Step 1. Measure Yourself Up.
You wouldn't go to buy a suit or a dress without knowing your size.
Similarly, it is useless to start looking for a bike if you don't know what size you need.
Bikes are typically (except in the UK) measured in metric, Centimetres (cm) and millimetres (mm). So get used to it. (if you only have a metric tape measure 1 inch = 2.54cm)
Bike Fits can be quite elaborate. Some want you to measure your femur, your tibia, your inseam, your shoulder width....
But the most basic "driver" of Bike Fit is.... you inseam.
Inseam determines saddle height. and the correct saddle height is necessary for comfort (no knee pain) and efficiency (power).
And Inseam is not what's stamped on the tag of your Levis. but your "real" inseam. Barefoot, from the floor to you pelvic bone. That's called your PBH Pelvic Bone Height
Similarly, it is useless to start looking for a bike if you don't know what size you need.
Bikes are typically (except in the UK) measured in metric, Centimetres (cm) and millimetres (mm). So get used to it. (if you only have a metric tape measure 1 inch = 2.54cm)
Bike Fits can be quite elaborate. Some want you to measure your femur, your tibia, your inseam, your shoulder width....
But the most basic "driver" of Bike Fit is.... you inseam.
Inseam determines saddle height. and the correct saddle height is necessary for comfort (no knee pain) and efficiency (power).
And Inseam is not what's stamped on the tag of your Levis. but your "real" inseam. Barefoot, from the floor to you pelvic bone. That's called your PBH Pelvic Bone Height
So, barefoot, feet slightly apart, then jam something rigid (like a thin book) between you legs and raise it to it til you hit your pelvic bone. (a second pair of hands is helpful here. get a helper) You'll feel it. Be aggressive. Bang it.
Then step away from the wall and mark (masking tape?) that height.
That's called your PBH Pelvic Bone Height
Then step away from the wall and mark (masking tape?) that height.
That's called your PBH Pelvic Bone Height
- Measure your inseam (see below, and it is not the number marked on the back of your jeans)
- "Ideal" Frame size = 67% x Inseam/PBH.
- "Ideal" Saddle Height = 88.3% x Inseam/PBH
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To get your inseam/PBH:
1. Stand back to a wall with your bare feet slightly apart. 2. Stick a rigid T-square (a thin hard cover book works well) between your legs and jam it up as high as you can, til it hits bone. ( a helper is helpful here) 3. Keeping the T-square in place, step away from the wall and mark this spot on the wall. 4. Repeat 2 or 3 times to get a good average. This is your inseam. Most bike dimensions are in metric, so to convert your Imperial (inches) multiply by 2.54x. Briefly, your ideal frame size is about 67% of this measurement (this is known as the "Lemond System" (developed by champion rider Greg Lemond). Slightly bigger (add 1-2cm) for a casual recreational riding frame (so you'll feel less hunched over.) Saddle Height Arguably, saddle height (from the middle of the bottom bracket spindle to the top of the saddle) is more important than actual frame size. I ride folding bikes which have weird pint sized frames that do not resemble any normal bike frame. To compensate for the compact frame size, they have crazy long seat tubes. But as long as my seat is set to the right height (82cm) and my handle bars are at the right height (though handlebar height is less important that saddle/seat heigh as the legs and knees are doing all the real work) I am comfortable. Lemond advocates a Saddle Height of 0.883x your inseam or PBH. I for instance have an inseam of 93cm and Lemond's system recommends a frame of about 62cm and a saddle height of 82cm. There are however alternative views on Frame Sizing. Recently there seems to have been a move to more compact frame sizes, down 2-4 cm (and would have me on a 58 or 60cm frame.) |
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