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Testing friction change in full-ceramic-bearing jockey pulleys

Lennard Zinn drops by Friction Facts to test the full-ceramic-bearing jockey pulleys on his cyclocross bikes after a muddy season

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The first time I ever spun a Tiso full-ceramic-bearing jockey pulley was at Interbike a couple years ago. I was amazed at how I could flick it with my finger and it would spin and spin and spin and spin some more. It was amazing. I’d never seen a jockey wheel do anything of the sort before.

Full-ceramic bearings have ceramic balls as well as ceramic inner and outer races. This is in contrast with “hybrid ceramic” bearings (common in high-end hubs and bottom brackets), which have ceramic balls and steel inner and outer races. The latter can of course still rust, and they require good seals and lubricant to prevent grit from getting into them and scoring the steel races. The grease and the seals definitely create drag, and there is no way the Tiso pulleys could spin that long and fast unloaded if they had seals and grease.

The ceramic parts in full-ceramic bearings are purportedly so hard that grit caught in them eventually becomes crushed or ground up! Presumably this would not be the case if were to you ride your bike inside a diamond mine, but out on the street, they should be harder than the grit that might contaminate them.

The Tiso full-ceramic-bearing jockey pulleys have no cover seal whatsoever over the balls. When I got some for my cyclocross bikes, their distributor, Albabici, told me not to worry about them being open to the elements and not to lubricate them at all. I have not.

After using the Tiso full-ceramic-bearing jockey pulleys in the mud and grit in cyclocross all season without cleaning or lubricating them, I fully expected them to become as resistive to turning as standard bushing-type pulleys. But I noticed during the season that whenever I pulled the chain off and spun them, they still spun better than any other jockey wheel I’d ever had.

Naturally, I wanted to test them for frictional drag. Friction Facts in Boulder is the perfect place to do it, so I headed over there with a pair that had taken a pounding and lots of washings all cyclocross season.

The last time these particular jockey wheels had been used or washed was at cyclocross nationals in early January. All season, I never put any lubricant on them, and I never cleaned them other than with a hose or a pressure washer while washing the entire bike. After I removed them from the bike, Friction Facts founder Jason Smith rinsed both of the pulleys under the faucet, spinning them while the water was flowing. He allowed them to thoroughly dry in front of a fan for six hours; then he formally tested both of these used full-ceramic-bearing Tiso jockey wheels, as well as a new one, on his Reactive Torque Pulley Tester (RTPT).

We compared the results on the used pulleys with the results on a new full-ceramic-bearing Tiso jockey wheel. The results are as follows:

New Tiso: 0.016 watts
Used Tiso No. 1: 0.042 watts
Used Tiso No. 2: 0.027 watts
Total power loss for the pair of used Tiso jockey wheels: 0.069 watts.

Here is a description of the test apparatus and protocol:

The three graphs at the top of this page show the test results in watts for each of the three pulleys. The spikes on the screen prints are from Smith setting up the pulley and attaching the load to the strain gauge. The stable line on the right hand portion of the screen is the pulley reading.

I was privy to a jockey-wheel friction test that Friction Facts performed a number of months ago on a whole range of pulleys of various brands and models. In comparing with those results, I could see that my used, abused, and not lubed Tiso full-ceramic jockey wheels, while exhibiting much more drag than they had when new, still would have placed in fifth place, behind the new Tiso full ceramic and three others. They still out-performed 16 other new jockey wheels, some of them by over a watt per pair! I’d say this is really good, considering a season of racing and no seals and no lube. However, this is a subjective opinion. It sure was nice never having to do any maintenance on them, though! I usually dismantle, clean and lube my bushing-type jockey wheels every couple of months.

If you want to see how your jockey wheels stack up, you can purchase Friction Facts’ test results on 19 different derailleur pulley models for five bucks. Given the cost of some of these high-end wheels with ceramic bearings, that seems like a modest investment indeed before making a pulley purchase.