Non-benz question about hub bearing
 

Question for the mechanics out there

I have a question just replaced a hub bearing on my honda a few weeks back......brand new bearing.....had machine shop press new one in......tonight I heard a thunk when I drove slow over rough stretch of road.........jack car up a few minutes ago adn that same bearing is shot again...15" wheel has about 1/2" wobble at the tread, not loose lugs....the whole hub is moving around from bearing apparently self destructing ....last time it was the outer side that went....assume its outer side again. Caliper is not sticking and bearing required no shims to replace....there is in effect nothing that preloads it.

THe bearing is a big and beefy one about 2 inches wide really a double ball earing on a common outer race. Any ideas what could cause a failure so soon?

If a ball bearing self destructs in such a short period of time, my opinion is that it is heavily preloaded. What this means is that the bearing has too much interference with either the outer housing and/or the inner shaft.

When the bearing is forced into this position, it is very highly stressed internally and will quickly fail. Ideally, when the bearing is in service, there is a small clearance between the rolling elements and the raceways. Without this clearance (interference), the bearing will appear to function properly, but will not last long in service.

This is especially true with bearings on automobiles that have no ongoing supply of coolant and must rely on the grease in the housing for lubrication.

Before installing the bearing, make very sure that the housing is perfectly clean. This may require some sanding with emery cloth to remove any high metal. Any corrosion inside the housing, that is not thoroughly removed down to the base metal, will cause this condition.

You could also measure the housing and measure the bearing prior to installation, if you have the proper tools. You would be looking for minimal interference; .0005 to .002 as a maximum. But, you cannot do it with a vernier caliper, so, this is not a very good option.

When we deal with installation of balancing bearings for jet engines we must maintain an interference between the bearing and the housing of .0005 to .001. Any more than this, and the bearing won't survive. Any less than this and the machining tolerances might allow a clearance. :eek:

PM me if you need to discuss it further.

You have a PM ................

Spot on Mr. Carlton
 

I just replaced a set of double roller front wheel bearings on a Mazda Protege that were replaced less than 500 miles earlier. The shop failed to properly clean the housing and ended up with dirt keeping the bearing from seating. It got hot and the grease ran out causing the premature failure.

This car probably shares a few things with BHD's race car. Transplanted Honda S2000 engine. Turbo charged with intercooler and nitrous oxide. 5 speed limited slip. Race car suspension. Fast little bugger. Nice little car.

This same advice applies to the tapered roller bearings on the front spindles of our MB's. M/B likes to keep the clearance inside the bearing down to about .0005 inches. This is an incredibly small value, but, is more than enough to allow the bearing to perform flawlessly for years.

But, if you make an error during installation, and you slightly overtighten the collar, and the .0005 clearance goes below zero, the bearing will fail within the first 5,000 miles, or less. :eek: :eek: