Ceramic freehub bearings?

[PLuKE]

Evening guys and gals

My freehub bearings have failed, my mechanic gets me my bearings, which are of fantastic quality ceramic bearings.

I currently have full ceramic balls/races in my wheel set, is it worth getting them in the freehub to help RR?

I know there is a big force on the freehub, so i wouldn't want them to fail.

Opinions?

[goodboyr]

Waste of money. Find out why your original ones failed. They really shouldn't. Low use area. ( unless you coast a lot.....)

[PLuKE]

Well. I have a pair of Campy Bullet 80s, infant 3 sets!

All 3 failed within 50miles, they became notchy. So the last set I kept, and spoke to a Campy Pro shop, and now get non bike generic bearings.

So only a matter of time them bearings went, there cheap crap, on a fanatic wheel/rim, All in my opinion!

[eric]

On most modern hub designs the freehub bearings are turning unless you're coasting. These hubs are really a hub and a freewheel next to each other on a common axle with only the pawls connecting them. When pedalling, all four (or five) bearings turn. However rider weight is on the hub bearings while the freehub bearings only have to deal with forces from pedalling. So I prioritize hub bearings over freehub bearings.

The typical hybrid ceramic ball bearings sold for bicycle use have looser seals in order to feel 'fast' to people examining them. This allows contaminants in and reduces bearing life significantly. I have had a few that last however. I'd go with high quality steel bearings unless your mechanic has experience with these ceramics and knows they'll last. Especially if the bike is ridden in the rain.

[goodboyr]

I think you have it backwards. Freehub bearings only turn when you coast. When you pedal, the pawls lock and the free hub rotates with the axle, and thus the bearings don't turn.

[eric]

It's a common misconception but I have it correct for the majority of hubs. Take some apart and you will see they are built as I described. The original DA freehub did indeed have the freehub turning on an extension of the hub, so the freehub bearings only turned while coasting. But they stopped making them that way a while back. That was the only one I know of that worked that way. Extralites have a hybrid where the outer freehub bearing is on the axle and turns when pedalling while the inner bushing (now bearing) is between the freehub and the hub shell and turns when coasting. I think there's one other manufacturer that does this.

[eric]

Here's a cross section I found:



This one has a roller bearing (#15) on the left side of the freehub where most have a ball bearing. But you see that the freehub bearings are on the stationary axle. #17 is the right side freehub ball bearing. #9 is a combines inner race and spacer for the roller bearing. Both freehub bearings inner races are on the non rotating axle, so they turn when the rider is pedalling.

[goodboyr]

Thanks for that info. So, I took a spare zipp hub and axle and also a spare fulcrum zero hub and axle, and what I see is in both cases, the axle runs right through the inner races of the freehub bearing. So, when coasting, the free hub is stationary and the axle spins. So, as I see it, that causes the freehub inner race rotates when coasting. When pedaling the freehub locks to the axle through the pawls and rotates at the same as the axle. So, in these two cases, there is no additional "non rotating axle" between the inner race of the bearing and the axle. Here is the fulcrum diagram. The small cylinder between the two bearings in the freehub is a loose fit.

[Delorre]

Sorry, but an axle spinning when the wheel is locked in the dropouts Or you formulate it wrong, or.... The axle if fixed, and when you pedal, the freehub locks with the hub body, but continue to rotate around the axle. And, since the bearing underneath the freehub is the only one that support the freehub when applying force on the pedals, those bearing have better be of good quality. I've had worn out bearing in the freehub of my shamal ultra's, and I can guarantee you, the harder you push on the pedals, the worse things get, and it's like riding with flat tyres

[goodboyr]

Duh!!!!! Got it. I guess it's me being Friday stupid. Appreciate your patience and explanation. Thanks!

[PLuKE]

You both started to confuse me!

From a text book point of view, its best to have ceramic bearings in the freehub, to maximise a lower RR?

Luke

[goodboyr]

I stand by my original statement. Although my credibility is shot to hell. You want well sealed bearings. I still would not recommend ceramic.

[micky]

+1

Not worth the money.
Better save them for something else.

[PLuKE]

Thanks for your comments.

I am awaiting prices of SS, Hybrid and ceramic bearings, see what the cost is and make a call.

Luke

[kavitator]

Quality good sealed steel bearings - go on FrictionFacts and see what is important for save wattage

About which bearing turns: axle is fixed with skewers - hubbody bearings always running - freehub only when peddaling
In classic hub design (DT swis, Tune, ...) most load has inner freehub bearing. On picture below is hub for MTB (XC or cyclocross) - and forces are bigger so manufacturer put needle bearing in that place. Some manufacturers put two bearing in that place