Regular blog readers know I'm working on a book chapter on bike fit. When I wrote the first edition of The Female Cyclist (published in 1999), I used anthropometric data available from the U.S. military. Using this original data set, the major fit concerns (given a male and female of equal leg lengths) were arm reach to the hoods or drops, and hand size.
As an example, let's compare data for females and males with 65-inch leg length. With equal leg lengths, the data showed that arm length for women was, on average, shorter by two inches. In addition to shorter arms, these sample women tended to have hands that were 0.7 inches smaller than the sample men's hand. One thing to note when thinking about bike fit is how this data would affect reach to the brake levers and gripping ability.
Comparing these women and men of equal leg lengths, the proportions put the men at 66 inches tall and the women at 64 inches tall. While overall height is different by two inches, these sample riders have torso lengths within .1 inch of each other—very close.
This data worked well when examining bike fit. However, the average male in the original data set used was 69 inches compared to the average female at 64 inches—a five-inch difference. When The Female Cyclist was written, most bicycles were manufactured to meet the needs of the average cyclist—that being an average-sized male.
Since that time, some fantastic changes have taken place. The multisport and cycling population has grown, creating a demand for recreational and high-performance bicycles for people of all sizes. Because equipment is available to make cycling more comfortable, more people are attracted to the sport. This is an excellent synergistic relationship.
Notice in the discussion about average male and female dimensions in previous paragraphs that I use the phrase "original data set." I am now in the process of reexamining anthropometric data using "The Measure of Man & Woman," published in 2002. What I found in this more recent collection of data is that the difference between the average U.S. male and female, in the critical dimensions affecting bicycle fit, is very small. Proportional to height, the male and female dimensions of leg length, hand length and arm length are very close in this more recent data set.
While U.S. men are, on average, five inches taller than women; the proportions of the two groups are very similar. Of more concern to bike fit than male-versus-female proportions is ethnic background. For example, the average Japanese male has a seated height (measured seat to the top of the head) equal to the average U.S. male. From that same seated position, however, the Japanese male has a leg length 3.6 inches shorter than the average U.S. male. This is a significant difference and has a major affect on bike fit.
Triathlon Bikes are Gender Blind
I was discussing the issue of bike fit and design with Paul Thomas, the North American sales vice president for Kuota bikes. I asked him, "Why do companies market bicycles to males and females when this strategy shuts men who happen to be shorter than average out of the smaller bicycles marketed to women? How many men do you think will purchase a women-specific design, even if it fits them better than the men's bike?"
He came back with an interesting comment (one I wish I could take credit for). He said Kuota and other companies that manufacture tri-specific bikes have never gone after a women-specific design versus a men-specific design. They have simply provided a wide range of frame sizes, small to large, to fit average males and average females in the sport. Frame dimensions have more to do with performance than gender.
If you look at the range of sizes offered in triathlon-specific bikes at your local shop—from entry-level rides to the hard-core tri bikes—you will find a wide range of sizes. Bike selection in the triathlon market tends to ignore gender in favor of proper fit and performance.
Unfortunately in the road-bike market, some of the guys that would fit better on a women-specific road bike won't get that great fit because of marketing and image issues.
New Bike Dimensions and Fit
It is absolutely critical that you are properly fitted to a bike that fits you. Sacrificing fit means sacrificing performance and will possibly put you at risk for an injury.
It is nice to have anthropometric data and a look at the averages for our population. This can give you a general guideline as to what to look for when choosing a bike. However, you need to find a bike that fits your frame—not try to force your frame to fit a particular bike.
If you were born with a shorter-than-average torso, then a bike frame that has a shorter top tube will fit you better. Something else to consider is your flexibility. Due to limited flexibility, rather than a short torso, you may need a frame with a shorter top tube—something to consider when looking at different manufacturers.
On the other end of the scale, if your genetic history gave you a long torso or proportionally long arms, look for manufacturers that have longer top tubes relative to the seat tube length.
When shopping for that new bike, work with a store that is willing to work with you. Give your business to the staff that is interested in getting you on the bike that fits you the best.