Originally Posted by
Mark Kelly
Read my description again. We are in agreement, I never argued for a torque on the hub.
It is simply a matter of changing spoke tension with applied force. I actually think the problem is worse than I said becasue it would apply to the wheel simply supporting the weight of the rider as well.
Maybe I'm misunderstanding you. I'll try to phrase your argument in my own words and you can correct me where I'm wrong.
You are saying that during braking, leading spokes at the top of the wheel will increase in tension while trailing spokes will decrease. On the bottom of the wheel you are saying the reverse will happen (trailing spokes increase in tension, leading decrease). This change in the balance of tension will cause the dish of the wheel to change.
I disagree on all points except that a change in tension balance will cause the dish of the wheel to change. That much is true. However, the only way to create an imbalance in the tension of this proposed wheel would be to apply a torque to only one hub flange (as would happen on the drive side of the rear wheel or the disc side of a disc braked wheel). Leading spokes can do nothing to counter a torque applied to the hub that cause a tension increase in the trailing spokes. As a result, they lose tension.
However, when a person sits on a bike, the spokes pointing up increase in tension while the spokes pointing down decrease in tension. Similarly, during rim braking, the spokes pointing rearward increase in tension while the spokes pointing forward decrease in tension. Leading/trailing makes no difference in these scenarios. At any given time, there are both leading and trailing spokes pointing up, down, forward, and back.
Back to the proposed wheel. When a person sits on a bike with a wheel laced like that, the leading and trailing spokes pointing up will increase in tension. The difference between this increase in tension compared to a standard wheel is the lack of complimentary spoke pulling on the opposite side of the same hub flange (a crossed wheel will one spoke pulling up on the rearmost side of the hub flange while another spoke pulls up on the forward side of the hub flange and this is happening on both hub flanges). When one spoke is pulling up on the rearmost side of the hub flange while a spoke on the other side of the wheel pulls up on the forward side of the hub flange, the result is the hub shell shell getting twisted like a pretzel. Insert top and bottom of the hub flange for the forces happening during rim braking.