Framebuilders - How do I size my stem?
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12-05-08, 01:54 PM
I'm building up a bike form an old Schwinn Super Sport and need a new stem. I was going to get a Nitto Technomic stem but I'm not sure how to determine the proper reach.
Is there some metric I can apply to the frame and my body that would get me close to being able to order the right size? I'm going to have to widdle the thing down a little in order to fit it into the 21.1 mm headset on the Scwhinn so it's kind of critical to get the right size.
You can look at it two ways, what is proportional to the frame, and what is the right size of stem for you for the best possible fit whether the frame is the right size or not. Would help to know what size of frame it is, though personally I don't know the bike you are speaking of so I couldn't take it further.
12-05-08, 09:27 PM
Basic rule of thumb is thus:
- adjust your saddle up and back until you are pretty close to KOP (do a search if you don't know what KOP is)
- pick a stem to allow you the amount of "lay out" you desire. Sporting riders like to stretch out more than cruisers. Let your back be your guide.
Racer types typically pick a stem that will allow their elbows to clear their knees while pedaling in the drops with a flat back. Tourist types often have "overlap" of their knees to elbows, but these folks rarely get low enough for this to matter.
here's a handy trick for measuring the inner diameters of things... get some heavy paper or card stock, carefully roll it up squarely upon itself (make a perfect cylinder, not a cone) stick it into the section of frame in question, and mark with a pen where the paper doubles over on itself... then lay it out flat and measure the distance from the edge to your pen mark... divide the measurement by pi and you have your diameter... i find this to be more accurate than eyeballing a ruler over the hole to approximate the diameter.
KOP (do a search if you don't know what KOP is)
does this have to be an acronym? knees over pedals.
here's a handy trick for measuring the inner diameters of things...
the same trick works for measuring the outside of things too. It helps to have a squared off sheet of paper so you can line up the edge of the paper up with itself.
Calipers are nice too.
calipers sure are the 'right' tool for the job, but yeah, card stock or paper & measuring tape are things people generally have handy.
12-19-08, 03:10 PM
i used paper and string for setting up bikes for a long time. it's how my dad showed me. but these days harbor freight sells vernier calipers for $1.99 that are accurate to a tenth of a mm, and they are so inexpensive i don't hesitate to let teen-agers use them:)
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