields minimal wear to the bearing over the miles. It is one of the best designs on the entire MG.

So remember, every so often check your front bearings, and wobble in the vertical direction probably indicates there are too many shims spacing the bearing sets too far apart allowing for the wheel to move on the shaft in addition to spin. In my case, the adjustment was good when done 20 years ago, but due to wear over the miles, a new adjustment was necessary. Ill go in to the steps to make the bearing adjustment in the next issue. Suffice to say that after making corrections to these shims, I then checked the left tire, and performed the same exercise. Then back to the inspection station and passed. No wobble whatsoever. And no work was needed on the tie rods or steering system either.

I usually fear the annual Virginia safety inspection and have thought about switching to the antique plate which eliminates this hassle, but I havent done it as the inspection does serve a purpose as demonstrated by this little episode. An added benefit to this incident over and above a safety issue is that I noticed as I drove back to the inspection station the car seemed to roll easier, truer and the steering felt like I had rebuilt the entire front end again. Amazing how the gradual wearing goes so unnoticed. So dont wait for an inspection, check your bearings sometime, and make sure you dont have any wobble in the vertical direction. And dont panic if you get rejected some time at your friendly inspection station for front wheel wobble. If its in the vertical direction, it can usually be easily adjusted.

 

Back to Technical Tips

Home