Weight-weenies are old hat. Friction-weenies are the new Ki

[rhinochopig]

..ngs

A few years back I used to joke with a mate about well his bike rolled. I would have to pedal while he coasted and I used to joke that, as we both worked in Engineering, he'd acquired some exotic bearings from somewhere.

It seems, however, our joking wasn't far off the mark. I've seen a few article expounding the benefits of ceramic bearings and how much friction loss there is in a bike's drive train. Some articles were claiming up to 4w can be 'recovered' by using ceramic bearings, which is a lot at the top levels of competition. Interestingly one article pointed out how much more friction an external BB has over the traditional sq-taper type design due to seal drag and increased bearing contact area; stiffer yes, but harder to turn.

Anyone racers dabbled with replacing your wheel bearings etc. with ceramic versions?

Discuss.

[Kermit power]

I was thinking about this just yesterday evening.

Not, you understand, thinking I could become a high level racer if I just fitted ceramic bearings, but enjoying just how much better my new bike glides.

My road is absolutely dead flat, and if I come on to it at 15mph and stop pedalling, the new bike goes far, far further than the old before running out of steam. Narrower rubber, brand new bike, much more recent groupset of a similar level (Campag Centaur new vs Shimano 105 old), all making for lower levels of friction on the new bike.

[itsnotarace]

The problem is two fold

1) Ceramic bearings are considerably more expensive than steel bearings
2) Ceramic bearings wear out a lot faster than steel bearings

So yes, ceramic bearings do make a difference in reducing drag. But they require more maintenance and deeper pockets to run.

Common areas they are used in:

Hubs
Bottom Brackets
Jockey wheels

[rhinochopig]

itsnotarace said:

The problem is two fold

1) Ceramic bearings are considerably more expensive than steel bearings
2) Ceramic bearings wear out a lot faster than steel bearings

So yes, ceramic bearings do make a difference in reducing drag. But they require more maintenance and deeper pockets to run.

Common areas they are used in:

Hubs
Bottom Brackets
Jockey wheels

I thought they lasted longer because:

• They're rounder
• I thought they had a much higher Rockwell score than steel, i.e. much much harder
• They don't corrode.

I'm not saying you're wrong, just curious to know what the wear mechanism is that means they don't last as long.

[crisisjez]

My oh and I both have new Boardman Team carbons (hers is the fi) both have exactly the same components with the exception of crank length.
I am 35kg heavier than her and as a result I can coast for far longer and even coast past her whilst she has to pedal to keep up.
Sadly I cannot put this down to ceramic bearings

[mat777]

It might be ok for road racing bikes, but I have heard that ceramic bearings crumble/shatter when shock loaded (ie a big pothole on road, or off road biking)

As for rolling friction in general, though not a weenie, I do keep my tyres pumped up very hard and also choose treads with minimum off-road bias I can get away with for the trails I ride, so that I dont have a draggy ride when commuting there and back, or using my bike elsewhere during the week

Edited by mat777 on Wednesday 16th May 00:43

[shouldbworking]

My road bike is the worst for keeping rolling. Compared it to an 80s peugeot road bike and the drag on mine is just unbelievable. The cause? rubbish seals on the loose bearing hubs, maybe 4000 miles on the wheels, braking surfaces have loads left but the bearing races are going to necessitate replacement long before then.

[itsnotarace]

rhinochopig said:

I thought they lasted longer because:

• They're rounder
• I thought they had a much higher Rockwell score than steel, i.e. much much harder
• They don't corrode.

I'm not saying you're wrong, just curious to know what the wear mechanism is that means they don't last as long.

A lot of ceramic bearing manufacturers do not recommend for bicycle use because ceramic is designed for low impact & high rpm's, and in bicycle use it's the opposite - low rpms and high impact.

http://weightweenies.starbike.com/forum/viewtopic....

[rhinochopig]

itsnotarace said:

A lot of ceramic bearing manufacturers do not recommend for bicycle use because ceramic is designed for low impact & high rpm's, and in bicycle use it's the opposite - low rpms and high impact.

http://weightweenies.starbike.com/forum/viewtopic....

Ah, it's the shock load that kills them then. Interesting. More snake oil for the bike industry.

[itsnotarace]

Yes pretty much. Bearings in hubs and bottom brackets take uneven side loads when you are pedalling - especially out of the saddle when sprinting - you can see this yourself when your brake tracks hit the pads if they are adjusted too close. Ceramic bearings have much finer tolerances and require very precise preloading. Which is fine if you have a mechanic stripping and rebuilding your bike after every ride. Jockey wheels are a good place to have ceramic bearing upgrades as they don't suffer from the side loading so much.

[rhinochopig]

itsnotarace said:

Yes pretty much. Bearings in hubs and bottom brackets take uneven side loads when you are pedalling - especially out of the saddle when sprinting - you can see this yourself when your brake tracks hit the pads if they are adjusted too close. Ceramic bearings have much finer tolerances and require very precise preloading. Which is fine if you have a mechanic stripping and rebuilding your bike after every ride. Jockey wheels are a good place to have ceramic bearing upgrades as they don't suffer from the side loading so much.

I actually have some KCNC Jockey wheels with ceramic bearings. I doubt I'd notice the difference between steel and ceramic but I wanted a set for their resilience to clogging and at the time the ceramics were not much more expensive and I was curious about the difference.

[Gooby]

I have ceramic bearings in my '5. BB, Headset and jockey wheels. They last so well. Over 2.5 years old and no play and no wear. Standard steel bearings lasted about 8-11 months. They spin! They sipin so very well! Just wish I could find a set of ceramic bearings for my hope hubs and some for the XTR pedals.

[rhinochopig]

Gooby said:

I have ceramic bearings in my '5. BB, Headset and jockey wheels. They last so well. Over 2.5 years old and no play and no wear. Standard steel bearings lasted about 8-11 months. They spin! They sipin so very well! Just wish I could find a set of ceramic bearings for my hope hubs and some for the XTR pedals.

You can get hybrid (ceramic balls and metal races, although most are this design) hope bearings off ebay from the US.

http://www.ebay.co.uk/sch/jbosboom/m.html?_nkw=&am...

No idea what they're like though.

[JuniorD]

Read an article last year in a cycling mag about Contadors low friction set up: including pedals that rotate freely if you even blink at them sort of thing. I think it said there was little or no grease or lubricant used in the bearings but they were rebuilt every day by his mechanic. I suppose the cumulative effect might save a few watts or have a positive psychologic effect but probably insignificant compared to other gains he might have been able to avail of.