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question(11 posts)

questiondustin
Dec 13, 2001 11:38 PM
which requires more energy:

riding a 23lb bike with no bag;
or riding an 18lb bike carrying a 5lb bag?
re: questionMJ
Dec 14, 2001 1:36 AM
18 lb bike with 5 lb bag - bags flop around
18 lb bike w/ 5 pound bagdzrider
Dec 14, 2001 5:19 AM
You have to support the bag. Either feels easier to me than an 18 lb bike and 5 extra pounds of body weight.
No differencepmf1
Dec 14, 2001 5:23 AM
Both weigh 23 lbs. My question is, what on earth is in that bag? Bringing along an extra frame?
depends on where the 23 pounds areTig
Dec 14, 2001 7:57 AM
The higher center of gravity of the flopping or even stable 5 lb bag on an 18 lb bike would be nothing compared to a very heavy set of wheels. The extra rotational mass of heavy wheels would be the worst case, but I doubt we'll see a pair of 5 pound plus wheels outside of Walmart. Maybe a heavy aerobar hanging on the bars would make handling difficult.
Rotational weight thingy, maybe not such a big deal.Dog Breath
Dec 14, 2001 9:04 AM
You may want to research that further. In bike applications it may not be the issue everyone thinks it is.

Have a look a bike.com or do a search of the google bicycle tech groups, you may change your opinion.

In any case it only affects acceleration negatively.
There isn't any differenceguido
Dec 14, 2001 12:38 PM
It'll just feel different if you put the bag over the rear wheel, on the front wheel, or take it off the frame and carry it in a backpack. The total weight is the same, therefore has the same inertial resistance.
re: questionjosh_putnam
Dec 14, 2001 4:41 PM
You don't give enough information to provide a definite answer.

Where's the extra 5lbs distributed on the 23lb bike?

What sort of bag is the 5lbs in on the 18lb bike?
re: questiondustin
Dec 14, 2001 5:24 PM
the extra 5lbs is distributed in the heavier frame, components, yadda yadda.

type of bag...backpack.
re: questionjosh_putnam
Dec 15, 2001 4:43 PM
It's a tossup without much more detailed information, and most likely the difference is going to be miniscule anyway.

A reasonably aerodynamic backpack won't add too much wind drag compared to the sort of clothing usually worn with a backpack, certainly less drag than panniers, for example.

If the components are just heavier, but not lower quality, they shouldn't add much drag. But many heavier components also use lower-quality bearings, so the heavier bike might have more power losses. Expecially if the heavy bike has cheap tires -- tire casing flex can burn up a lot of energy, one reason narrow, high-pressure tires feel so much faster even on heavy rims.
The bike with the bag doesDAC
Dec 15, 2001 5:51 AM
Because, the bags create more air drag, of course! Otherwise, 23lbs=23lbs!