|   Estimating exact gear length for vert dropouts???? | JMD
Sep 12, 2002 9:12 PM | | After looking for a good custom SS cross frame this summer (other than Surley) I ran across a friend of mine who will sell me a Lemond Poprad frame for a sweet deal.This frame comes with vert dropouts for geared riding.I used the Fix Me Up program and determined that with 43 cm chainstays a 34x14 or 36x16 should work OK for cross with this frame and according to the program fit EXACTLY. I know there are people on this board who have run SS gear ratios exactly on vert dropouts -S othe question is will this work forever, or does chainstretch really occur? Will I have frequent chain droppings with this set-up? It seems like it would be pretty cool since I'd be ableto torque the hell out of the frame and not worry abot any axel slip or anything. Will this set up make getting the wheel in/out very hard as I plan to run it flip flip SS/fixed if I do get the frame. Thanks for the advice! |
| re: Estimating exact gear length for vert dropouts???? | crazy mike
Sep 12, 2002 9:46 PM | | Technically chains don't stretch but as the rollers wear, the chain fits looser on the chainring and cogs. Because you usually have a "new" chain for a week, and a worn chain for months (if not years) I would try to base your gear combination(s) on a used chain. Its more consistent.
If your first choice of gears doesn't appear to be an acceptable fit, try a similar ratio with an odd size ring. (or even if the first choice was an odd number) This will keep the chain tention snug and free from derailments.
As for wheel removal to flip the hub, most vertical dropouts face forward ever so slightly. I can almost guarantee this is the case with your frame so you should have no problem getting the wheel in and out.
crazymike |
| what's the url... | kam
Sep 12, 2002 10:29 PM | | for the fix me up page? i'm also contemplating on selling my ellsworth roadie and jamis dragon geary to build a singlespeed cx/road bike. i may go with a empella bonfire, soma double cross or maybe a used gunnar crosshairs or kelly knobby. those poprad frames are nice, good luck on your build.
cheers and thanks in advance. |
| <a href="http://www.peak.org/~fixin/fmu1.0.html">http://www.peak.org/~fixin/fmu1.0.html</a> NM | mtnbykr©
Sep 13, 2002 3:29 AM | | |
| Find a gear that fits, then work backwards | Ginz
Sep 13, 2002 5:06 AM | | It's very difficult to guess at a gear. The best way is to experiment and find a gear setup that fits, regardless of the ratio. Then, plug the chainring and cog into the fix me up calculator and it will return your chainstay length. Then, plug in more ring and cog sizes and you can scan down the list to see what ratios will work with that chainstay measurement. |
| re: Estimating exact gear length for vert dropouts???? | itsdoable
Sep 13, 2002 12:59 PM | | I've done this on a few frames, and in my opinion, you are better off with a eBB or horizontal wheel mounts. The amount of chain wear that allows a chain to fall of is pretty small. Getting a frame with a chain stay that is slightly short but within the 'fix-me-up' range works best, but you'll have to change the chain more frequently. Ofcouuse you'll have an automatic, if not painfull, chain wear indicator!
Hints:
- use a SS or BMX chain that has minimal lateral flex - derailure chains have designed in flex to facilitate shifting, or in the SS case - derailment.
- When the chain is too worn to stay on, you can use it on another bike as it usually still has some life left.
- many frames are designed in metric, quoted in inchs, or vice versa. The conversion rounding often makes the chain stay too long/short, plus variations in the frame jig will have effects from frame to frame. Measuring the frame to this accuracy is difficult, so the best way is to try a few combinations.
Good Luck. |
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