Crankset advice

[jorgemartin]

Hello, I'm building a new bike from salvaged bits and I need some help in choosing the right crankset. I have a 8 speed compatible rear derailleur (SRAM dual drive, short cage=75 mm), a 11-32t cassette, and 26 inch wheels. Because I'm quite tall I would look into 175mm crank arms and a three chainring crankset (but could also be two). What would be the right crankset setup to go for? And what about the front derailleur? Do these also come in different 'capacities'?
Thanks!

 

[TheDoctor]

Short cage and an 11-32 cassette? A triple is not on - the short cage mech won't wrap enough chain. Even a compact is going to be a bit much, I fear.
I'd use a single chainring if you have the bits - maybe a 42. That'll give you gears from 34" up to 99"
And yes, front mechs come in double and triple flavours.

 

[PpPete]

if your BB is Square Taper, this is good vfm.

 

[RecordAceFromNew]

Hello, I'm building a new bike from salvaged bits and I need some help in choosing the right crankset. I have a 8 speed compatible rear derailleur (SRAM dual drive, short cage=75 mm), a 11-32t cassette, and 26 inch wheels. Because I'm quite tall I would look into 175mm crank arms and a three chainring crankset (but could also be two). What would be the right crankset setup to go for? And what about the front derailleur? Do these also come in different 'capacities'?
Thanks!

I think you have a mid cage. If so their official capacity is 37T, with a 11-32 cassette leaving 16T for the front, so a typical triple up front might work, but chance is the chain might well be too slack on small front small back (not that it is a gear you need to go into, but still).

When choosing chainset you should ensure the chainset and bb match to deliver the correct chainline for the front mech, which should also be chosen to match the # of speed and profile of the chainset.

 

[jorgemartin]

The derailleur is short but the length of the cage is 75 mm, which makes it more a medium I guess (I have a short cage derailleur on another bike and is 55 mm)...

 

[RecordAceFromNew]

The derailleur is short but the length of the cage is 75 mm, which makes it more a medium I guess (I have a short cage derailleur on another bike and is 55 mm)...

In case there is any misunderstanding the cage length refers to the distance between the jockey wheels, which drives the mech's wrap range primarily. Separately the parallelogram dimension of the sram dual drive 24 rear mech should handle 11-32 fine, because that is their original sprocket spec.

 

[TheDoctor]

But I doubt it'll cope with wrapping the chain from a compact or triple - it's designed to work a wide ratio cassette that sits on a 3 speed hub gear. That's why I suggested a single chainring.

 

[jorgemartin]

I used to have a 3-speed Brompton (later stolen, alas) and always thought it was good enough a set up for my daily commute in London. I'm going to give the single chainring a chance. I'm getting a 38 teeth. I hope this is going to work...