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How tough is a triple to double swap?(10 posts)

How tough is a triple to double swap?t0adman
Jun 24, 2003 1:34 PM
I just got my new-to-me 2002 Lemond Zurich and was a little surprised to see it was a triple. I think I'll end up liking the granny gear on the hills around here but I was curious how tough it is to swap it for a double. Does it require more than just changing out the chain ring? What other considerations are there? Thanks.
See me not shouting "Don't do it!"?Silverback
Jun 24, 2003 2:06 PM
Not worth the trouble and expense, as far as I'm concerned, but I NEED that little granny...there are no disadvantages beyond a few ounces of weight. But that's not what you asked:
I've only done it the other way, double to triple. That took a new crank, new, slightly longer BB spindle and in one case a new derailleur. Easy job, if you're somewhat familiar with the tools and parts.
Turning it around, you'd want a new, slightly SHORTER spindle (probably could use the existing one, if you don't mind a large Q factor) and crank. Old front derailleur should work; just adjust the limit screws until the chain quits falling off. And for best shifting you could replace the rear derailleur with one that has less capacity, since it will have to take up less slack. I don't think I'd bother with that, though, unless I had a problem.
As I said, the whole deal makes no sense to me. But I'm a lousy climber, more embarrassed by not being able to get up a hill than by having to do it in a 24t chainring.
i'll start explan, but i think i'll need some help . . .bm
Jun 24, 2003 2:07 PM
from my little building experience i can tell you it's expensive and more labor than you expect.

first off, yes you have to change the chainring . . . but that means you change to a shorter bottom bracket and cranks. . . . that is why the sell cranksets . . . so you don't have to piece together cranks needed for a certain crankset.

then, you might have to change the front derailer . . . a triple front derailer has a larger tooth capacity . . . meaning, it has a wider plate area to compensate for the very large ring and smallest ring . . . i don't know if this will work for a double, but i'm thinking the performance may go down.

as for the rear derailer, you might want to get the double version (aka short cage) for the same reason . . . i believe a triple rear derailer is longer to accomodate the longer BB spindle width

i don't know for sure if you have to change the shifters . . . because there are, i believe, both triple and double versions for shifters too . . . i think you might be able to use a triple STI for the front, but i can't say for sure. . . if you change out those too, you'll have to retape the handlebars and recable

cranksets and shifters will be the most expensive parts . . . cranksets from $70 for 105 to $??.?? for dura ace. . . bottom brackets $30 to $50 . . . sti shifters $100-$200 . . . rear derailers $30-$60 . . . front derail $20-$40

so you see, it's at least a $200 job . . . and these are just estimates. my suggestion is that if you do decide to do this, go for parts on sale and throw in a coupon. (for instance, nashbar's got a shimano sale right now)

and when you feel comfortable with your own tools and bike knowedge, try to do it yourself . . . i don't know what it costs to do this at an LBS . . . but they do it a lot and my guess is $$pricey. . . . just have them check out the BB . . . the BB tightness has to be just right.

one more issue is the removable and installation of crank arms. . . sometimes it requires specific tools . . . other times you can just use an allen wrench . . . this is the one area i'm a little confused about.
Shifters.......Rusty Coggs
Jun 24, 2003 2:24 PM
Since it is 9 speed ultegra,front shifter is not an issue.It shifts a double or triple.... With older shimano shifers that were triple or double specific,the Triple version would also shift a double.
NOT toughwongsifu_mk
Jun 24, 2003 2:54 PM
Did the same thing on my previous machine. I went from triple to double (Ultegra) and only changed the BB and cranks(!). I adjusted the limiters on the front derailleur and shortened the chain. The long rear derailleur looked out of place in a double set up, but it worked just fine.

It's cheating, but it worked.
Related Question..VaughnA
Jun 24, 2003 4:59 PM
My wife has a small 47cm Trek 2000 WSD (105 components) with a triple. I don't know if it is the shorter wheelbase or what but it is very hard to tune the front derailleur for quiet operation. If she even slightly cross chains (not all the way) it rubs the cage. A friend who also rides a small frame said that he had the same problem and went back to a double with a 32 tooth MTB cassette. He said that is shifts much better than the triple. I have a slightly used cassette so I am considering getting her a crank & bottom bracket. So that is all I would need? Any opinions?
you would also need a rear derailleur -rockbender
Jun 25, 2003 12:32 AM
You would also need a mtb derailleur. The maximum cog capacity of Shimano road der's (to the best of my knowledge)is 27T.

My GF runs a double with an 11-34 XT cassette and loves it. Number crunchers here can give you the exact ratio's, but it actually gives her a slightly lower gear than my triple with a 25T big cog. Also, consider replacing the 53T ring with a 50T when it is time to replace the 'rings so that she can get some use out of that 11T cog.

The only disadvantage to this setup is having wider gaps between gears, though my GF doesn't mind this a bit.
i've done it..._rt_
Jun 25, 2003 7:45 AM
yes, it requires more than just changing out the ring.

for best performance you will need to switch out the BB, cranks/rings, front der & rear der.

initially, i tried just dropping off the granny gear but had huge problems with the chain being thrown to the inside & getting wrapped around the chainring bolt sleeves. even with the front der adjusted as well as possible, it still tended to overshift. i tried a chain catcher and that didn't work well either. so i ended up switching everythign out (good excuse to upgrade from 105 to Ultegra!)

as others have said the BB spindle length for a triple is longer than for a double. you'll likely need a BB with a 109.5mm spindle length.

the front der cage is smaller/narrower for the double. if properly adjusted the smaller cage will prevent overshifting.

the rear der cage is also shorter & will improve the precise-ness of shifting.

the difference between the triple & double cranks/rings goes without saying! ;-)

because i was working at a shop when i did my switch-out i have no idea what it would cost including labor.

rt
Where do you live?Spoke Wrench
Jun 25, 2003 7:48 AM
I've got a lightly used 2,000 Quantum Race that I'd like to swap the other way. If you live within striking range of St. Louis, I'll do a professional job for FREE.
Where do you live?t0adman
Jun 26, 2003 8:49 AM
Seattle, WA. Sorry.