View Single Post
Old 02-20-12, 11:35 AM
  #2  
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,430 Times in 1,343 Posts
Rear derailleurs don't care about the crank set either way, so no automatic issues.

But there is the question of chain take up capacity, regardless if whether it's a double or triple. The RDs cage length determines the capacity which is listed in terms of the number of teeth. You need capacity equal or greater, than the sum of the differences between the largest and smallest sprocket front and back, ie. 12-26 & 28-38-48 = 14+20 = 34t capacity needed. The capacity requirement is the same regardless of whether you have a triple or double with the same inner and outer chainrings.

There is a bit of wiggle room on borderline cases so if you need 29t and the RD you want has only 27t you might get by with careful chain measurement, and possibly not using the small/small combinations (which most don't use anyway).
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline