triple to double

[zaku]

3 questions...

1) can we just directly change a crank triple to a double without any other modification? does a short cage is absolutely needed? and shifter or front derailleur mod?

2) if the crank is said for 10 speed, what's the difference if we use it for 9 speed??

3) does the bottom bracket needs to be changed altogether with the crank?

 

[Retro Grouch]

3 questions...

1) can we just directly change a crank triple to a double without any other modification? does a short cage is absolutely needed? and shifter or front derailleur mod?

2) if the crank is said for 10 speed, what's the difference if we use it for 9 speed??

3) does the bottom bracket needs to be changed altogether with the crank?

It's actually possible to replae a triple crankset with a double. If you do nothing else you won't have accomplished anything except to cause your chain to drop off of the inside frequently.

You can adjust your front derailleur to stop the chain dropping, but your shifting won't be any better than it was previously and you'll get chain rubbing on the front derailleur in the crossover gear combinations.

To stop the chain rubbing you'll need to get a shorter bottom bracket to sweeten the chainline.

Your existing derailleurs, both front and rear, will work with a double crankset.

What are you trying to accomplish? Other than style points, there's nothing to gain by switching from a triple to a double. To get the style points, you'll also have to swap both derailleurs because anybody who cares will notice.

 

[nerdag]

1) can we just directly change a crank triple to a double without any other modification? does a short cage is absolutely needed? and shifter or front derailleur mod?

Depends on whether you are buying a new crank, or just taking off the inner ring, but an RD +/- FD change, are not essential.

2) if the crank is said for 10 speed, what's the difference if we use it for 9 speed??

None. The 10s rings *may* be marginally thinner, but not so much so that it will not work with a 9s setup.

If you have shifting problems using 10sp rings on a 9sp chain, stick some 0.6mm chainring spacers between the inner ring and crank spider, but you should be okay.

3) does the bottom bracket needs to be changed altogether with the crank?

Depends on what you're using (external vs. octalink/ISIS/square). If running an external BB, then no chance is necessary.

If you have a cartridge BB, then if you want a budget conversion, its not essential. If you want the narrower q-factor, then you'll need to switch to a shorter spindle BB.

HTH,

n

 

[capwater]

Please search the forum, this is a weekly question. Thanks.

 

[hd reynolds]

3 questions...

1) can we just directly change a crank triple to a double without any other modification? does a short cage is absolutely needed? and shifter or front derailleur mod?

2) if the crank is said for 10 speed, what's the difference if we use it for 9 speed??

3) does the bottom bracket needs to be changed altogether with the crank?

1) Since you're changing the crank better get the BB that comes with it. The 3ple RD need not be changed and FD will still work but you need to set it carefully lest you rick dropping the chain off inside.

2) Performance-wise non.

3) Possibly as per my answer in no. 1, specially if you're getting too much clearance.

 

[chainstay]

To stop the chain rubbing you'll need to get a shorter bottom bracket to sweeten the chainline. Your existing derailleurs, both front and rear, will work with a double crankset.

How about a triple specific left brifter, DA for example? Will it work with a double crankset?

 

[nerdag]

How about a triple specific left brifter, DA for example? Will it work with a double crankset?

Yes.

n

 

[capwater]

One question: have you used the search function of this forum? this is a weekly recurring questions. Loads of great info already discussed.