Low friction bottom brackets - are they really worth it?

Bhima

I've just seen some very expensive bottom brackets with ceramic bearings. These are supposed to be low-friction, therefore, you should go faster using them, compared to normal ones (for any given power output).

Are these worth it though? How much less friction is there in these? A massive ammount? I doubt it........?

Surely, any friction decrease in the bottom bracket could be completely irrelevant if you go out on a wet day and get a load of grit in your chain/gears - causing more friction.

GavH

Was looking at these myself the other night. What could ceramic bearings and £200 possibly do for me that a bit more training couldn't? Found a FSA one on an online store, Wheelies i think, which said that ceramic bearings offer a 4% increase in speed for a given effort. Obviously an advantage for racers but i'll use the two hundred quid for something else thanks. I've no idea what the durability on them is like?

DomPro

A 4% increase is quite significant for just changing the bottom bracket. But I just got a conventional one thats quite new so won't be changing for a while.

Monty Dog

Yup - poor drivetrain maintenance wipes out any efficiency gains

tenor

Many people on this Forum get really excited over the odd 100 grams, or so, which represents only about 0.125% of typical bike&rider mass, and is only 'felt' uphill.
So a 4% gain in efficiency should get an amazing response to this thread - but I can gaurantee it won't.

nasahapley

I'd hope most people on this forum would realise that a 4% gain in speed for a given level of effort just by changing your bottom bracket is wildly optimistic marketing hype. Maybe if the bb you're comparing the fancy 'low-friction' one to is absolutely rubbish to begin with or utterly knackered, way beyond the point that you'd normally replace it, then maybe you'd see a 4% increase. But if you've got a decent, well maintained conventional bb already then I'd bet the difference was marginal at best.

Bhima

Yes, that 4% rule sounds like rubbish. Nothing gives the same percentage difference at any speed, because the rules change for different speeds. Maybe at extremely high speeds, you may get close to 4% and you may cut a few seconds off a hill climb but at lower intensities/speeds, the percentage difference will probably be almost nothing.

Bhima

By the way, i'm guessing that the figure referrs to the bottom bracket by itself - so it'll have 4% less friction than a conventional one.

Once you add a load to that (wheels etc), the percentage is less significant.

nasahapley

Yeah, 4% less friction than a conventional bb is much more believable. But then there shouldn't be much friction in a bb anyway, as that's the whole point of them! I thought (might be wrong) that a well-maintained quality chainset would be fairly close to 100% efficient, so even if the flash bb was totally frictionless it wouldn't translate into significant performance gains. But y'know, if you've got the cash burning a hole in your pocket and have already tarted up everything else on your bike...

juggler

tenor wrote:

Many people on this Forum get really excited over the odd 100 grams, or so, which represents only about 0.125% of typical bike&rider mass, and is only 'felt' uphill.
So a 4% gain in efficiency should get an amazing response to this thread - but I can gaurantee it won't.

Do you actually ride a bike? Number of times I read posts such as this 'why pay £x for a bike which is so many grammes lighter when you can just loss weight'. Weight offthe bike is way more significant than weight of the rider. Try riding a steel framed bike, then a carbon or equivalent framed bike... It is about the bike in this case... Dropping a few pounds from your beer belly won't acieve the same result.

crankycrank

I'm posing a question as much as an answer here. As a former motorbike racer I've seen plenty of discussion on the advantages of ceramic bearings. Most seem to feel that the biggest advantage of ceramic is it's durability under high stress-high heat applications such as in a high performance engine. Not something a BB is exposed to so much and that the lower rolling resistance is negligable compared to high quality steel bearings. I'm no expert on this so if anyone has more knowledge on the subject please correct me.

Monty Dog

Pop the seals of your steel bearings for the same effect and save yourself a bundle! My experience of ceramic bearings is with inline skates - you run 16 at a time, but apart from a different noise, the advantage is pretty marginal. Ceramics aren't maintenance free either - in fact to keep them sweet, you use oil not grease which means regular cleaning and lubing.

Monty Dog

Pop the seals of your steel bearings for the same effect and save yourself a bundle! My experience of ceramic bearings is with inline skates - you run 16 at a time, but apart from a different noise, the advantage is pretty marginal. Ceramics aren't maintenance free either - in fact to keep them sweet, you use oil not grease which means regular cleaning and lubing.

maddog 2

I recently went from a standard Shimano BB cups to Hope ceramics (CRC flood sale)

are the Hopes smoother? - yes

do the cranks spin faster? - a bit

can you tell on the bike? - nope

as always, you really need a magazine to test these things but, as always, their testing is woeful