Bicycle Mechanics - Can this be done: Changing from a compact 3-disc crankset to a 2-disc crankset?
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After having broken in my new bike with nearly 1000 commuting miles on it, I've come to the conclusion that the stock 3-disc crankset (22/32/42) gearing is too short for my needs, and that the best setup would be a 2-disc set with 32/50 gearing or something close to that.
Can I somehow install a 2-disc cankset AND keep all the existing hardware such as the 3x8 Shimano shifters (see pic), stock front(Alfine)/rear(Deorde) derailleurs (again see pics) and Shimano UN26 (68x113) square taper bottom bracket and rear 11/32 cassette?
Also if the above is somehow possible, which crankset would you recommend?
-OR- would it be possible to change the chainrings on the existing FSA/RPM AL-8 crankset to a range more compatible to what I need? (mind you, that I have checked around for a 24/34/48 crankset and found some cheap units which my LBS didn't recommend.)
Maybe you could find an adapter that lets you mount a 130mm PCD road ring? That'd be the simplest way by far.
I'd be loathe to change the cranks, to the point that if I couldn't find such an adapter, I'd look at having one made. Have to be cheaper than a crankset.
Only downside would be the lift pins/shift gates would be intended for a bigger ring than 32t, but I bet it'd still shift better than a plain ring.
04-01-12, 01:41 AM
Dump the BB too, for a shorter one = to losing the 1 chainring.
Oh yeah, your MTB FD almost certainly won't work with a 50t; might wanna check out this thread (http://www.bikeforums.net/showthread.php/808214-XT-shifters-with-a-Dura-Ace-FD).
To answer your question, changing the cranks will require a BB and prolly FD. RD will be fine, although the cage will be longer than required; a road derailleur might be slightly better but is hardly necessary.
This thread is starting to sound expensive... what if I could find a Deore/XT 24-38-48 Crankset (relatively cheap on the net) and pair it with a Deore XT 8-speed IG 11-28 cassette, would that setup work with the currently installed derailleurs and shifters?
Found this: Alivio FC-M-411 48/38/28 (http://www.roseversand.com/article/shimano-alivio-crankset-fc-m-411/aid:287945) and it says that I need a B/B with axle length 122mm instead of the 113mm that's already installed.
...also this: CS-HG 70 8SP 11-28 (http://www.roseversand.com/article/shimano-cs-hg-70-8-speed-cassette-11-28/aid:45403)
04-01-12, 02:59 AM
Get a 12-21 cassette and learn to spin!
04-01-12, 07:00 AM
When I originally built my recumbent I put a 22/32/42 crankset on it because that's what I had in my spares box. Shortly thereafter I bought a 48 tooth big ring and installed it giving me a 22/32/48 crankset. All that I had to do was to raise the front derailleur a little and lenghten the chain a little. Shifting was fine, but I use friction barcons for the front chainrings.
Riding-wise it was great. The 48 tooth chainring gave me more top end speed than I normally use. I did almost all of my riding in the big ring and only shifted down into the middle ring steep hills. I thought of it as a 48/32 compact crankset with a granny bail out gear (which I never used).
Relative inexpensive too.
Bill, you want to spin me into an early grave! lol (don't forget, I'm a big Clyde!)
So what you're saying Retro is basically changing the front Crankset (can't find just the chain ring, already looked!). I remember bringing this up again in the past, and will probably proceed in getting a 28/38/48 like the one in the link in my previous post.
04-01-12, 10:07 AM
That 16 tooth jump from a 34 to a 50 on a compact crank is a slow shift. I know it's made me appreciate being able to spin at high cadences in the low chainring just to avoid it if I won't be in it for awhile. Going clipless has cut back on the amount of front shifting I need to do.
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