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Old 04-19-11, 07:43 PM   #1
ponyyyyyyy
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stem engineering

I've got an interesting question and sorry if it sounds immature or just plain dumb. What makes a stem so complicated? I mean certain components I can understand the variety in price and performance, but I just don't understand the affected performance improvements of a $200 stem over a $20 stem. I can go as far as understand possibly weight shavings, especially those with a longer reach who can benefit a weight shaving at 140mm. Now I know material will have price variances, but in the end, what mechanics does a stem provide that would persuade your wallet. Is it stiffness? Looks? Weight? Name? Build quality? Don't mean to be ig'nant just want to know as I'm looking to purchase a new stem.

edit: also what's the difference between a 'track' stem vs. a 'road' stem? is there?

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Old 04-19-11, 08:39 PM   #2
sideshow_bob
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Historically a lot of track bikes had very road like geometry, with longish headtubes. So to get riders down low enough, 'track' stems had more drop on them (like -10deg) or more.

Today a lot of track bikes are built with really short headtubes (so people can pursuit on them as well), and accordingly you don't need the stem to make the drop work. In fact a lot of bikes, like pretty much every BT will use a stem flipped up.

Past that stems are stems and just like any other bike component you pay for weight, stiffness, material and the name on it. Is that 100g ultraliteweight carbon stem any better than a 200g Thomson that will last forever? Depends how much that 100g means to you. Same with the brand really.

But in terms of your question is there any magical engineering in there? Not really.
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Old 04-19-11, 09:17 PM   #3
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As an engineer looking at a stem, there is very little that needs to be done to analyze it in a large company. What loads and criteria it needs to meet are set, the rest is just optimization and physical testing to match the analysis. The short version... Stems cost $200 because people pay $200.
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Old 04-19-11, 10:14 PM   #4
ponyyyyyyy
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ah, that is quite interesting. yeah right now, 100g is not worth the $200, especially when I can save it elsewhere for cheaper. Thanks.

actually another interesting question, is there a difference between 2-bolt face plate vs 4? other than the obvious? should I exclusively trust a 4-bolt face?
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Old 04-20-11, 09:50 AM   #5
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Any time one metal thing clamps to another you need to make sure the clamp is smooth and round. There are two parts that do that on a stem, and in pretty high stress areas. Also one half of a stem pulls on the other in a bad way. So with a good stem you will get a better clamping interface, and better tolerence of the forces(stiffness, sort of).
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Old 04-20-11, 09:54 AM   #6
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Quote:
Originally Posted by ponyyyyyyy View Post
ah, that is quite interesting. yeah right now, 100g is not worth the $200, especially when I can save it elsewhere for cheaper. Thanks.

actually another interesting question, is there a difference between 2-bolt face plate vs 4? other than the obvious? should I exclusively trust a 4-bolt face?
That is not to say that a $20 stem is just as good.

For the number of bolts, I would prefer a 4 bolt as there is a better chance of the pressure on the bar-stem interface being even, and as a result the reaction forces also even. I have no numbers and no calculations, or evidence for that matter, but my gut feel is that when we see broken CF handlebars, some of it may have to do with an uneven clamping force.
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