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1 tooth,1 link,1/2 link=how much chainstay length? (6 posts)
|  1 tooth,1 link,1/2 link=how much chainstay length? | slide rule
May 25, 2003 8:19 PM | | I've been using the Fix Me Up calculator (love it, it got me here), but I haven't been able to glean the pattern...
Seems 1 link = 1/2 inch of chainstay (they say that on Fix Up).
But what about teeth? Does it depend on how many you've already got?
I keep thinking that +1 tooth on the front at the same time as -1 tooth in the back = same gear (you know, like gain ratio or gear inches, whatever, GEAR)... but that doesn't work the same way for chainstay length, obviously. How DOES it work??
The reason I'm trying to go into it, even though Fix Up seems to work well, is that I want to do another vertical dropout conversion, or, based on a gear combo that already works, predict how much filing of the dropouts it would take to use a different combo.
BTW, I recently arrogantly opined on this board that I don't know why more people don't just file their dropouts for verty converties... then tried to change the gear combo on mine (to another that looked on Fix Up like it should use the identical chainstay length to what I was already running, just a longer chain) and got slammed with massive chain ejects. Maybe one of those 1/2 links will help -- but my question above would answer how likely it would work, or whether it'd just put me in a different no-fit range.
I still like the simplicity of the filed verts, can't afford anything custom SS now, but my current success might be based on running 30:15 and being able to get away with a lot of chain slack just because of the steep angles between free chain and cog tangent (I hope you know what that means even if I don't).
Any thoughts (or flashcards)? |
| Search the archives.... | Brandon
May 25, 2003 9:11 PM | | I actually sat down and figured out a reasonable formula a while back so you could plug it in and start changing variables. |
| 1/8",1/2",1/4" (more) | Frank Tuesday
May 26, 2003 5:48 AM | | That is a close approximation. The formula is actually more complicated, as it depends on the difference in cog/ring size to determine the angle that the chain deviated from the center line of the cog/ring centerpoints.
So, if you change the total number of teeth by multiples of 4, or keep the total tooth count the same, it should work relatively well with the same chain length. With a half link, change in multiples of two.
frank |
| try this... | poison chicken
May 26, 2003 9:52 AM | | it is a bit more difficult that it looks. it is a function of 2 variables. that is chainstay length changes depend on both front and back teeth. in other words, if you have a 34x17 and add one tooth on the front, the chainstay length will change differently than if you have 36x18 and add one on the front, (back), etc.
get my gear calculator and use the third tab...i think it is "combination" and plug in whatever, say 34x17, then change, find possible chainstay lengths, then change to 35x17 and subtract the difference.
http://www.teambigtime.com/software/ssConvert.htm |
| try this... | poison chicken
May 26, 2003 10:59 AM | | let me clarify one thing...i am not saying that chainstay length is a variable in the general case (it is fixed length)...but for what you are looking to do...in theory, we can make it a variable. |
| try this... | slide rule
May 27, 2003 9:56 AM | | that's pretty damn cool. thanks. |
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