Campy SR EPS rear derailleur capacity

Discuss light weight issues concerning road bikes & parts.
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audiojan
Posts: 777
Joined: Fri Jan 27, 2006 1:38 pm
Location: New Hampshire

by audiojan

Anyone knows the capacity of a Campy Super Record EPS rear derailleur? I'm planning to use a 52/36 combined with either a 12-27 or 12-29, but I'm a bit worried about exceeding max capacity. For mechanical RD, I can always use a medium cage, but it doesn't seem to be such a thing for the EPS...
"Suddenly the thought struck me; my floor is someone elses ceiling" - Nils Ferlin

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bikerjulio
Posts: 1901
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

Assuming the geometry is the same (which it is) as mechanical, then the answer would be in the range 30-31T max total takeup, IF you want to be able to cross-chain both ways.

So, 52 - 36 = 16T. leaving 14T max for the cassette. So a 12-27 is stretching things at 15T. Chain length is critical in this whole discussion.

Alternatively, if you promise not to cross chain into the small-small combos, then you can go wider range. Just size the chain on the big-big for safety, and remember that the RD will run out of capacity as you approach the small-smallest sprocket. So, if using the 52-36 and 12-29, the chain, if correctly sized, will start to sag around the 36-14 point. So, still quite safe and useable.

Also if using a 29T sprocket on mechanical, it's worth checking and backing out the "H" screw for max clearance. Don't know how EPS RD handles this, but there's always the instructions. :) Regardless, it is compatible with a 12-29 cluster.

edit.

Just checked the tech specs. EPS and mechanical RD's have the same takeup capacity, since their sprocket spacing is the same at 55mm. The same as the previous generation also.

ps. loved that the EPS battery has a case of
Fireproof technopolymer
. Good to know in case your bike is trapped inside a burning building.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

audiojan
Posts: 777
Joined: Fri Jan 27, 2006 1:38 pm
Location: New Hampshire

by audiojan

Thanks for the great and detailed info! 12-27 with 52/36 would give her the range she needs in all terrain we ride in. Right now, her bikes are all 53/39 with 13-26 or 13-29 cassettes (swapping to fit the terrain).
"Suddenly the thought struck me; my floor is someone elses ceiling" - Nils Ferlin

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bikerjulio
Posts: 1901
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

Advise buying the KMC 11-spd chain link. Makes correct sizing of the chain so much easier. Works great. No finicky pins or fancy chain tool required.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

audiojan
Posts: 777
Joined: Fri Jan 27, 2006 1:38 pm
Location: New Hampshire

by audiojan

Already planned to use the KMC X11SL chain. Have very good success with the X10SL...
"Suddenly the thought struck me; my floor is someone elses ceiling" - Nils Ferlin

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