Originally Posted By: DriveHard
I worked as a bearing engineer for over 5 years, and there is some mis-information here...
If the hub is a pre-set assembly, then it should never loosen up unless there is a manufacturing defect.
The chance of getting a "true brinell" in an automotive application with rubber tires is slim to none. Chances are that the growl was the start of some spalling, or perhaps false brinelling caused from ingress of water and having the rollers rust small lines into the races.
While the tapered bearings will more than likely last longer from a fatigue standpoint, the truth is that most automotive wheel bearings fail from seal ingress long before they fail from fatigue. I know for a fact that Timken does some great seal research and testing when selecting the seals for their pre-set assemblies. SKF is a worthy competitor though, and they are both quality products.
If you do lots of sporty driving, or haul heavier than normal loads, I would go with the TImken. If you don't I would inspect both bearings, and choose the one that appears to have the better seal quality.
Since I have been running the Camaro on race tracks for 11 years, I can assure you that I have a real-world testing machine in rolling contact fatigue. AC Delco and Timken hub assemblies would loosen up in about a year of track days, and I was pretty much resigned to changing them every spring until I tried the SKF's. The major difference that I could see was the housing on the SKF was turned down where the outboard bearing was mounted, and must have allowed for better load sharing between the inner and outer bearings.
I hear what you say about brinelling, but don't expect that manufacturing defects or seal failure could have occurred on all of the bearings I have had on the front of the car. Maybe the extra heat from heavy braking is causing the seals to fail? Regardless of the cause, I will continue to do the wobble test on my front wheels. Perhaps you would like to ride with me when I dive into turn 12 at Road Atlanta at 105 mph in a car with loose wheel bearings?
Rear axle bearings have also been a problem. I could only count on a life of 50k miles on the axles, at which point they would start growling, and I would install a new set of axles, bearings, and seals. I finally got fed up with the GM C-clip axle design, and had Moser build a hybrid rear end. This setup still uses the stock 7.5" ring gear 10-bolt axle housing, but has adapters for Ford 9" outboard bearings. The axles are Moser parts for 9-inch Fords, but have been modified with splines for the GM differential carrier. I only have a couple of track days on this setup, so it will be a few years before I can say whether or not it's better.
