Rule #14

[roydyates]

Almost every rider I know has a road bike whose size is within a centimeter of

"Your height in inches" - 14.

For example, I'm 6 foot 1.5 inches = 73.5 inches.

73.5-14=59.5. I have 4 bikes that are 60cm and 3 bikes that are 59cm.

The biggest exception I've heard about is Shawn Bradley. From the Shawn's stolen bike thread, I learned his bike is 80cm, but his height is 7 ft 6.5in = 90.5in. The rule of 14 says he should be riding a 76 or 77.

So, I'm wondering how often is the rule of 14 wrong. How many people around here are exceptions? If I had to guess, the exceptions here will be young guys with the flexibility to ride small frames with slammed stems.

[chuckroast]

No exception here. 5'-11", ride 56 and 57's.

[fjaws]

I'm your height.... 57cm Serotta, 56 Cervelo, 56 Van Dessel.

[ergott]

Too big for me. I ride 53-54 (even some 52s) and that formula gets me a 55 (5'9").

[fourflys]

68", ride a 54 to a 54.5 top tube...

[e-RICHIE]

Originally Posted by roydyates

So, I'm wondering how often is the rule of 14 wrong.

it's wrong atmo -
you cannot determine the frame measurements and contact points without using leg length and foot length.
a rider's height is completely irrelevant.

ps

arrange disorder

[tannhauser]

What does size even mean? ST or TT? If it's ST then the rule is off by a factor of a million for me.

[Kirk Pacenti]

As a rule of thumb it could be a useful starting point for test riding an off the peg bike. But I would hardly recommend it as a way to determine your proper size.

At 72" tall, it happens to work for me. Most of my bikes are 58cm c-t-c. Though I have always preferred bikes that would be considered on the large size for someone my height, compared to what most shops would recommend, (usually 56cm).

I have heard it expressed another way that yields similar results; your height in feet and inches, minus two... i.e. 5'-9" = 57cm. ymmv. Of course all bets are off if you're considering a compact frame design.



Cheers,
KP

[Louis]

My numbers:

6 x 12 - 14 = 58

Off the peg I ride 60 ST, custom I ride 61 ST

Explanation: my legs are long compared to my torso length.

Rules-of-thumb are good for average ratios, but fail at the tails of the normal distribution.

[ergott]

Originally Posted by Kirk Pacenti

I have heard it expressed another way that yields similar results; your height in feet and inches, minus two... i.e. 5'-9" = 57cm. ymmv.


Cheers,
KP

Yikes. Me on a 57cm would be a bad idea.

[Frankwurst]

I'm 70 and have 2-56's, 1-58, and 1-59 right now but none of them are square.

[roydyates]

Originally Posted by e-RICHIE

it's wrong atmo -
you cannot determine the frame measurements and contact points without using leg length and foot length.
a rider's height is completely irrelevant.

ps

arrange disorder

As others point out, one number hardly describes the size of a bike just you observe that one number hardly describes the size of a person. Perhaps one number for a bike frame is even less precise since we all agree on how to measure the height of a person but there are a bunch of ways to measure the size of a frame.

The fact that it's wrong but in the right ballpark makes it more interesting to me.

[tannhauser]

It's not even close.

[roydyates]

Originally Posted by Kirk Pacenti

As a rule of thumb it could be a useful starting point for test riding an off the peg bike. But I would hardly recommend it as a way to determine your proper size.

At 72" tall, it happens to work for me. Most of my bikes are 58cm c-t-c. Though I have always preferred bikes that would be considered on the large size for someone my height, compared to what most shops would recommend, (usually 56cm).

I have heard it expressed another way that yields similar results; your height in feet and inches, minus two... i.e. 5'-9" = 57cm. ymmv. Of course all bets are off if you're considering a compact frame design.

Cheers,
KP

5' 9" =57cm is an even goofier rule since there is a nonlinear mapping of inches of height to cm of bike size. That is, 12 inches in a foot adds 10 cm but each inch in the inches category adds a whole cm.

[e-RICHIE]

Originally Posted by roydyates

As others point out, one number hardly describes the size of a bike just you observe that one number hardly describes the size of a person. Perhaps one number for a bike frame is even less precise since we all agree on how to measure the height of a person but there are a bunch of ways to measure the size of a frame.

The fact that it's wrong but in the right ballpark makes it more interesting to me.

there was a time, not too long ago, when the industry standard to see if a bicycle
would be in the ballpark for a user consisted of the words, "stand over this". that,
too worked well for the masses atmo.

ps

arrange disorder