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Old 10-11-11, 02:42 PM   #1
Jaytron
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From Triple chainring to double, what needs to be changed?

Other than obviously the chainrings themselves, what will I have to change in order for this to work?

The bike in question: http://www.bikepedia.com/quickbike/B...iple&Type=bike

(or at least using parts from that bike)

Do I have to get a new front derailleur/shifters/etc?
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Old 10-11-11, 03:29 PM   #2
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you've covered it with the Crank and FD, the current shifters will work fine. but you will need to remember that they have an extra click (shift) that can't be used.
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Old 10-11-11, 04:12 PM   #3
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you've covered it with the Crank and FD, the current shifters will work fine. but you will need to remember that they have an extra click (shift) that can't be used.
Thank you!

Brings me to my next question, I know finding a new big ring must be harder than just picking one that has the same number of teeth, etc. What other measurements do I need to be aware of?
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Old 10-11-11, 04:22 PM   #4
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Jaytron: When you set up the shifter/FD be sure to set it up so that the un-used shifter click is on the low end, that is, it slackens the shift wire further when you are on the small chainring. What you don't want is to be forgetful and attempt to pull more cable when the derailleur is already against the high limit stop. That could potentially jam the shifter ratchet.
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Old 10-11-11, 04:28 PM   #5
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Brings me to my next question, I know finding a new big ring must be harder than just picking one that has the same number of teeth, etc. What other measurements do I need to be aware of?
What are you trying to achive by going to a double from triple?

The standard double combinations are 53/39 or compact 50/34, if you want anything different, it will normally add to the cost as you will need to buy the regular cranks, and then additional chainings.

Also there is the cassette, there are many different combinations for this, dependant on what you go for, a longer chain may be needed.
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Old 10-11-11, 04:33 PM   #6
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What are you trying to achive by going to a double from triple?

The standard double combinations are 53/39 or compact 50/34, if you want anything different, it will normally add to the cost as you will need to buy the regular cranks, and then additional chainings.

Also there is the cassette, there are many different combinations for this, dependant on what you go for, a longer chain may be needed.
I was kind of just wondering. I'm moving the parts from one bike to a new frame, and I noticed one of the chainring teeth is chipped. I'm not sure if it'll be an issue or not so I'm trying to see if it would be easy to find a replacement chainring, or if i should just upgrade to a double at this point.
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Old 10-11-11, 04:37 PM   #7
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...I noticed one of the chainring teeth is chipped...
Are you sure it is chipped? Some modern chain rings (and cassette cogs too for that matter) are made with some teeth shorter than others, as well as ramps and pins, to aid in shifting. It is possible that what you are seeing is not a chip but actually the way the chainring was made.
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Old 10-11-11, 04:59 PM   #8
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Are you sure it is chipped? Some modern chain rings (and cassette cogs too for that matter) are made with some teeth shorter than others, as well as ramps and pins, to aid in shifting. It is possible that what you are seeing is not a chip but actually the way the chainring was made.
Could be, I'll check in when I actually get the bike running to see if I actually need to do something about it.
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Old 10-11-11, 05:10 PM   #9
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Triple to double .. the crank chainline needs to come in..both chainrings.

where the middle ring was , is now needing to be the space between the 2 chainrings.

measure and get an appropriately shorter BB.
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Old 10-11-11, 05:14 PM   #10
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Jaytron: With a different frame, even if you keep the same cassette and chainrings, you will need to check to be sure you have the proper length of chain. Too short could lead to disaster.
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Old 10-11-11, 05:43 PM   #11
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You can keep the same FD. I just went from triple to compact double and replaced only the crank and matching bottom bracket.
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Old 10-11-11, 06:28 PM   #12
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Triple to double .. the crank chainline needs to come in..both chainrings.

where the middle ring was , is now needing to be the space between the 2 chainrings.

measure and get an appropriately shorter BB.
Noted, thanks!

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Jaytron: With a different frame, even if you keep the same cassette and chainrings, you will need to check to be sure you have the proper length of chain. Too short could lead to disaster.
I have a brand new chain that I'm going to have to measure anyways

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You can keep the same FD. I just went from triple to compact double and replaced only the crank and matching bottom bracket.
Any problems at all? I know somebody that did the same, and he says it's basically just more trim.
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Old 10-11-11, 08:53 PM   #13
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You can keep the same FD. I just went from triple to compact double and replaced only the crank and matching bottom bracket.
Not necessarily.

Trying to get my Campagnolo Racing-T derailleur to work with an FSA 50-34 compact crankset I had to choose between not being able to shift to the big ring in all situations and often dropping the chain to the outside. A double front derailleur with different geometry and cage width worked perfectly.
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Old 10-11-11, 10:14 PM   #14
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Any problems at all? I know somebody that did the same, and he says it's basically just more trim.
Nope. Shimano doesn't have a compact specific double FD. Double FDs were originally designed for 53/39 and my triple had 52/39/30, so the FD had the same geometry as a standard double, except a taller/deeper inner plate.

I just lowered the FD to just barely clear the 50T and it works perfectly.
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Old 10-11-11, 10:15 PM   #15
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Not necessarily.

Trying to get my Campagnolo Racing-T derailleur to work with an FSA 50-34 compact crankset I had to choose between not being able to shift to the big ring in all situations and often dropping the chain to the outside. A double front derailleur with different geometry and cage width worked perfectly.
I have no experience with Campy, so maybe that's the case with it. For Shimano it works perfectly for me.
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Old 10-11-11, 10:21 PM   #16
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One more question, if I just wanted to replace my large chainring, are there any measurements I need to find out or keep in mind when I'm shopping for a new one?
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Old 10-11-11, 11:55 PM   #17
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Bolt circle... though if you reduce the difference between the 2 rings, like a 34/46, or 36/44

you won't get a triple FD to clear the inner without being extraordinarily high above the outer..
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Old 10-12-11, 08:26 AM   #18
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Bolt circle... though if you reduce the difference between the 2 rings, like a 34/46, or 36/44

you won't get a triple FD to clear the inner without being extraordinarily high above the outer..
If I replace just the chainring, I plan to keep it a triple. So if I get the bolt circle number, and match the number of teeth, I should be fine?
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