|Do sealed cartridge bearings need to "break in"?||Eug|
May 23, 2003 6:58 AM
|OK, I'm being obsessive, but...
I just replaced the sealed cartridge bearings on a 1998 Cane Creek Aerohead (new and never used - don't ask). The bearings alone cost me US$45 yet the wheel rolls very slightly worse than my 2002 Tiagra.
Mind you, the Tiagra Matrix Aurora wheel is significantly heavier, as is the wire bead tire (25), so it might be partially a momentum thing. (The Cane Creek has a Kevlar bead 23.) However, I don't think it would fully explain it and thus it is a bit disconcerting. Do I notice it in real life? No, but like I said, I'm obsessive...
Would a "break in" period change this? (These are supposedly good quality mid-end cartridges. I can provide the exact brand & model number later.)
May 23, 2003 7:30 AM
|Sealed cartridge bearings use a tight-fitting seal on both sides, to prevent contamination. The lips of the seals may be dragging on the inner race, and will relax slightly as they're used.
I'm not real familiar with the Tiagra hub, but I suspect it uses a couple of sealing rings (like piston rings) on the bearing cones. These don't actually touch the hub shell, so there's no friction, and thus the bearings feel smoother. Whether they really are or not is a matter of the bearing roundness and race smoothness, but it really comes into play on the road.
All that being said, it makes no practical difference. Once you're at speed, bearing drag and tire rolling resistance stay constant, while wind resistance increases as the square of velocity, I think. Meaning that above maybe 10 mph, aerodynamics eclipses all other power losses, which is also why time trialers and triathletes run deep-section heavy wheels.
|re: Do sealed cartridge bearings need to "break in"?||eddie m|
May 23, 2003 7:58 AM
|The seals on the cartridge bearings may be causing a little drag, but they will work in over time. It's pretty difficult to get an accurate measurement of actual drag in a wheel bearing. If you are holding the wheels off the ground and spinning them, and observing which spins longer, you won't get a valid comparison. First, the heavier rim will spin longer. Second, without your weight on the wheel, the bearing friction is less then it would be on the road. In a test like that, a heavy wheel with its bearings adjusted too loosely will usually spin longer than the best racing wheels. The friction of the bearing seals is also more of a factor in that type of comparison then it actually is on the road. If the cartidge bearings run smoothly, even if they seem to have a little friction, they will be fine.|
|Bearings are NSK 6900VV||Eug|
May 23, 2003 3:49 PM
|The bearings the store bought are NSK 6900VV AV2S 109. Anyone know anything about these? I couldn't find it on the website.
The stock bearings that the hub came with are Enduro 6900RS.