Replacing triple inner ring - sanity check

roubaixtuesday

Veteran
Photo Winner
I'm going to replace the inner 26 currently with a 24.

Before I get started, a quick stupid question: I do need to take the crankset off for this, right? It's many years since I've done this and want to make sure I'm not missing anything obvious.

Oh, and also, 24 is the smallest I can go to? It's a 5 arm square taper crankset.

Thanks in advance
 

Sharky

Guru
Location
Kent
For the outer and middle rings, you don't have to take the cranks off, but as the inner is much smaller you won't be able to manipulate it off.
For the inner, what's the bcd?
 
Location
London
I think I'd take the cranks off anyway if they haven't been off in a while - helps to clean the cranks/chainrings/hidden bits of the frame.

and take the BB out if it's a catrtridge type and hasn't been out in a couple of years.
 
OP
R

roubaixtuesday

Veteran
Photo Winner
If looking for a smaller gear, have you explored cassette sizes?
Yeah, it's a Sora 9 speed. Currently have 11-32 rear, and mech is good for 34 officially. I'm going to try an 11-36, likely ok and will fit an extender if need be. It's a tandem, gears are manageable unladen - recently tried out in the Alps- but we're hoping to do some more touring, so lower the better! 24/36 definitely a significant change from current 26/32 lowest gear, effectively two gears lower.
 

YukonBoy

The Monch
Location
Inside my skull
According to Sheldon brown, the smallest for a 74 is a 24
I’d agree my xtr m970 crankset has an inner bcd of 64 and the inner chain ring is 22. This gives me a low gear of 22 x 34 on my recumbent.
 

si_c

Veteran
Location
Wirral
Yeah, it's a Sora 9 speed. Currently have 11-32 rear, and mech is good for 34 officially. I'm going to try an 11-36, likely ok and will fit an extender if need be. It's a tandem, gears are manageable unladen - recently tried out in the Alps- but we're hoping to do some more touring, so lower the better! 24/36 definitely a significant change from current 26/32 lowest gear, effectively two gears lower.
I've had no problems fitting a 36t to an RD-R3000-GS rear derailleur, as you might expect it needs the b-tension screw winding in a bit, but it works fine. I matched it with a 52-36 crankset so fitting it with a 24t smallest sprocket should be fine.
 
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