Originally Posted by
No Chain
Are you sure about that? I had it explained to me once like this: When riding your bike, your spokes are not "holding you up", or "resisting forces from the outside", rather your hubs are hanging from the top spokes as your wheels spin. I'm no physicist, but that makes sense to me. How can a few thin pieces of wire hold UP a 200lb. man, plus a bicycle frame and whatever weight he has lashed to it?
By that rationale, hanging a bike from a hook produces exactly the type of stresses the wheel is designed to handle while being ridden. The only difference I can see is that the wheel is not spinning, rather hanging from the same couple of spokes (whichever happen to be on top). But, the bike alone also weighs much less than bike + rider, so you are ahead of the game in that regard. The same thing is happening when the bike is sitting stationary on the floor, so I fail to see the difference. The experiences of many posters who haven't had problems hanging their bikes for extended periods of time tend to support this theory.
Maybe I'm not explaining it right, or maybe I just don't understand. If any physicist out there has the definitive answer, please let us know, as I intend to hang many bikes from hooks when I move in a couple of weeks...
Originally Posted by
ItsJustMe
The spokes are ALWAYS resisting forces pulling in that direction. It's the spokes on the TOP half of the wheel that take the weight in normal riding. With the amount of tension in the wheel (I don't know how much, but I bet it's a ton per wheel easily), the weight of the bike is inconsequential. I bet you could hang YOUR weight from it for a year and not see any deformation. If you start pushing sideways on the bike while it's on a hook, yeah, that could cause damage, but not straight pulls.
Incorrect. The wheel stands on it's spokes. However, it is the tension of the opposing spokes that allow the "bottom" spokes in this model to maintain the tension of a pre-stressed structure, but in no way is the hub "hanging" from the top spokes. Whoever "explained" that to you has no concept of how a pre-tensioned/pre-loaded structure operates. This highly erroneous concept - the hub "hanging" from its top spokes - seems to be self evident, but it is similar to believing that the sun orbits the earth: What appears self-evident is not always true. A wire spoked wheel works like a wooden one except that the built in forces are different; instead of gaining in compression, the bottom spokes lose tension. But the algebraic sum of negative and positive forces is the same. Only the bottom spokes change length under load, but they are rigid so long as they maintain tension. Wire used as a compression member is similar to prestressed concrete in this way; the prestressed concrete with steel beams appear to be acting in tension, but concrete cannot work in tension any more than wires can work in compression. But, it is the internal stretched steel that ensures that the concrete never experiences tension - only if the tension force is enough to overcome the prestressed condition of the steel beams, at which point the concrete will crack. Structurally, the bottom spokes are acting as compression members until the compressive force overcomes the tensile force pre-loaded into them. The concept that a wheel "hangs" from its spokes contradicts every mathematical and experimental model on pre-stressed wire spoked wheels. I highly suggest reading Mr. Brandt's very informative book on the subject, and then reading the FEM data in the appendices.
However, the correct part of this discussion is that the hooks will not affect your wheels at all. On a 36 spoke wheel, the combined spoke tension compresses the rim with a force equal to nearly one half ton. (See equation 7 in part III of "The Bicycle Wheel"). Even if your bike is a 40lb beast, you are not going to overcome that force.
The only potential damage would be if you twisted the bike while a hook was holding the wheel to such a degree as to untrue the wheel; in this case the damage would be analagous to catching your wheel in recessed tracks, or a crack, or something similar.