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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@frank
Basically, the smaller the Chainring, the less opposing turning force there is against you pedaling
BUT in order to keep the gear ratio the same the cog will have to be smaller, which will be creating less turning force. So the change in size of the chainring and cassette cancel each other out.
@david
I posted that article in here primarily for the technical data, not the dude's assesment. That said, my assesment of the tech data underscores that it's really so dependant on the cassette that all this back and forth about the chainrings is a bit like hitting our heads against the wall, again and again and again
Well, I appreciate what the article is saying, and I would say it just depends.
Where I ride it is mostly rollers, all over. Hill after hill after hill. We big ring everything because it maintains momentum, and once over the hill you recoop so much momentum so much faster it really is significant. Our hills though range from 1/2k to 2-3k at the longest, up from 100m to 300m at the most. They are just short intervals. That said, I can beat and out run most compacts given the same routes and all because of the length of the gear. And forget triples, I just don't like them at all.
I don't agree that big ringing the Alp's however is better. The long mtn pass's that go on really require one to find a cadence and spin that is optimized for it. Big ringing isn't it til descending.
@Marko
Well, the back and forth on chain rings (at least for me) has to do more with mechanical advantage than speeds and cadences, which is what the data you provided speaks to.
To me, it definitely feels better to ride the same size gear in the big ring versus the little ring.
@Nathan Edwards
But that doesn't take into account the considerably bigger diameter and angular momentum of the wheel, not to mention that the diameter (and then also the leverage from the cog) is relatively much smaller between the 16 and 21 (for example) that you would be switching between when riding roughly the same size gear in the big vs. small ring. Whereas on the crank set, you're looking at something closer to a 1/3 bigger diameter/more leverage.
@Souleur
Aside from the weight and aesthetic concerns associated with triples, I've found it incredibly hard to maintain shifting quality with a triple because the rear dérailleur just can't accommodate the changes in chain tension between the rings. Then you start looking at medium or long-cage dérailleurs and I don't think we even want to start that discussion.
@brett
so it's the taller people who are forced by manufacturers false assumption of physiology into buying bikes with cranks that are too long for them?
I appreciate the science that smaller gears are lighter and by customising your gearing should give you equivalent gearing. So in that respect are better.
It certainly doesn't equate in practice, especially for racing cyclists.
Anyway, this has been a fascinating discussion and I will leave it with the fact that compacts are wank and have no place in the Velominati.
@frank
Oh but it does. The difference in Chainring is cancelled out by the difference in cog.
@Jarvis, @brett
Crank length based on frame size is as good an assumption to make as any, but it's something that the rider/bike fitter should definitely take into account and have the option to swap out for their optimal length.
Brett, I have to say I'm puzzled by the choices that Specialized has for crankset types - the Tarmac gets a standard while the Roubaix has the compact? With the Tarmac being the better climber, I'd definitely expect those to be the other way around. Any thoughts on why they went that route?
I'm late to the conversation, but I'll relate my own experience. For years, I was on a 52/42. Moved to a 53/39 on my Colnago in '96 and realized climbing seated was nicer on my knees, less energy wasted and my speed increased. Bought a cross bike in '06 to also use as a commuter and found that the supplied 46/36 sucked as I was spinning out all the time. I like to pedal down hills, and found I couldn't. So I bumped to a 50/34 compact. Still had a 53/39 on my nice bike and just adjusted to whatever I was riding that day. The compact was great when pulling 2 kids in a trailer (over 100 pounds) up 15% hills. HTFU!
Curretly (and sadly) a one bike guy for the first time in 20 plus years, and I've got a 50/34. Last year when the car snapped my tibia and fibula, I needed a compact to spin the easiest gears possbile. I'm making due this season with the one bike, and finding that as my legs have come around I'm not using the easiest gears. I do most of my climbing in the 19, and will move up if I'm riding the steep stuff. I say if you adhere to rule #5, you will choose the gear that makes you fastest. We all know if you have the legs, nothing else matters. I'd be happy to invite anyone to Portland for a hilly ride that includes plenty of 20% or more hills. A compact can be handy at times. And I can pedal up to 45 mph going down in the 50/11. That said, I don't know if I'll do compact or standard on the nice bike that I'll be getting over the winter. The aesthetics issue isn't bad for me as I'm on a 50cm bike with 170's. The compact looks fairly "normal". I feel like I'll have a better idea of which direction to go after this season. A compact on a 15 pound bike might be overkill.
On a side note, my best to all who are doing the Tour de Blast tomorrow. You'll have a great time. It can be very different weather on top, so be prepared.