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52 tooth chainring on a compact crank?

20K views 18 replies 15 participants last post by  GTDave 
#1 ·
Well, I love my Fulcrum compact cranks. Except when I want to descend fast and I'm spun out. SO, here's the question...can I put a 52 tooth chainring on my compacts for mountainous races? Anyone?
 
#3 ·
sjbryson said:
Well, I love my Fulcrum compact cranks. Except when I want to descend fast and I'm spun out. SO, here's the question...can I put a 52 tooth chainring on my compacts for mountainous races? Anyone?

Making a 52-34?

I don't know about you, but little old me-but in most situations where I spin a 50/12 out-odds are I'm also going to spin out a 52-12 just about as quickly, yes? Not worth the bother, presuming it would work, IMHO.
 
#4 ·
Sure, if you have a 36 for your smaller ring. I think a 14-tooth jump is the most a front derailleur can handle.

You could also swap out your cassette for one with an 11-tooth cog, as I'm guessing you have a 12-tooth cog. A 50-11 will give you a bigger gear than 52-12.
 
#5 ·
"I don't know about you, but little old me-but in most situations where I spin a 50/12 out-odds are I'm also going to spin out a 52-12 just about as quickly, yes? Not worth the bother, presuming it would work, IMHO."

Well, that's what I thought too--untill I got passed by several people, spun out, on a steep, into the wind descent.
 
#8 ·
SRAM makes a 11-28 for a wide range of gear combinations. I almost got one, but decided to stick with Shimano and a 12-27 for my compact cranked Madone when I changed the cassette to make a climbing "super century" a little easier. My LBS told me Shimano is coming out with a 11-28 later this year (at least according to the rumor mill). That'll be sweet for the flats and climbing :p

Bruce in Redding
 
#10 · (Edited)
I think a 14-tooth jump is the most a front derailleur can handle.
Shimano compact cranks are 50-34; a 16 tooth difference, and they shift very well with a standard front derailleur.

I suspect a jump from 52-34, though, is going to be way too much and lead to less than idea shifting in the front. Plus I've never seen that combination, so you won't have the potential advantage of some creative ramping and pinning on the outer chainring to make the upshift smoother.

Also, if you're running an 11-27, 52-34 set up, chain wrap length may be an issue if you're running a short cage rear derailleur. You don't mention what type of rear derailleur you're using, but the recommended chain wrap length for short cage Shimano derailleurs is a conservative 29. 31 works fine. 34 may not.
 
#15 ·
TA Nerius chainring

If you want a 52T ring to fit a Fulcrum compact crank, you need a TA Nerius, as Fulcrum uses the proprietary Campy 110 + 112mm BCD. TA makes inner rings of 34-42T, and outer rings of 48-53T in this standard. Most front derailleurs seem to have a capacity of 16T, so you would likely need to use a 52T big ring with a 36T small ring. Alternatively, you could try using a triple front derailleur.
 
#17 ·
Eyorerox said:
A 52/11 @ cadence of 100 is 38 mph 50/11 is 36.5 mph
A 52/11 @ cadence of 120 is 45.6 mph 50/11 43.8 mph
Sheldon Brown
50/11 is fine for me, just coast when I spin out
Yep. At those speeds, a good tight tuck can net more watts than opening up to pedal.
 
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