Originally Posted by
Bacciagalupe
Does weight matter?
I say: No and yes.
"No" in that weight will have a minimal effect on the general rider, especially one who doesn't care about performance. Also, in terms of our discussion, "no" in that folding and non-folding bikes are usually very close in terms of weight anyway.
"Yes" in two senses. One in that for an elite handful (specifically, pro racers), 3 seconds at the end of a 40 mile time trial can be the difference between 1st place and 20th. Two in that if you have to carry the bike up a flight of stairs or onto mass transit, a lighter bike is much more convenient.
At the risk of a bit of repetition: the primary issue, which I think you're starting to understand, is that weight only matters when you're accelerating. Once you have achieved a specific velocity, though, the force that will slow you down is friction: drag (which is the largest factor), rolling resistance and drive train efficiency.
The trick is, you aren't spending a lot of time accelerating, and the effects of 10 pounds to a system that totals, say, 150 - 280 pounds is small to begin with. Most of the time you're trying to maintain a certain speed.
This is why you can have strong and consistent subjective experiences that a heavy bike is slow (because it doesn't accelerate quite as fast) or that small-wheeled bikes are more fun (because they do accelerate faster, and that can be more pleasant). However when you add everything up, because you spend so much time at a more or less constant speed and fighting drag rather than gravity, the slower acceleration actually winds up being less significant than it feels.
I think weight is more important for the general rider who doesn't care about performance, because this is the rider that would be content coasting after accelerating. So whatever portion of the effort pie acceleration is for the performance cyclist gets multiplied to as much as 100% for the general rider and the affect of weight gets multiplied along with it. Of course, not every general rider will simply coast after accelerating, but in my opinion most riders spend much more time accelerating than they do maintaining a certain speed. Racers don't, but riders on streets with stop signs, lights, and other traffic do and although it all depends on where you're riding and how far you're going, let's face it, a bicycle is a vehicle much better suited to short trips in dense environments then brevets. That's why the winner of the TDF gets fame and prestige, while the guy delivering chinese food by bike or the guy that drives his car 200 miles to work everyday gets squat.
I would also contend that folding and nonfolding bikes are close in terms of weight because they are too close in terms of wheel size. In my opinion, the conclusion we should draw is that smaller diameter wheels are better because they have few inherent disadvantages and can be made lighter. If 20" wheels are not making a notable difference it's because they're still too large, not because weight doesn't matter.
Originally Posted by
Bacciagalupe
By the way, drag has an impact at all speeds. It's the biggest opposing force you're dealing with as a cyclist. It is more significant for riders with higher power outputs (or, to be specific, higher power-to-weight ratios) because they are riding faster. However, drag is still far, far more important than weight even at slower speeds. [FYI the Kreuzotter does account for this, as you can modify the rider's power output.]
As to objective measurements: A HRM does objectively measure the rider's exertion. However, this is not necessarily going to be a consistent factor, because your cardiovascular abilities can change from day to day -- especially if you happen to be training. I think you'd need a pretty large pool of samples to try and correct for this.
The reason why a power meter will be more objective in terms of measuring a bicycle's performance is that it precisely measures power output, which is what is propelling the bike. It doesn't matter if it's a pro or an amateur or a robot, 200 watts is 200 watts is 200 watts.
So if you know that Bike 1 travels at 15mph when the rider applies 200 watts of power, and Bike 2 travels at 16mph at 200 watts, and the environmental conditions are consistent between tests, you will know exactly which bike performs better and by how much.
To be clear Kreuzotter does not account for weight because, although you can modify the rider's power output, you can't simulate how much operating at a given level of power output will fatigue the muscles, in turn, reducing the rider's power output. There's no feedback. It is assumed that the muscles are a perfect power source whose internal losses are independent of the load, which is false.
You see, 200 watts is not 200 watts is not 200 watts. 200W evenly delivered over one second is not the same as 200 million watts delivered for a millionth of a second followed by nothing for the rest of the second is not the same as delivering nothing until the last millionth of a second and then delivering 200 million watts. Although they're all 200 watts, the first one would have the lowest losses, the second would have internal losses so high they'd destroy your leg just as you started, and the third would allow you to cover ground with your previous momentum before destroying your leg.
Accelerating a large mass has the effect of creating exactly this sort of uneveness. When your muscles have to work harder to accelerate a larger mass they get hotter, more fatigued, and waste more energy to deliver more power now and they don't get that waste back by delivering less power maintaining speed later on. That's why lifting a box and putting it back down is hard work, even though the average power delivered to the box is 0 watts!
Muscular efficiency is generally quoted as being only around 15% and can be as low as 0%. So while I may be able to funnel 200W out of 1000W of total exertion while riding a 15 pound bike, all but 1W may be lost while exerting 1000W to try and push a mac truck. The question is, what about a 20 pound bike, or a 30 pound bike? How many watts get delivered to the pedals for a given exertion?
The thing that makes it so difficult for me to ignore subjective rider opinion of exertion is that it's the only frequent recorded measurement of what is obviously the overwhelmingly largest mechanism of loss. Things like rolling resistance, aerodynamics, and friction are generally quoted at maybe 10-20% total, but when it comes to the biomechanical losses we're talking 75% or more. So the subjective observations would have to be really way off to reverse the conclusion...which begs the question if there's a total disconnect between the feeling of exertion and actual exertion then shouldn't we be more concerned with the feeling of exertion anyway? After all, the feeling is the basis of your decision to push yourself harder, or to stop riding, or to continue that long commute. So shouldn't that be the important parameter?
Originally Posted by
Bacciagalupe
So the myth that "you have to pedal more" or "smaller wheels must be slower" are incorrect, while "smaller wheels are harsher" is true specifically when you are comparing equivalent tire types.
Yeah, but that depends on whether the heavier larger diameter tires can really be called equivalent (which I believe we still haven't settled). If heavier wheels are worse then the equivalent tires would need to be skinnier, thus, pushing us towards parity of harshness.