Originally Posted by gregf83

No, it was correct the first time. The primary effect of weight is a slightly slower climbing speed proportional to the added weight as a percentage of total weight. It doesn't matter whether the extra weight is on the rims, in your bottles or on your head, a 250g increase will slow a 70kg rider down by about .3% (11 seconds slower on a 1 hour climb).

Added rim weight may be noticeable in the parking lot accelerating from a stop but it's insignificant (relative to weight in your bottle) when it counts, i.e. in a sprint at the end of a race due to the relatively low accelerations occurring in a real sprint. You'd be far better off riding a deeper, heavier rim with better aerodynamic properties even if it had a little higher inertia.

The amount of energy stored in a wheeling spinning at 30-40kph is very low and not worth worrying about.