Different Cranks = different chain lengths?!

[Vetplant]

Quick history:

Rode 53-39 crank, no chain drops, ever.

 

Then swapped said crank for 50-34 without adjusting the chain length, then had plenty of dropped chains.

 

Swapped back to a different crank, but again 53-39, no chain drops since.

 

Was the 50-34 crank just a bit useless or should you change the chain length when you swap cranks?

 

I like the 50-34 for hillier terrain and the 53-39 for flat and fast stages with a sprint finish, so would like to be able to swap between the two.

 

Solution may be to have a chain with a masterlink for each crank?

[Barend de Arend]

You first need to look at your front derailleur.  It's should be a few mm above the big ring.  If the gap is too big the chain can drop.  Adjust your front derailleur down (which also means redo the cable)  Note: if the gap is too small it'll jam.

 

The second thing is to look at the type of front derailleur.  9 and 10 speed derailleurs couldn't reliably do 16 tooth gaps (50 - 34) but they could do 14 tooth gaps (53 - 39).  Sometimes it worked fine, sometimes it didn't.  See setup above.

 

You might have to remove a link (or three) when swapping a 53 chainring for a 50 chainring.  The crank doesn't matter; but the chainring size does matter.  Ignore this if your cassette is also bigger.  The easiest is look at the rear derailleur in big-big cross-chaining; and in small-small.

 

It might also be bad (worn) chainrings or bad chainring spacing if you're mixing and matching 9, 10, 11 or 12 speed rings and chains.  More speeds usually mean a narrower chain, and the spacing between small and big ring has changed.  Personally I've only encountered this problem on swapping 9 & 10 speed, but it's possible on 11 & 12 too.

 

 

edit: you can usually make it work, just depends on whether you're happy with 98% or 100%.

[travisza]

Quick history:

Rode 53-39 crank, no chain drops, ever.

 

Then swapped said crank for 50-34 without adjusting the chain length, then had plenty of dropped chains.

 

Swapped back to a different crank, but again 53-39, no chain drops since.

 

Was the 50-34 crank just a bit useless or should you change the chain length when you swap cranks?

 

I like the 50-34 for hillier terrain and the 53-39 for flat and fast stages with a sprint finish, so would like to be able to swap between the two.

 

Solution may be to have a chain with a masterlink for each crank?

 

By moving from a 53 to a 50 you are changing the length required by the chain so yes I would guess you may need to change the chain length based on the dropped chains you are experiencing.

 

It can't be loose on the small-small combination and can't overstretch the rear derailer on the large-large combination

[porqui]

I think you are getting your cranks and rings mixed.

 

Barend is correct

[JA-Q001]

Why not rather get a sub compact setup (52/36) and have 2 cassettes on hand to change on your wheel (say a 11/25 and a 11/28 or even 11/32 if you have a long cage RD.) This would mean that your front setups stays perfect (Your FD was probably too high with the 50/34 causing it to mis shift) When only change cassettes, you dont really have to make a lot of other setup changes.

[droo]

Chain length and FD height will change. Not by much, but enough to cause issues.

 

Mr Bump has the right idea.

[thisismyotherbike]

You first need to look at your front derailleur.  It's should be a few mm above the big ring.  If the gap is too big the chain can drop.  Adjust your front derailleur down (which also means redo the cable)  Note: if the gap is too small it'll jam.

 

The second thing is to look at the type of front derailleur.  9 and 10 speed derailleurs couldn't reliably do 16 tooth gaps (50 - 34) but they could do 14 tooth gaps (53 - 39).  Sometimes it worked fine, sometimes it didn't.  See setup above.

 

You might have to remove a link (or three) when swapping a 53 chainring for a 50 chainring.  The crank doesn't matter; but the chainring size does matter.  Ignore this if your cassette is also bigger.  The easiest is look at the rear derailleur in big-big cross-chaining; and in small-small.

 

It might also be bad (worn) chainrings or bad chainring spacing if you're mixing and matching 9, 10, 11 or 12 speed rings and chains.  More speeds usually mean a narrower chain, and the spacing between small and big ring has changed.  Personally I've only encountered this problem on swapping 9 & 10 speed, but it's possible on 11 & 12 too.

 

 

edit: you can usually make it work, just depends on whether you're happy with 98% or 100%.

 

I have to compliment you for this helpful and thorough post

[Long Wheel Base]

You first need to look at your front derailleur.  It's should be a few mm above the big ring.  If the gap is too big the chain can drop.  Adjust your front derailleur down (which also means redo the cable)  Note: if the gap is too small it'll jam.

 

The second thing is to look at the type of front derailleur.  9 and 10 speed derailleurs couldn't reliably do 16 tooth gaps (50 - 34) but they could do 14 tooth gaps (53 - 39).  Sometimes it worked fine, sometimes it didn't.  See setup above.

 

You might have to remove a link (or three) when swapping a 53 chainring for a 50 chainring.  The crank doesn't matter; but the chainring size does matter.  Ignore this if your cassette is also bigger.  The easiest is look at the rear derailleur in big-big cross-chaining; and in small-small.

 

It might also be bad (worn) chainrings or bad chainring spacing if you're mixing and matching 9, 10, 11 or 12 speed rings and chains.  More speeds usually mean a narrower chain, and the spacing between small and big ring has changed.  Personally I've only encountered this problem on swapping 9 & 10 speed, but it's possible on 11 & 12 too.

 

 

edit: you can usually make it work, just depends on whether you're happy with 98% or 100%.

You should charge for this good info.