|The MGA With An Attitude
FRONT WHEEL BEARINGS, Design -- FS-112
FS-112 deals with the function, care and feeding of the front wheel hub ball bearings.
At 06:25 PM 3/15/02 -0500, Steve Morris wrote:
">.... The caged ball bearings that have no bias as to direction of side load (and in fact will tolerate *very* little side load) are generally called radial ball bearings.
>Laurie is referring to ball bearings designed to take a side load as well as a radial load. These are called angular contact ball bearings. They have a much higher tolerance for side loads, at a slight cost to radial load rating.
>Thrust bearings are strictly for axial loads and have no tolerance for radial loading."
I second these comments, except that radial bearings often can take a fair amount of side load. Not always a lot, but considerably more than "very little". How much thrust load they can take depends largely on how deep the grooves are in the raceways, and whether there is a side slot for loading the balls.
>"I haven't taken the hubs off of my A yet to swap them out, but I am surprised to find that there are only radial ball bearings in there. I expected to find angular contact bearings when I take it apart. What takes the side loading in the front suspension?"
These particular bearings have quite deep grooves in the races, so they will take quite a lot of thrust load in both directions. They are more appropriately described as unbiased angular contact bearings (can take an equal side load in either direction). These bearings will in fact take a side loading just about equal to the radial loading, which makes them good for wheel hubs.
For the record, the wheel bearings on your MG are very rugged bits of machinery, and when treated properly will generally have a very long life. When they do fail it is almost always because of lack of lubrication (neglect) or from contamination (bad seals allow water to enter and rust the bearing races).
When I restored my MGA (the first time) at about 150,000 miles, I cleaned and inspected and repacked the front wheel bearings and reinstalled them with new seals. Thereafter I clean and repack them about every 20,000 miles or so. At around 250,000 miles some of my SCCA acquaintances doing tech inspections were commenting that the front wheel bearings were a little loose and should be adjusted. They weren't swayed much by the fact these are ball bearings with both inner and outer race spacers, are not adjustable, and are supposed to have a little internal clearance. It didn't bother me, but to humor the techies I installed a new set of front hub bearings. To my surprise, nearly all of the bearing clearance and wiggle disappeared. I was satisfied for a few weeks, until I put another 1000 miles on the car, at which time the clearance and wiggle in the front hub bearings was right back to the way it was on the old 1/4 million mile bearings. And in the next 80,000 miles it has not changed one iota. So in retrospect I figure those new bearings were probably a waste of money. You might chalk this up to peace of mind, but being the frugal and curious type that I am, I would be happier if the original bearings were still in there so I could continue "testing" and have the chance to see if they might outlive me.