We have spent significant time investigating hub rolling resistance. (details of our test rig are below) With our test rig we compared steel vs. ceramic bearings, and bearing bore variations. The biggest measurable difference was in bearing bore accuracy. Bores that were not concentric or that were undersized (in the hub shell) or oversized (on the axle) made the most difference. The wrong size bore, even as small as .001" undersized, deforms the bearing race and increases drag. Likewise, non-concentric bores bind the bearings slightly and increase bearing drag. These differences were evident in both an unloaded wheel and one loaded with 100lbs.
There was a measurable drag difference between ceramic bearings and steel bearings when we tested unloaded wheels, but the difference was small enough that we could not measure it on a loaded wheel.
The upshot of our testing is this - We continue to focus on high quality hubs with exact machining tolerances. Ceramic bearings do give a small but measurable reduction in drag. They also offer greatly increased durability and longevity. Based on this they are now an option on our wheels.
How we tested:
In 2006 we built a test rig to measure axle creep on hubs. To understand how it works, picture wheel with an overtight hub. If you were to rest the axle stubs on your extended index fingers and spin the wheel, it would roll off your fingers, because the axle turns along with the rim. Adjusting the bearings correctly lets the rim spin and the axle remain stationary, but even when the axle is adjusted right, there is still a little tug on the axle. If the axle stubs are just resting on a flat surface instead of clamped in a fork the wheel will still slowly roll forward. We designed our tester to measure this axle creep with a loaded wheel (as if there were a rider on the bike) and an unloaded wheel.
Details
Abec3 steel bearings are our stock offering. Grade 5 ceramic bearings are optional. They have ceramic balls and cyrogenically treated races and a double lip LLB seal which lowers drag compared to the normal 2RS seal. Our ceramic bearings are filled with Rock n Roll synthetic grease to reduce pumping drag.
$120 for wire spoked wheel set. (Jet, Stinger, Bastogne)
$76.50 for H3 wheelset.
Factory installed only, either new wheelsets or retrofits.
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