Weightweenies Rejoice - Justification for our Obsession!

Discuss light weight issues concerning road bikes & parts.
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by morrisond

I found this on 53x12.com Michele Ferrari's training site

"1. Light weight: It’s easy to understand what a determining factor the weight of your bike can be when you ride uphill: the force of gravity becomes the cyclist’s principal obstacle.
In truth, weight is also important during accelerations, not only for the obvious ones when you bolt from a group in an attack or to go into a sprint, but also for the ‘micro-accelerations’ that occur with every uphill pedal stroke, especially at reduced speed and pedal cadence.

Five hundred grams saved on the weight of the chassis and non-moving parts translate into an advantage of about 30” for every hour of climb; an even more determinant factor is the weight of wheels, crankset and pedals: every 100 grams saved correspond to an average gain of 20” per hour of climb.
The rotational inertia of the crankset, wheels, and pedals resists every angular acceleration of these same moving parts, with an added energy cost depending on their mass."

Pretty significant if it's accurate.

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by mises

The micro accelerations have always been my argument too, though I have made no attempt to quantify them, and Ferrari's numbers seem pretty high to me.

All the naysayers maintain that once up to speed there is no more acceleration and rotating weight become no more important than static weight. However ever since I first went up a major climb on my computrainer and saw the kph flickering up and down with every pedal stroke it was pretty clear acceleration is always an issue even without wind, pavement, draft and other environmental changes.

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by PNuT

i would say those figures are absolute rubbish

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by asphaltdude

What's the problem with micro accelerations when climbing? With every pedal stroke your bike accelerates a bit. But between the pedal strokes it will decelerate..... With a heavier bike the speed will be more constant, that's all.... of course a lighter bike will climb better, but when riding uphill with constant speed it won't matter wheter you have a 1300 gram frame and 300 gram rims or an 1100 gram frame and 400 gram rims.

By the way, I have seen studies which show that even on a relatively steep climb a heavier, aerodynamic wheelset is faster than a light, non-aero set. (But LightWeigths are both light AND aero :D )
Whow! That's a pretty damn nice garage door!

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by morrisond

According to John Cobb, Lightweights aren't that Aero. Although Drag may have a bigger effect than rim Weight as remember the top of the rim is travelling a twice the speed of the bike relative to the air, which if your climbing at say 15km/h the top of the wheel is travelling at 30'km/h where drag is a factor. Rim weight is still important as this is the mass you are accelerating. Extreme example would be two bikes with same shape wheels and same overall weight, however one bike has 1100 gram Tubs say lightweights with 115 Gram Tufo's and weight added to the frame vs. Cosmic Carbones with 300 gram training tires, I don't think anyone would disagree with the statement that the bike with the light wheels would be easier to ride up the hill. I know I can feel the difference going up a hill on the same bike with Supersonics vs Vittoria Open Corsa's (only about 75 gram difference).

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