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triple to a double?(9 posts)

triple to a double?badgerbike
Dec 20, 2001 7:01 AM
What exactly needs to be done to convert a triple chainring to a double? Do I have to replace the derailleur? Thanks.
simplest methodgoldengopher
Dec 20, 2001 7:18 AM
Remove the inner chainring and adjust front derailleur- tada! You now have a double.

The 'real' way requires at least new front and rear derailleurs, crank and maybe bottom bracket.

The real questions is- why?
re: triple to a double?Drummie
Dec 20, 2001 7:30 AM
I looked into this a while back. I have a Specialized triple crank on an otherwise full Ultegra bike that I want to convert to an Ultegra double. This is what I was told I needed to do.

New Double crank (pretty obvious)
New bottom bracket (109.5mm instead of 118.5mm)
Could keep the rear deraillieur, but I was told that the double (shorter cage would shift better). Same for the front.
Possibly shorten the chain? Don't know about this one, but seems like you could go shorter if you go with the shorter cage.
I was told that the Ultegra shifter (STI) will work fine for the double so no need to replace that.

For my upgrade I was looking at $95 (Ultegra Double crank) + $25 (Ultegra 108.5 BB) + $29 (Ultegra Double Front derailleur) + $39 (Ultegra Double Rear Derailleur). So at the tune of almost $190, I took the inner ring off of my cranck (which on the Specialized crank looks just like a double when it's off) and adjusted the front derailleur out. I'm happy with the shifting on the long cage (rear) so I'm OK for now. I'll slowly pick up the parts on closeouts (supergo has some good deals now) until I have them all. Good luck, let us know how yours works out.

Drummie
so you did it for the look???SAD
Dec 20, 2001 7:47 AM
You didn't say you changed cassette or chainrings, so it seems that you did it just for the sake of having a double vs. triple. Perhaps the peer pressure of having a triple and its apparent fredness vs. a macho double..... That's just SAD.
so you did it for the look???Drummie
Dec 21, 2001 7:16 AM
SAD...

I didn't do it for the looks. I live in Florida and there is absolutely no reason for me to have a triple here (and I've done some of the biggest "hills" in the state - Clermont). The cogset is the same as I would be running if I had a double, no need to change that. I thought about switching to a 39 from the 42, but in this flat area it works fine. My biggest challenge on a weekend ride is a causeway. So your assumption that this was a fred/macho move is the actual SAD thing. Ease up!
you should look at the ring and gearing combinationscioccman
Dec 20, 2001 8:03 AM
before you just rid yourself of the small ring. You'll likely struggle on that 2nd ring when climbing compared to others with different gearing setups. Put plainly, to achieve the equivalent of the lowest gear possible in a dual setup, you NEED that small ring. I believe the 2nd ring of the triple is a 42 or 43, maybe 44 ??? or so while most are running 39s in the double setup.

You will likely take away any sort of climbing setup. A 39x25 will be a world of difference when compared to a 43x25.
you should look at the ring and gearing combinationsTriBuddha
Dec 20, 2001 9:10 AM
I also looked into this not so long ago, I run a 54/42/30 and not really comfortable with the 42, but after looking into the cost of changing my 105 components, it did not make any sense at all and will change to a 39 middle instead. This will allow me to run a tighter block instead so that I have use of a 16/17/19 or something like it.
I'd do the sameTig
Dec 20, 2001 10:38 AM
Running a middle 39 makes sense to me. If I ever buy a triple I'll do the same thing. Having a 12-21 cog set allows you to use those sweet spot gears with the 39 in the flats and easy hills, yet still allows for some super low combinations thanks to the small chain ring.
39T?Chen2
Dec 20, 2001 10:56 AM
The only 39 tooth ring designed to run on a triple is the middle ring on the new Dura-Ace triple. If you stick any other 39 in the middle of a triple it's not going to shift right when shifting from the small ring to the middle. The middle rings on triples are specifically designed to lift the chain up off the granny ring. Campagnolo makes a 40 for the middle of their Racing T and even it won't run on their new Record triple. All of the Shimano triples except the new Dura-Ace come with a 42T middle ring. I'm interested to see if the 39 from the Dura-Ace triple will run on an Ultegra triple, I expect it will.
-Al