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Old 04-26-20, 01:16 PM
Join Date: Sep 2019
Location: SF Bay Area
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Bikes: 79 Holdsworth Special, 93 C-dale MT3000 Tandem, 96 C-dale F700CAD3, Two Cervelo R3's 2011 & 2018, JustGo Runt, Ridley Oval, Kickr Bike 8-)

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RD-6700 mystery solved.

OK between the Shimano Doc provided by Bill and some more research I've worked out what is going on here.

I going to state the obvious to most, but I've never seen this explained so here I go...

Shimano is rating their REAR Derailleurs in three ways
1. Max Front Difference
Example - my 50/34 crank setup has a difference if 16
2. Max Low Sprocket
This is the teeth on the largest Cassette cog. My current is 28T (I want 30T)
3. Total Capacity
this the Front difference + the rear difference. In my current setup 50-34 + 28-11 = 33 (I want 50-34 + 30-12 = 34)
Limit is 34 for the RD-6700-A SS

Here is clip from Bill's Doc.

As you can see the RD-6700-A will accept a 30T on the rear cassette and the Total Capacity (34) limit fits me need.
However what this does not tell you is that early versions of the RD-6700 were a non-"A" variant.
This non-"A" variant has a rear cog size limit of 28T and I suspect a capacity limit of 33. The non-"A" does not fit my needs.
To make matters worst, the RD-6700-A and RD-6700 are both marked on the rear as "RD-6700". There is NO "A" marking.
The way to tell them apart is the front of the cage is stamped 30T on the "A" version. The stamping is around the top pulley, you have to have the cage spring relaxed in order to see the marking.

I panic purchased a RD-6700 GS (long cage version) expecting it to offer a larger rear cog limit. Wrong - It offers a larger Max Front Limit. Rear cassette size is still limited at 30T.

I've since panicked another ebay 6700 and this time got a RD-6700 SS. Still not the RD-6700-A SS I was looking for.

I'm going to open up a business flipping RD-6700's for a living.

If you see a RD-6700-A SS NIB I'm in the market for one.
Until then, well I've got spares of everything else but !

I hope that seeing this spelt out with examples helps others untangle the mystery of Shimano spec's

EDIT: If you're wondering what version 6700 you have this post should clear that up.
All the best


PS - yes I know spec=rules and rules are meant to be broken.
I'm just attempting to remain within the rules in order not to stress the derailleur and to avoid the potential for catastrophic failure.
At 56 I don't heal so quick in the event of anything deemed catastrophic on a bike. 8-)

Last edited by Barry2; 05-06-20 at 12:25 PM. Reason: Added Link to Picture Post
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