Bicycle Mechanics - Gear Talk Anyone?
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06-03-03, 09:01 PM
I've been sitting here trying to figure out if I want to put a double chain ring or triple chain ring on my Lemond Nevada City when I build it back up.
My K2 came with a triple configuration up front and 12/25 on the rear. I am finding that as I gain strength (and lose weight) I am using the granny ring less and less, but I like having it :)
What I've been thinking about trying is switching the current 12/25 cassette with a 14/25 cassette. I think I've put it in 53/12 once or twice and would really prefer to have gears I can use instead of sitting back there taking up space and not getting used.
So, has anyone out there with a 39/53 setup used a 14/25 cassette before? If so how did you like it compared to a 12/25?
If memory serves there's about 10 gear inches between a 30/25 and 39/25 - just how much of a difference is that when you're climbing a hill?
Also, does anyone know off the top of their heads how large of a cassette a short cage (tiagra) derailleur will handle?
Should I be considering other ratios on the chain rings instead of the industry standard 39/53?
Finally, just for grins, let's do a poll. Should I build my Nevada City with in double or triple?
06-03-03, 09:11 PM
Once you settle into a comfortable riding fitness level and are maintaining higher paces you will not want or need a triple on a road bike.
I have found that once you are at or close to 140 gear inches it is unlikely you will encounter a hill too much for you. Only in the mountains do I ever need much lower than this even when in moderate to poor shape.
06-03-03, 09:32 PM
You can go down to a 38 in the front and up to a 27 in the back. That will get you 38 inches.
Personally, I do not care for the industry default 53-39 combination; I use 50-42 / 13-26, 48-45-34 / 13-23, 45-42 / 13-26, and 52-44 / 14-28, all of which give me fast shifting and great sets of ratios with a 2-tooth step in back. I normally shift a cog at a time while accelerating, but I can always shift both derailleurs to find a ratio in between, when needed. (For use with 53-39, I would build a 14-15-16-17-18-19-20-22-24 corncob.)
Here is one way to analyze how may gear combinations you need:
1) Identify the lowest gear you need in practice, say, 40 inches.
2) Identify the highest gear you really need, say, 100 inches.
3) With an average of a 6 percent jump from ratio to ratio, you can cover this range nicely with 17 ratios, or as few as 15 if you can accept larger gaps at the top and/or bottom of the range.
4) A properly-designed 2x9 setup will yield up to 14 or 15 usable gears, thereby just meeting our criterion. A 3x9 would leave you with plenty of room for unused cross-combinations, redundant ratios, etc.
For commuting, club cycling, and unloaded touring, I find a gear range of low 40s to high 90s perfectly adequate. In practice, I generally reserve the gears below about 50 inches for that last long hill climb after a tough ride or that occasional 15-19 percent grade. Offroad or with a heavy load, I definitely want a triple, however! I'm not proud -- I geared my mountain bike 48-40-24 / 13-26.
06-04-03, 04:30 AM
A triple would be good for Six Gap but not much else in the Georgia area.
when I first got back into riding after an extended layoff
I appreciated the 53/39 combo, and that said I'd probably
keep it if I lived in a very hilly area (not much in the way
of hills in Dallas).
I also prefer the "old school" 53/42 with a 12-26 cluster
gets me almost anywhere I need to be.
Since you don't live in a mountainous area, I voted that you should opt for the double.
SteveE (currently riding 13-26/30-42-52)
06-04-03, 12:12 PM
I voted double, since you have a triple on the K2. If you are going to ride somewhere where there are serious hills, just take the K2.
Once you have a bike with a triple, how hard is it to change it to a double?
Just the cranks, or BB too? FD? RD?
06-04-03, 12:36 PM
The difference is pretty significant if you want to upgrade later. I vote triple, for that "it's there if you need it factor". Unless of course, you get into racing, but that may be cause for another bike anyways.
The differences include: New bottom brackett, with a longer spindle. Cranks (obviously), a new front derailleur, and a new front shifter. If you've got seperate shifter/levers (older bikes or bikes with downtube shifters) it's not a big deal, but if you've got the new integrated brake/shifter levers, this can be the most expensive item to upgrade.
Heck, you can get the triple, remove the granny gear and reset you stops on your front derailleur and have a double! (Although there is a slight sacrifice in chainline)
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