I’ve been riding for long enough to know that what “feels” good and and what “is” good in terms of technique are two independent sets with a small intersection; it’s very important to put a lot of thought and research into what you’re doing to make sure it offers a benefit. Research takes “work” and “time”, so I’m not very fond of that approach. Instead, I like to do a lot of “thinking”, leveraging both my inadequate expertise in mechanics and my unusually high degree of confidence in my ability to reason in order to jump to conclusions that benefit my initial assumptions.
For example, I believe there is an advantage to riding sur la plaque, or in the big ring, as opposed to riding in the same size gear on the small ring. I generally find that when I’m strong enough to stay on top of my gear, climbing in the big ring feels less cumbersome than when I climb in the small ring at the same speed. The downside is that it is like playing a game of chicken with your legs; it works very well if you are able to keep the gear turning over smoothly, but should you fall behind the gear, and your speed evaporates as you fall into a spiral of downshifting and decreasing speeds (not to mention morale).
All this can be explained away by having good legs or not (un jour sans), but I think there is a mechanical advantage as well.
First, there is the duration of the effort. As they say, it never gets easier, you just go faster, but I firmly believe faster is easier, provided you are strong and fit enough to support the effort. The faster you climb, the less changes in gradient and road surface impact your speed. Not to mention that while all athletes perform the same amount of work when they cross over the same climb regardless of the duration of their effort, athletes doing so in less time suffer for a shorter period of time than do those who go slower. Marco Pantani claimed that despite knowing the suffering that was just around the corner before his attacks, he was motivated to go as fast as possible in order to make the suffering end sooner.
Second, there seems to be a mechanical advantage of riding in the big ring. I’m a little bit hazy on the physics here, but it seems to me that the crank arm is in effect a second-class lever and, while maintaining the same length crank arm (lever) and fulcrum (bottom bracket), by moving into the big ring, you are moving load farther out on the lever, providing a mechanical advantage over the small ring.
WikiPedia defines leverage as:
load arm x load force = effort arm x effort force
In our case, since the speed is constant, that means that the load force (to turn the pedals) is also constant. And, since the load arm (crank) is a fixed length and the effort arm length is increased when moving the chain to the large chainring, the effort force is reduced in order to maintain a balanced equation, meaning that it doesn’t just feel good to ride sur la plaque, it actually is good.
All that said, this theory completely ignores the energy loss of bending the chain as you start to move the chain from straight at the center of the cassette towards the edge of your cassette, in particular when riding in the big ring and crossing to bigger cogs. Q-Factor has an impact on how much your chain is bending as you ride in bigger and bigger cogs, but I think there’s a measurable loss if you are crossing your chain completely (big ring to biggest cog); and I suspect is is entirely possible that the big ring’s mechanical advantages are outweighed by losses in chain friction.
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So moving to a compact drive on my new bike I found that it's more challenging for me to stay on top of the large chainring. On my old bike I was on the large chainring probably 90% of the time, now I'm on it much much less than that. I like the new look of the velominati btw.
@Marko
Hm, interesting...does that conflict with the theory here? I think it might. I would think your big ring, whether or not it's compact, should have an advantage over the small ring, and that a bigger ring is better - provided you can get on top of the gear, so I don't know if what you're feeling is mechanical or some other factor. We really need our resident physicist, Jim, to chime in here.
Are there maybe other factors going on? Are you in the same position relative to the BB? Maybe you're spinning more these days than you did before?
And thanks, re: the site. We're working to get it easier to get to archived content, since readers seem to focus on the most recent post, we've simplified the main layout, showcasing comments and recent, popular, and random posts. I'm glad you like it.
Since I've swapped to a 34/50 compact crank (I'm old) - It's changed my riding style. I now live in the big chainring and only use the 34 for actual climbing.
Old school me cringed at using the big ring/big cassette combo for awhile - but now I don't care. It works without a problem (I'm running 10 speed Ultegra).
With the 50, I find myself going a bit faster and hitting hills a little more aggressively then usual. It's almost turned my bike into an actual "10 speed" with the 34 ring only used as a bail out gear for steep climbs.
At first, I wasn't sure I liked the compact set up, but now after a year or so - I dig it.
@Dan O
I haven't gone compact mostly because I can't get the Record crank in a 177.5 in anything other than the standard fitting. It would be great, though, because it is so easy to pull the cranks, you could swap out if you wanted to.
I have, however, made the plunge to a 25T pie plate in the back (up from my 11-21 block back in the flatland!) and I'm seriously considering a 26T; since the larger cog in the back should offer the same mechanical advantage with regard not to the crank, but to the wheel. I spend lots of time in the ol' 39x25 here in Seattle on these grades!
It could just be that I'm fatter and out of shaper. Thing is though, I'm about 2-3 kph faster on my regular routes than I was on my old bike. But i'm mostly on the small ring. So on the one hand I feel like a huge Nancy and on the other I feel like Thor. As far as fit goes, my new bike is certainly more comfy. Which reminds me, I gotta send in those riding position pics for public scrutiny
@Marko
Well, of course you could be fatter or out of shaper, but that doesn't match up to the 2-3 extra kph's of love you're feeling on the training rides.
I'm wondering if this is less a mechanical advantage thing and more just a change in position and new pedaling style? Is it possible you were pushing gears that were too big on the old bike and now you're just settling into a higher cadence that may work better with your physiology?
I don't think the size ring you're pushing is a reflection of your Nanciness. I think the amount you piss and moan about inclement weather is a reflection on your Nanciness and I don't hear any of that, so we're good. And, your extra kph's are definitely a reflection on your Thorness.
The Dutch seem at once scathing and complimentary. How duplicitous.
@Marko
Ha! And the funny thing is, I thought I was being really supportive. The Dutch are so awesome, we don't even know when we're scathing!
@Marko
Hmmmmm.......you don't know Nancy like I know Nancy. I just got passed by a woman today and she was on a compact crank, she spun by as I was crushing the old 39x26 in a sweaty lather. MF'er.
I rented a carbon Trek with a compact crank in Utah and I dug it, maybe the 39 is holding me back? Or I'm an old weak pussy......I'll let some Dutch guy do the math. I'm afraid to.
Yeah John, I surely would have been passed by her as well or inumerable other Nancy-haters. I'm lucky though, there are only perhaps 15 dedicated cyclists where I live and I'm one of the more fit ones so that doesn't happen to me often. All my Nanciness comes from within.