A question for you wrenchies…
How easily should Dura ace cranks “free spin”?
I’ve just finished putting a bike together, but am surprised at how less easily the cranks spin than on my campag equipped road bike… the bottom bracket bearings seem surprisingly stiff. I understand that free spin is not necessarily an indicator of performance underload, so is this something I should worry about… any idea what could be wrong…? I’ve taken out the bottom bracket and it doesn’t seem to spin any freer.
I’ve heard it takes some miles to break them in first.
Grant
Mine is like yours even with ceramic bearing…
What you are experiencing is completely normal. All external bearing BB’s spin like that… Some a little better than others (Campy has the best “spin factor,” but still not much) but they are all relatively sluggish compared to inboard BB’s with cartridge or loose ball bearings. They all claim that there is no percievable loss in performance…
i went the the process of testing a few bb.s the shimano stock BB’s are the worst and frankly hardly get better with breakin. if youspun the crank, no chain, you’d be lucky to get 1 1/2, 2 rotations.
i then tried Phil Woods bearings in the shimano BB’…maybe a spin or two more.
then i tried enduro ceramics in shimano cups …same thing, no improvement over phil wood.
then i got FSA ceramic BB’s which are 100% fully compatible with shimano cranks…thing spins about 15 revolutions after a few rides.
probably a huge wattage difference. night and day.
A 4% wattage difference according to this http://www.cyclingnews.com/tech/?id=2006/reviews/FSA_MegaExo.
Looks like that’s I’ll be adding something to the “to buy” list…
Thanks for the input everyone.
A 4% wattage difference according to this http://www.cyclingnews.com/.../reviews/FSA_MegaExo.
Looks like that’s I’ll be adding something to the “to buy” list…
Thanks for the input everyone.
I’d save your money. What that article doesn’t tell you is at what wattage will you save 4%? My guess is at 1 watt, the external bottom bracket costs about 4% of your energy (as opposed to 1% for the best bottom bracket). However, it doesn’t increase in a linear fashion–and indeed, it may not increase at all. (After all, BB’s aren’t turbochargers. You’re still only spinning so fast…).
The Velonews test showed that at ‘moderate easy spinning’ wattage, the WORST BB cost about a .04 of a watt. The 4% claim is patently ridiculous applied to real world wattages.
FWIW, after changing to a more freely spinning bottom bracket bearing, my power did not change in any noticable fashion. While I’m sure my current BB is ‘better’, it’s a vanishingly small difference. 4% would be an addition 12 watts at threshold–something I’ve have noticed…