Originally Posted by
cale
To measure the "effect" of weight on bike performance, you need to appreciate some of the laws of physics. Namely, that a object (w/mass) in motion wants to stay in motion. That answers the question, "Why isn't it easier to "ride" (maintain a constant speed) a light bike than a heavier bike?"
Unfortunately for us earthlings, the laws of physics also say that in order to accelerate a bike (acceleration in physics is a bit different than its usual use because it means both changing speed up AND down) you need to take into account its mass (weight). Heavier bikes take more energy to accelerate than lighter bikes.
It is the second point, that acceleration qualities are different, that make a light bike such a pleasure to ride. You can ride faster, in the sense of making better overall time, on the light bike with less effort (energy).
You should be a politician, while you're not lying it's not really the truth.
let's take an "average" rider that's not a pro and not overweight. a guy that's 170 lbs in his tighty-whities. he's going to be wearing about 5 lbs of gear to cycle including shoes, helmet and clothing. So you got a 175 lb rider.
Now you got your 15 lb bike and your 20 lb bike, but not really because you go riding with 2 bottle of water unless you're an idiot. So we're talking about 48 oz in 2 x 24 oz bottles which is pretty much the norm. That's 3 lbs.
Let's assume our rider never get flats, but if you do, that's another 2 lbs in your saddle bag.
So we've turned our 15 lb bike into an 18 lb bike and our 20 lb bike into a 23 lb bike.
Now we add it up 175 + 18 = 193 lbs for the 15 lb bike and 198 lbs for the 20 lb bike. That's total mass on the hoof which is what counts. The bike doesn't ride by itself.
So the truth is that you looking at 193 vs. 198. So in fact there is only a 2.5% difference.
Unless you are instrumented with a PowerTap or other types of scientific meters, you will not be able to tell a 2.5% difference and even then only on a longer ride where you are comparing data over several runs with 2 types of bikes.
Spending a lot of money makes a lighter bike a pleasure to ride.
Any decent road bike at 20 lbs or under is going to be more than sufficient unless you're a pro.