by 1965Cobra427 » Tue May 24, 2011 2:21 pm
On Brammo Atoms (at least) the seals are a separate part from the bearings which are not sealed. Grease leaking is a failure of the seal and may not mean a problem in the bearing, except that insufficient grease may lead to a bearing failure. Another possible cause of grease leakage is overheating the brakes. On any Atom, this would take very hard track abuse with slicks, high temperatures and very long sessions on a tight track. It is possible under these extreme conditions to heat the brake rotor and wheel hum assembly sufficiently to "melt" the grease, allowing it to escape the seals. Once the assembly cools, it will go back to not leaking further, but the wheel bearing grease should be replaced, along with the seals.
Once again on Brammo Atoms, there is a tendency on the rear for the bearing spacers (which were not hardened as they should have been) to peen down. This would loosen up the clamping load of the rear axle nuts and you can find many references to wheel bearing failure, rear upright failure, etc. on the forum, many containing my own experiences. The first indications of this include slightly sloppy wheel bearings (IE: tire can be "wiggled" slightly). This is best done with the tire off the ground, since the weight of the car will mask it otherwise until it has reached a much more advanced level of deterioration. Tightening of the rear axle nut is also a good way to check, but of course this requires a sizable torque wrench and a big socket, neither of which are laying around most folks' garages.
Worn spacer
On Brammo Atoms, if you do replace the rear wheel bearings, be sure to check the condition of the bearing spacers. If they are not perfectly smooth on their faces, they should be replaced. I'm pretty sure that TMI can furnish the correct hardened bearing spacers for a reasonable price.
Schematic diagram of rear hub/bearing/axle, etc.
By the way, having damaged and replaced at least three axle sets of rear bearings, I have yet to have any issues with the fronts, which are still as delivered from Brammo. The front are very lightly loaded at about 275# of vehicle weight on each front tire so if these bearings are just well lubricated, they should last a very long time.
On Brammo Atoms (at least) the seals are a separate part from the bearings which are not sealed. Grease leaking is a failure of the seal and may not mean a problem in the bearing, except that insufficient grease may lead to a bearing failure. Another possible cause of grease leakage is overheating the brakes. On any Atom, this would take very hard track abuse with slicks, high temperatures and very long sessions on a tight track. It is possible under these extreme conditions to heat the brake rotor and wheel hum assembly sufficiently to "melt" the grease, allowing it to escape the seals. Once the assembly cools, it will go back to not leaking further, but the wheel bearing grease should be replaced, along with the seals.
Once again on Brammo Atoms, there is a tendency on the rear for the bearing spacers (which were not hardened as they should have been) to peen down. This would loosen up the clamping load of the rear axle nuts and you can find many references to wheel bearing failure, rear upright failure, etc. on the forum, many containing my own experiences. The first indications of this include slightly sloppy wheel bearings (IE: tire can be "wiggled" slightly). This is best done with the tire off the ground, since the weight of the car will mask it otherwise until it has reached a much more advanced level of deterioration. Tightening of the rear axle nut is also a good way to check, but of course this requires a sizable torque wrench and a big socket, neither of which are laying around most folks' garages.
Worn spacer
[img]http://i66.photobucket.com/albums/h269/SuperCobraBuilders/UTC/Spacer1.jpg[/img]
On Brammo Atoms, if you do replace the rear wheel bearings, be sure to check the condition of the bearing spacers. If they are not perfectly smooth on their faces, they should be replaced. I'm pretty sure that TMI can furnish the correct hardened bearing spacers for a reasonable price.
Schematic diagram of rear hub/bearing/axle, etc.
[img width=526 height=600]http://i66.photobucket.com/albums/h269/SuperCobraBuilders/Atom%20Upgrades/HubSchematic-1.jpg[/img]
By the way, having damaged and replaced at least three axle sets of rear bearings, I have yet to have any issues with the fronts, which are still as delivered from Brammo. The front are very lightly loaded at about 275# of vehicle weight on each front tire so if these bearings are just well lubricated, they should last a very long time.