Metric or Inches: Can the Bike Industry Make Up Its Mind?

I can't help but notice that there seems to be no particular standards for weights and measures when it comes to bicycles.

Most bicycle references in the magazines are metric, but even so, a stem will be 150-millimeters and the fork steerers it is supposed to fit are stated in fractional and decimal inches—like 1.5" and 1 1/8 inches. I read weights in pounds, ounces, kilograms, grams. Can't the industry just settle on one form of measurement?

—Gilbert S., Miami, Florida

I was in Switzerland, riding with DT/Swiss and Schwalbe. The group spoke many languages: Flemish, French, Dutch, Italian, Swiss/German, Portuguese, Spanish and English. We settled on English most of the time, so that nobody was excluded from the conversations.

I became keenly aware that a great percentage of English words were derived from other languages, and more so—because I (ashamedly) do not speak a second language fluently—how cycling has become a language in itself. Cycling's jargon, after all, is a mixture of English, French and Italian.

As long as we were discussing cycling, we could hang with the conversation in spite of language barriers. It was like: "Schwalbe blah blah blah, 25-centimeter clincher blah blah 9-Bar pressure blah blah, three rubber durometer tread." Like English, cycling-speak is a composite language.

I realized then that I could go into a bike shop in Germany and order a 700C, 23-millimeter Schwalbe Ultremo tire for my road bike and a 1.35-inch Kenda Nevegal for my mountain bike and the clerk would understand exactly what I wanted. That same German clerk could buy a Reynolds carbon fiber fork with a 1/18-inch steerer tube in the U.S.A.

Mixing languages, measurements and weight standards is how the living culture of cycling operates, and it allows an international sports community to buy, sell and communicate with each other. So far, it works pretty well, and although it has its quirks, the language of cycling has proven to adapt quickly to emerging technology and trends.

My advice is to relax with it. Look past the numeric values of the inch and metric systems, put away the conversion calculator and adapt the numbers to mean "longer" or "shorter," "heavier" or "lighter" so they can become useful words in your everyday cycling language.

700C is a road bike wheel. A 15-centimeter stem is longer than a 10-centimeter one. A 1 1/8-inch steerer needs a 1 1/8-inch headset. If we employ the disparate measuring standards of bicycle culture in a relative sense, they become transparent, and we communicate clearly.


There are a number of reasons for the mixing of metric and imperial weights and measures. For instance: Ever wonder how the 27.2-millimeter seatpost came into existence? Why not an even 27? It's because metal tubing is drawn to international inch standards in order to insure that a tube purchased from France will support the same loads as one bought in Japan or the USA, and that tube A will slide into socket B throughout the world. The 27.2-millimeter post is a perfect slip fit into a standard 1 1/8 inch steel tube with a .028-inch wall thickness.

Isn't it odd that a 31.8-millimeter derailleur clamp fits a 1 1/4-inch-diameter tube?  For the same reasons, wire gauges and the diameter of balls inside of ball bearings, metric or otherwise, are produced in inch-based standards.

The four most popular frame sizes (54, 56, 58 and 60-centimeters) are duplicates of the once-dominant inch-standard sizes (21, 22, 23, 24-inches), rounded to the nearest centimeter.

In the bicycle industry, however, all of these dimensions are expressed in metric increments. The reason for this is all about communication. Almost every bicycle made is produced in a country where the metric system is used exclusively. Because the bicycle business is international, it makes sense to communicate in the numerical language that is fluently spoken in all but three countries.

That said, long-standing inch standards persist, even in France, where great care is taken to erase all evidence of foreign influence. Steerer tubes and headsets are universally expressed in inches, and the roller chain and sprockets that have driven the bicycle since the dawn of cycling are 1/2-inch-pitch-exactly 0.5 inches from pin to pin.

It would seem that cyclists are doomed to live as stepchildren of the inch system for the foreseeable future. Consider it to be a cyclist's secret handshake.

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