Hubs, old vs new?

[bikenut2010]

Maybe you've just been eating more pies than them?

While there can be a noticeable difference in hub smoothness when turning the spindles by hand, hub friction is way down the list of things that csn affect speed when out on the road. Aerodynamics and weight are far far more important when freewheeling downhill.

pies? moi?

 

[tonyf39]

'glpinxit' You've fallen into the common misconception that we live in a vaccuum, we don't thus mass does matter in this instance and the heavier overall mass WILL achieve a higher speed on the same slope.
As it happens overcoming wind resistance is by far the biggest factor, multiple times over anything else. Body position, an ill fitting or open jacket, pannier bags, helmets (for those that wear them ) wheel/frame design..the list goes on.
Tyres & the much ignored proper tyre inflation have an influence as do hub quality/ bearing choice and how much actual wear in the hubs.
Some ceramic bearings (notably FSA's latest outboard BB cups) have far more resistance than even a bog std shimano Octalink. In wheel terms I have a Sansin sealed bearing hub and a Mavic 501, the are both smoother rolling/longer lasting than hubs made in the last 5-10 years.
Campag bearings I believe used to be bought from SKF (possibly even FAG), and this definitely shows in their hubs/bottom brackets from the 70s through to the 90s, very smooth rolling.

 

[torqueless]

Thanks Tony...
I was just about to mutter something about physics on an inclined plane being different to objects in free-fall, (without really knowing what I'm talking about.. :? ) As an extreme example, if you have a wooden ball and a steel ball of the same diameter, rolling down a ramp, I think the more massive steel ball will reach the bottom of the ramp before the wooden ball?.. In the 'real' world, at least. Ask someone with more physics than me whether you get the same result in a vacuum...

 

[tonyf39]

yeah, Newtons 2nd law and all that stuff, here's a pretty good layman's terms explanation for those bothered enough
http://www.physicsclassroom.com/mmedia/ ... s/efar.cfm

I reeled in a fair few 'carbondaxer's' on a downhill a couple of years ago whilst not even touching the pedals (on my flat bar spesh with two pannier bags..lol), firstly cos I've a lot more mass than them, 2ndly I know how to descend half decent and thirdly I know about aerodynamics and when tucking is required over just powering down a hill in 53/11 which can work out quicker though is less aero.

ATEOTD do what feels good for you and if you get left or catch up on the slopes just be thankful if there are no tin boxes in your way to spoil your racing line

 

[Donny Dee]

I've found the fastest rolling set of modern hubs to be Campag Record 2013 and light too.

 

[Donny Dee]

And not that dear!

 

[bikenut2010]

ah that's worth checking out, my 'modern' wheels are scirocco ...

 

[bm0p700f]

I think we need to apply some physics.

For a bike rolling down a hill it's weight and that of the rider is a big factor. Yes g = 9.81 m/s^2 but there air resistance.

Rolling down a slop the gravtitaional force F = mg sin (theta) where theta is the angle of the slope.
So total force is F = mg*sin(theta) - (0.5)CdA*ro*V^2- mgCrr

So the mass of the bike is a factor in fact the heavier the bike and the rider the faster they will go down a hill.

A hub even a Royce hubs with contact seals will only comsume 1W or so more at speed than a good cup and cone hub.

 

[bikenut2010]

Interesting, I was trying to make a weight for weight comparison...my mate is over 6ft on a basic Trek 1.2 with guards, about the same weight as me (5'8" on a Colnago SL C record hubs ), he was pedalling to keep up on quite a shallow gradient, same with several other riders...

 

[foz]

mudguards are very un-aero. assuming the total weight of each bike+rider is the same, then the difference will be in aerodynamics (and descending ability, if it's not just a long straight hill)