Going Compact: Standard vs. Compact Cranks
If one were to take a tally of standard cranks vs. compact cranks at any T1 transition area at any triathlon in the country, standard cranks would be the runaway winner. The reason for this is obvious: many top triathlon bike companies stock their bikes with standard cranks.
My Pinarello FT1, on the other hand, came stock with a compact crank which may be a reflection of fact that compact cranks are much more dominant in Europe than in the U.S. The question is what, if any, advantages does one type of crank have over the other?
I’ve seen a few articles and many online forum advice givers try to answer this question. Those in favor of standard cranks typically denounce compact cranks as for “weaker” riders or that one “will lose speed.” Even an article by Triathlete Magazine entitled The Pros and Cons of Going Compact does little more than explain the physical differences and changes that may occur on your bike. The article completely fails to address any differences in top-end speed (other than saying you’ll lose some) and likens going to a compact as a halfway house to a triple crank.
Of all the articles I’ve seen, the only one backed up by actual testing is an article by Slowtwitch.com. The Slowtwich article lists a few general benefits of going compact, including:
- Easier climbing. The smaller gear ratios make it easier to climb.
- Reduced weight. The compact crank weighs less than the standard crank and you can get maintain similar climbing with a smaller, lighter cassette (e.g. an 11-23) versus needing to carry a 12-25 or a 12-27 with a standard crank.
- Closer gear ratios. Closely related to the previous two items, the larger your cassette span is the more your gears are spaced out. A standard 12-25, for instance, has a gear ratio of: 12-13-14-15-16-17-19-21-23-25. A 12-23, on the other hand, has a gear ratio of 12-13-14-15-16-17-18-19-21-23. On the 12-25 cassette you are skipping the 18 cog in exchange for the 25 with the result that the biggest 5 cogs in the cassette all skip at least one tooth. Not that big of a deal except when you’re looking for a very minor change in gearing.
- Reduced knee stress. Pushing the big crank is hard on knees, but the compact crank reduces this stress a bit. This was one of the biggest reasons I chose the Pinarello over the Cervelo P3: my knees (old football/wrestling injuries) hurt on the P3 from about two minutes into the ride whereas they rarely hurt on my compact.
- With the smallest cassette (11-21) on both the compact and the standard, the top end speed on the standard crank was higher: 33.2 MPH vs. 31.3.
- With a 12-25 on the standard crank (very common stock setup) and a 11-23 on the compact crank, the top-end speed on the compact is actually faster: 31.3 MPH vs. 30.42.
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