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PostPosted: Mon Jul 16, 2012 12:46 pm 

Joined: Mon Jan 02, 2012 8:09 pm
Posts: 39
A discussion at Superweek yesterday and this question was posed!

Wheel A is 58mm deep and weights 1450 grams

Wheel B is 38mm deep and also weight 1450 grams.

Is rotational weight the same or is it easier to spin up the shallower wheel due to cutting through the wind on acceleration?

Does it make no difference as to depth if their the same weight?

It almost seems like its hard to start a sprint or acceleration on deeper wheels of the same weigh!

PostPosted: Mon Jul 16, 2012 12:58 pm 

Joined: Sun Mar 27, 2011 10:01 pm
Posts: 96
I would've thought that the deeper wheel is easier to spin since less of the weight is on the outer edge (hence less force required to rotate it). However, since the weight distribution is so small (12mm) the extra depth might be causing a drag effect that overpowers the beneficial effect from having the weight closer to the hub.

PostPosted: Mon Jul 16, 2012 1:02 pm 
Formerly known as wassertreter

Joined: Tue Apr 12, 2011 8:08 am
Posts: 2238
Location: Pedal Square
Not enough information to do the calculation, you need to know where the mass is. Imagine one wheel having internal nipples, then the spoke bed would be farther out, meaning more inertia.

Not that I think it would make a difference in real world.

Bikes: Raw Ti, 650b flatbar CX

PostPosted: Mon Jul 16, 2012 1:35 pm 

Joined: Tue Sep 14, 2010 3:28 pm
Posts: 1405
Rollers are the best way for someone to see for themselves how much impact wheel inertia is having on there accelerations. Try out a few different wheels using the same protocol, and then the next time wheel inertia comes up you'll find yourself doing :roll:

PostPosted: Tue Jul 17, 2012 2:35 am 

Joined: Sun Sep 03, 2006 1:55 pm
Posts: 1838
Location: Western Australia
It's likely that the deeper wheel will have a lower moment of inertia. Wassertreter is 100% correct though. Not enough info.

However, the difference in practice would be so small and the aero advantage with a deeper set would be greater that the better choice really is the deeper set. All things considered, unless a shallower set is significantly lighter, aero is better.

Cyclist turned music producer

Visiting South West Australia? Visit Crank n' Cycles!

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