# General Cycling Discussion - Measuring for Bike Fit

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View Full Version : Measuring for Bike Fit

01-14-09, 08:40 AM
Hi:

I'm looking to purchase a new road bike and am using the instructions here: http://www.rei.com/expertadvice/articles/bike+fit.html

My measurements are as follows:

height: 5'6""
inseam: 29"
arm reach: 22"
torso: 25"

So based on this formula for measuring for top tube length I get the following:

((25+22) / 2) - 6 = 17.5 (inches)

So given that the guide gives 2 inches either way I'm looking ideally a frame with a 20 inch (effective) top tube length? That's the shortest top tube I found for steel road frames I'm looking for (gunnar,salsa,bianchi,jamis,kona). Is this right? If so I guess I have a short reach.

Also my inseam measurements seem to indicate I need a 49cm frame or somewhere around there. I got this by multiplying my inseam length by 0.67. Does this seem right?

Any input in sizing appreciated.

Thanks!

dwilbur3
01-14-09, 09:21 AM
You might look at women's sizes. (Not the bikes specially designed for women, but just those with women's sizes).

01-14-09, 07:04 PM
Hi:

I'm looking to purchase a new road bike and am using the instructions here: http://www.rei.com/expertadvice/articles/bike+fit.html

My measurements are as follows:

height: 5'6""
inseam: 29"
arm reach: 22"
torso: 25"

So based on this formula for measuring for top tube length I get the following:

((25+22) / 2) - 6 = 17.5 (inches)

So given that the guide gives 2 inches either way I'm looking ideally a frame with a 20 inch (effective) top tube length? That's the shortest top tube I found for steel road frames I'm looking for (gunnar,salsa,bianchi,jamis,kona). Is this right? If so I guess I have a short reach.

Also my inseam measurements seem to indicate I need a 49cm frame or somewhere around there. I got this by multiplying my inseam length by 0.67. Does this seem right?

Any input in sizing appreciated.

Thanks!

It doesn't sound right. I'm 5'6" and my inseam is 81cm, yours is around 73. Assuming you measured this right, and I do agree with REI's method for that, you do need a 49 cm frame. Your saddle height should be 80.3 cm (inseam times 1.09) from saddle top to pedal axle with the pedal at the bottom.

My inseam is a lot longer than yours. I measure by cramming the coffee table book right up there, like a saddle with my weight on it. It takes two people. That will change your inseam measurement, and at least make your number comparable to mine.

So I probably have a shorter torso than you, but I use a 52 to 54 cm top tube, around 21 inches, with a 9-cm stem on a road bike. I don't think REI is steering you right here, at least it doesn't sound right.