|Campy conversion to FSA compact crankset?||hdnoise|
Dec 17, 2003 1:57 PM
|I am running record 39/52 with 12/25 and want to go much lower but without a triple. I see the choices are 13/29 cassette with a new mid cage rear derailleur or FSA carbon compact crankset @ 50/34 (with maybe (?) a new front d with a long cage) I am curious as to what others have experienced with either set up, pros and cons. Thanks for your input.|
Dec 17, 2003 3:52 PM
|You may not have to change the either derailleur to use a 50/34, but you may not be able to use the 34 with either of the top two cogs. Not a big deal. Adjusting the chain length must be done properly to avoid problems in either of the extreme, useable, combinations.
It is possible to use a 13-29 cassette with a short cage derailleur, but it's not guaranteed to work with every frame. On some frames the RD won't clear the 29T cog. Once again, the capacity of the RD is exceeded, and it requires the same caution to avoid the little ring and top two cogs where the chain may hang loose.
You will get about the same low gear with a 50/34 or a 39/29. With the 50 a bit more top gear is retained, since the 50/12 is about 4% higher than a 52/13.
All a 50/34 does is take 6% from the top gear ratio and increase the low by 13%, for a net increase in range of 7%, which is slightly less than a typical 1-cog change. In other words, you can get the range of 11 cogs with 10, but NOT without some expense.
The problem I see is the large amount of cog shifting required after every chainring shift. Most often, it requires a 4-cog shift to resume a uniform gearing progression, compared with a 2-cog shift for a 53/39. Ergo and STI levers will only shift up to 3 larger cogs, requiring two strokes of the shift lever after a shift to the big ring. Ergo levers can shift down 4-cogs with the thumb button, so the shift from the big ring to the little isn't quite as bad with ergo levers.
A 50/34 is probably a descent solution for folks who ride hills, but not mountains. For mountains, even lower gearing is nice and a 53/39/30 triple is a better choice. With a campy drivetrain the shifting can be as good as a double. It's all in the setup. The trick I found is to place the FD no more than 1mm above the big ring.
|least expensive approach...||hdnoise|
Dec 17, 2003 5:51 PM
|... so the lower cost and shift friendly solution is the new 13/29, keep the dr's and watch the crossover... until I discover I need a triple... Thanks again...|
|Ergo should be...||divve|
Dec 18, 2003 12:20 AM
|...able to shift down the full cassette in a single stroke using the thumb paddle.|
Dec 18, 2003 6:06 AM
|Hopefully all campy users know that the thumb button will execute up to 9 shifts with a single stroke of the button. I was merely pointing out that the thumb button can easily do the required 4-cog shift, not suggesting that is was limited to 4-cogs.|
|Done it recently||terzo rene|
Dec 18, 2003 12:28 PM
|Works fine with standard Record F der, just need to shorten the chain a bit. If you have a braze on f. der it could be an issue if you can't get the der. low enough to stay close to the 50 ring. I found the cranks for $300 shipped at wisecyclebuys.com so it didn't hurt quite as much.
I use either an 11-23 (which is not much lower than your currnt) or a mixed cassette with 11,12 low gears replacing the 12 & 13 on a 12-25 cassette.
|Done it recently||tommyturbo|
Jan 7, 2004 11:54 AM
|I run 53/39 with 13/29 Record. I am about to go to FSA 50/34 with 12/25 for my everyday setup. 34/25 is almost the equivalent of 39/29 but 50/12 is a little higher than 53/13. Even better, the low gear ratios will be closer than with my existing setup. When I go mountain touring, I will use 50/34 with 13/29 giving me the same low gear as a triple with 30/26. 50/13 is 106 gear inches which should let me pedal to 30 mph or so. Has anyone considered this setup? Do you see any drawbacks other than having to switch cassettes? Lastly, I was not aware you could customize campy 10 cassettes. Can you do 12/26, swaping the 25 for a 26?
Thanks for the help!