Little Things Part II: Weight

My last entry was about the little things and their significance.

I thought I'd run a few very simple calcs and see if I could quantify what weight looks like on the Clarks climb. If my calcs appear to be off, please point it out.

Having ridden with a power meter off-road quite a bit, I think it is a reasonable estimate that an 11 minute climb up Clarks puts me at about 280 watts. I can do a quick double-check of this. My mass should be right around 84 kgs for body, bike, clothes, etc. My barometric altitude measurements are a little inconsistant, but generally put the climb at about 298 meters altitude
gain. So, neglecting wind reistance and rolling resistance, the average wattage would be 247 Watts. If I was really 280, that leaves something like 33 watts for rolling and wind. This time would put the average speed up the climb at about 3.58 m/s. Extrapolating from some wind-tunnel data done on road bikes, I think the wind drag at this speed is about 8 watts. So this all seems reasonable to me.

With this a background, let's construct a very simple model. Assume rolling resistance is proportional with mass. Add one pound to the bike, so rolling resistance is now 84.45/84*25=25.13 watts. Expending my same 280 watts gives pretty much the same, 246.9 watts for climbing. We could drop this correction and it wouldn't matter much.

Let's also assume wind resistance is unchanged since the speed barely changes. This leaves us with a disadvantage of 4 seconds on the climb for that pound. It is pretty much linear with these small differences, so 4 seconds per pound every 10 minutes is probably a reasonable estimate (for me going hard).

A pound is typically not that easy to take off the bike. Is it worth it? I suspect a race like Evanston has no less than 80 minutes of climbing. This would put us at something like 30 seconds over the course of the race.

If the rider could take 5 pounds off, that would apparently be very beneficial (in the past when I've lost weight I've lost power and it has never come out to my advantage).

It should also be pointed out that bigger riders will pay less of a penality for weight, smaller women considerably more. It would be great to have good information on the the effect of rear-suspension on rolling-resistance to see if it is worth the extra 1.5 lbs typical of current top-end MTB's.

Some people have claimed weight on the body is worse than weight on the bike, or visa-versa. There are only two means by which this would be true: 1) increased rolling resistance, 2) decreased body efficiency due to to cooling or something. Based on the calc above, explanation 1 isn't going to matter. Maybe 2 does, but I doubt it when we're talking about 0-5 lbs over the body. As a separate argument (irrelevant to climbing), some claim the bike handles better if you move weight from the bike to the body (water, mainly). Personally, I've never noticed this.