45 Chainring - part 2 (of 45?) - Road Cycling UK

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45 Chainring – part 2 (of 45?)

My, they really are modest

Even though fitting a 45 tooth outer chainring was RH’s idea, somehow its usefulness really struck a chord. Essentially, my previous article argued that, by using this size ring,  more time could be spent in the big ring and, as a consequence,  more time therefore spent in the central sprockets of the cassette, thus creating a straight, efficient chain run more suited to everyday cycling needs as opposed to those imposed in a competitive environment. Now, however, I would argue that even in the racing arena the humble 45 has its place.

For some, the simple idea that smaller is better sits uncomfortably with the heroic, muscular image that cycle racing  conjures, yet the essence of cycling achievement is speed, plain and simple. Pushing a big gear doesn’t equate to speed, although the ability to  “out-gun the opposition in every gear” will undoubtedly win races and set records. The difference lies in the choice of gears and, crucially ,one’s cadence.

Every cyclist knows what gear they’re using and how that gear affects their cadence, but how many of us know what that cadence is? A rough guide will tell you that 60-70 revolutions per minute is low, 80-90 is an optimum and 100+ is high. Yet for many stomping on the pedals in a big gear resembles speed whatever the revs. However, use of a modest outer chain ring can keep the chain centrally aligned in all but the most taxing circumstances yet still achieve impressive speeds.

Take a training/pleasure ride over 25miles; let’s say you wish to achieve an average of approximately 18 mph. That equates to using, at around 90 rpm ratios of 45×18, 53×21 or 50×20. Allowing for changes up or down the cassette, the 45 would seem the best choice. It would require doing the same ride at an average of approx 23mph before the larger chain rings allow central placement on the cassette. In this case ratios of 45×14, 53×17 or 50×16 are needed.

Averaging around 23 mph constitutes fairly rapid riding and a reasonably high cadence, something I would argue is outside the parameters required by the average commuter/ sportive rider. However, as most of us use the larger chainsets and are more comfortable with speeds nearer the 18mph average, a gear of 50×16 at 70rpm would achieve a combination of the above scenarios.

Taking this argument to its extreme one might like to consider that, when Chris Boardman broke the Eddy Merckx athlete’s hour record, he used a gear of 54×14, about 104 inches, and his average cadence was 99 rpm. A combination of reasonably high cadence and high gears, yet still his choice only equates to 46×12 approximately.  Admittedly the smooth running of his choice of gearing far better suits a track environment but this comparison shows the speed potential of the “smaller” big ring.


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