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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@Nathan Edwards
Love the Boardman. One of my favorite riders to ever turn a gear in anger. I loved his assault on the hour record, and then his subsequent realization of technology taking over and playing a more important role than the athlete. (He is a cycling gear head and would put any of us to shame. There's a great piece on him in Rouleur.)
He petitioned the UCI to introduce the Athletes Hour and then proceeded to break it. Amazing guy.
I believe Big Ring Girl Nicole Cooke won both the Olympic and World Championship road races aboard a Boardman. He had a crazy long back, and his frames seem to have a really long top tube. Very cool bikes.
Well done, mate.
One other thing to keep in mind, however, is that being overgeared is also bad. Despite the physics, you have to match your gearing to your ability to turn it. I have gradually been shifting to lower gears, and my speeds increase on the steepest slopes. For more on that, just watch Basso and Evans on the Zoncolan.
In my case, fairly slowly.
I met him when he was racing. Very sound bloke indeed and a legend over here.
The Boardman bikes are remarkable value and really quite impressive.
@frank
If the crank arms are the same length, then there is the same leverage. A 175 on standard rings and a 175 on a compact has the same leverage.
A smaller ring means there is less friction, not more. Look at the pic at the top of the page, there is huge contact of chain and ring, therefrore more friction.
There is also less rotating mass with a compact, so there is less resistance too.
The article Marko sourced is here:
http://www.slowtwitch.com/mainheadings/techctr/gearing.html
@brett
you beat me to the punch.
@frank
Hopefully it will bring me some success, after destroying myself on a 300 mile (why the heck did I do one of those) cyclosportive last weekend, I've got to look ahead to two criteriums this coming weekend and the British Unis track championships (I've never ridden a track bike :S)
@guycollier
I distinctly remember back at the age of approximately 10 (so the year Lance won his second Tour), the days I still believed Boardman could win the Tour. My Father didn't bother to dispel the idea. Anyway, I distinctly remember when on holiday in the lake district, walking somewhere, and seeing a cyclist in full Credit Agricole kit coming the other way, who greeted us with a polite good afternoon. Myself and my Mum both being little versed in velominati-ness looked at the rider and the kit. My Dad of course looked at the bike, and said he hadn't seen the rider. Anyway a discussion ensued, the conclusion being that we had just seen Chris Boardman :)
Oh for the naïve days of youth.
@frank
leverage, that's the monkey. bang on the me
@brett
but crank length is important to correct positioning on the bike. And being able to pick and choose cranklength is fine for those deep-of-pocket or in the trade, but most bikes that have compacts are not sold with optimal performance in mind but with ratios that are lower to get up hills easier without the need for the weight penalty of a triple and with longer cranks to allow more leverage to get up hills more easily.
I run 172.5, but compact's generally come in 175. Now this next bit might be an old-wives tale - I am no physcist - but the longer the crank the more leverage and so the longer it takes to turn the crank. Fine for getting up hills more easily, but not so good for jumping on the wheel of the guy's who has attacked down the opposite gutter.
Also, if compacts are lighter and have a better range of gearing as that slowtwitch article suggests, then why don't the all the PRO's use them in races as well as for training?
@Jarvis
I'm gonna have to do some sums now...
Basically, if we model it physically, the friction/resistance forces aren't going to change much between the two. So all that matters is moments (leverage). I'll do some sums.
Btw, I think the cranks on my new Boardman are 172.5 anyway.