Mountain Bike Sizing for Dummies

bicycle frame components

We've noticed over the years that even the supposedly vetted freelancers for the "specialized" sites of eHow.com weren't always particularly trustworthy. Sometimes it was because they were just plain... stupid... but we'll admit that most of the time it was because the freelancers wouldn't stay in their lane. Take, for instance, "ACE-certified personal trainer and certified RRCA running coach" Deborah Dunham: she (probably) knew what she was talking about when it came to her areas of specialization, but our cyclists say Deb had no business trying to write, "How to Measure Mountain Bike Frame Sizes."

Some of the deficiencies in Durham's article stem from changes in the MTB world in the decade since she wrote this. Part, but not all: we refuse to believe that someone who repeatedly mentions "the distance of the seat tube" knows anything about bicycles, either road or MTB; but say it Deborah did:

Mountain bikes are generally measured by the distance of the seat tube, which is the vertical part of the triangle the frame forms. The tube runs from the bottom of the seat post where it meets the top tube to the middle of the crank.

Other than calling the length of the seat tube the "distance," that's nominally correct¹. Once she gets past that, however, she's in trouble...

• "The seat post is the short stem that holds the bike seat." – In some MTB configurations, the seat post is longer than the seat tube!
• "The top tube is the horizontal bar that runs along the top of the bike..." – Few, it any, MTB top tubes are "horizontal." Deb's thinking of 1970s road bikes, we guess.
• "...the crank is the larger circular piece in the middle of the bike where the pedals are attached." Uh, no, that's the chainwheel. And the pedals aren't attached to the "circular piece," they're at the ends of the crank arms. 

Dunham also has some weird ideas about how this whole thing works, exhorting her readers to,

"...use a tape measure to determine the distance [sic] of the seat tube... Compare this measurement with the one listed for the mountain bike you are previewing."

Ummm, is she trying to say that you may get a different measurement than the specs? Really? ANd then there's,

"Know the top tube measurement. This is the distance from the bike post to the handlebars and determines your reach."

Errr, what is a "bike post"? FWIW, Deb, the top tube length is from the seat tube to the head tube... Dunham completed her exposé of MTB sizes by warbling that,

"The most common mountain bike frames come in 15-inch, 17-inch and 19-inch sizes, and generally they are listed as small, medium, large or extra large."

She can't even count: 15, 17, 19 vs. S, M, L, XL? It does not compute! Combine that dumbassery with her obvious ignorance of bicycle terminology, and ladies and gentlemen, you have a Dumbass of the Day! We mean, she never even mentioned standover height!

¹ In reality, seat tube length runs from the underside of the top tube to the bottom bracket, not from "the bottom of the seat post."

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