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Old 12-05-08, 02:00 PM   #1
kbpfister
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How do I size my stem?

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.
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Old 12-05-08, 10:10 PM   #2
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Have you the original stem?
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Old 12-05-08, 10:48 PM   #3
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Check out your LBS. Mine will sell adjustable stems, if the customer really, really wants one, but they would rather just use one for fitting purposes.
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Old 12-06-08, 11:08 AM   #4
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I take it this is an old-style "quill" stem, with little wedge on the bottom to hold it in place?

No problem if so, almost all of these are nominally 1". The dimensions of more concern are the length and the angle, which affect your position on the bike.
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Old 12-06-08, 11:28 AM   #5
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Originally Posted by Bikewer View Post
I take it this is an old-style "quill" stem, with little wedge on the bottom to hold it in place?

No problem if so, almost all of these are nominally 1".
ALMOST being the key word. This is an old Schwinn, so the quill diameter is .833" (21.15mm) instead of the much more common 22.2mm. It may not sound like much, but to "widdle" 1.05mm of material off a quill, as the OP plans, is a lot of trouble unless you have a lathe and know how to turn odd-shaped objects on it.
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Old 12-06-08, 05:32 PM   #6
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Yes... and he still hasn't answered my question, which is fundamental to my answer to his query.

Giant made a bike with smaller-than-standard quill... it's sitting outside slowly mouldering away because of the problems rebuilding it (the BB also is an odd set-up).
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Old 12-06-08, 06:58 PM   #7
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"whittle", not "widdle"...

But anyway, how I determined my reach was to put my hands on the bars wherever they made ME feel good, regardless of whether I could reach the brakes or not. Then I found a stem to bring the bars to my hands.

If I had to move them more than 2 cm, I would've done better with a different size of bike.
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Old 12-06-08, 08:02 PM   #8
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sorry I'm late

I do not have the original stem, however the bike did have some crappy Schwinn cruiser stem in it, so I do know that the dia. is 21.1 mm, I'm actively looking for a vintage stem to go on the bike, but haven't had any luck so I was thinking about buying a new one. I didn't ride the bike for very long before taking it apart, if I had I could have gotten a better idea of where I needed to be length wise. it's just going to be my around town bike but I thought I would try to get something that fit right. I haven't really been riding long enough to know exactly where I like my hands, just wanted to know if there was a sort of rule of thumb to calculate a suggested forward length based on my frame size and maybe my height or something. I have a stem that will fit that's on another bike, so I'll probably just pull that one off put it on this bike ride it around and see how it feels and just get a new one longer or shorter.

FYI I was planning on just using a belt sander to whittle(thanks for the SP correction) the stem down, others on the forum seemed to think it was no big deal, but I do know some metal guys that might be willing to turn it for me
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Old 12-06-08, 08:13 PM   #9
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FWIW, a close-but-bad fit doesn't start to hurt me until about 20-30 minutes into riding. It sucked when I got half an hour out and started hurting bad enough to turn around, then had to suffer for another half hour just to get home.

There are a few online fit calculators out there; Competitive Cyclist has one. Get a friend to help you measure everything (and I mean everything... so they should be a good friend.. ), measure several times, and see what numbers they give you.
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Old 12-07-08, 01:49 AM   #10
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I take it no other bikes you ride handy to measure? Also are you using flat or drop bars? Bike shop fitting setups are usually oriented around drop bars and a sporting type fit, at least in my area.

One old rule of thumb was with the hand outstretched place the elbow against the front of the seat nose. The tip of the longest finger should just touch the handlebar. You need the saddle in the desired horizontal position first. Of course if you are built like an orangutan this will not work well.

For me this is too short. I prefer about an inch more for drop bars and several inches more for flat bars. One difficulty is desired stem length can vary considerably depending on bar height and how forward a lean you want or are used to. Also as muscles become accustomed to riding the desired bar position can change.

Another one is that the arms should be held out straight at about 90 degrees to the body. While seated on the bike lean forward to the desired torso angle. Locate the bars so the hands can grasp them in that body position. Keep in mind that too upright can be as bad as too much body lean.

The technomic stem has a long quill so it can be adjusted over a fairly long height range if your fork tube is long enough.

Last edited by tatfiend; 12-07-08 at 01:50 AM. Reason: Gorrect spelling
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Old 12-07-08, 02:14 AM   #11
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Originally Posted by tatfiend View Post
I take it no other bikes you ride handy to measure? Also are you using flat or drop bars? Bike shop fitting setups are usually oriented around drop bars and a sporting type fit, at least in my area.

One old rule of thumb was with the hand outstretched place the elbow against the front of the seat nose. The tip of the longest finger should just touch the handlebar. You need the saddle in the desired horizontal position first. Of course if you are built like an orangutan this will not work well.

For me this is too short. I prefer about an inch more for drop bars and several inches more for flat bars. One difficulty is desired stem length can vary considerably depending on bar height and how forward a lean you want or are used to. Also as muscles become accustomed to riding the desired bar position can change.

Another one is that the arms should be held out straight at about 90 degrees to the body. While seated on the bike lean forward to the desired torso angle. Locate the bars so the hands can grasp them in that body position. Keep in mind that too upright can be as bad as too much body lean.

The technomic stem has a long quill so it can be adjusted over a fairly long height range if your fork tube is long enough.
This is what I was going to suggest, but with the index and middle fingers of the other hand placed at right angles to the fingers of the outstretched hand. That brings the distance into the range of dropbars.

The alternative is to measure with a tape, on a bike that already fits, from the nose of the seat to the centre of the stem's handlebar clamp. Then repeat the measurement from the nose of the Schwinn, note where the quill part of the stem would be, and deduct that figure from the total length -- that should give you a ballpark figure.

It is not easy to get an accurate estimate, unfortunately, and it is dependent on other factors such as seat position and your body dimensions.
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