Panic buy RD-6700-A GS for 12-30 ?
 

Current Setup -I currently have 50/34 R8000 cranks, 11-28 Ultegra Cassette and the original RD-6700 SS rear derailleur (non "A" version).

Problem -Hills have been an issue, I live on a rather steep one, ~480W required to climb it.

Wanted - I'd like to try 12-30 I know the RD-6700-A SS has the larger capacity for 12-30 but I can't find a new/minty one.
There are countless posts telling of how you can "stretch the Shimano Spec", and almost as many saying "Don't do that".

Panic -A NIB RD-6700-A GS just came available on Ebay and in a panic, I purchased it.

Question -Will this do what I want?
Would I have been better off waiting to find the SS I was looking for?

Thanks

Barry

The RD-6700 is a short cage model (SS), the RD-6703 is the longer cage style (GS) designed for triples. The "A" you are referring to is only for interchangeability of specific parts; its not really a part number. As far as I know, Shimano spec for both these 2 RDs is 28T cog max. The total capacity is what varies; 33T for the 6700 (designed for 2 x 10) and 39T for the 6703 (designed for 3x10). Of course, you can probably get away with using a 30T cog with the RD-6700 but you may have to turn the B screw all the way in.

Now onto the RD-6800. This is for 11 speed, where your old RD-6700 was 10 speed. This wont matter one bit. For the 6800 series, Shimano elected to add the SS and GS to the part number, which essentially mirrored the old 6700 and 6703 designations. Long story short, both versions of the 6800 are rated for 28T max cog. But again you can probably get them to work with a 30 T cog by adjusting the B Screw all the way in. The SS is rated fro 33T total capacity, whereas the GS is rated for 37T total capacity.

In closing, what literature are you referring to that specified your current RD-6700 is rated for a 30T max cog. Glad I don;t have that hill to climb.

1) Does your frame have horizontal dropouts? If so, you can probably pull the wheel back farther to give you a little more room in the 34/30 combination. If it’s still too close, take two links out of the chain and stay out of big/big. Vertical dropouts? Maybe, maybe not, but I’d still try.
2) Of course. And a new one at a great price will show up...any moment now. Such is the price of bicycling.

Here's a chart with Shimano's recommended cog sizes/chain wrap....

RD-6700 is the original and available in both SS (short) and GS (long)
Quickly replaced with the
RD-6700-A also in SS and GS

Both versions read RD-6700 on the rear ... but the "A" version has 30T stamped on the Cage of the SS version.

If confused as to how this relates to rear Cog size, and the other apparent calculation that take into consideration Crank teeth.

Barry

Your original RD should be able to handle the new cassette in terms of cleaning the largest cog. Your total capacity only increased by 1t, so there's a chance it'll be fine. If you really wanted to be safe you could have gone with a 9sp Shimano mountain RD.

Poor idea IMO, you are likely to forget and shift into that combo, likely causing damage if the chain is too short.

I have 4 bikes, all running 34/50 cranks, 11/32 cassettes and all using Ultegra 6700 rear derailleurs.

Since you’re going to use a 30t cassette regardless of the rear derailleur, I’d tell you to try the new cassette with your existing derailleur. You’ll have to adjust the B-screw so the upper pulley doesn’t clash with the large cog when in the Little/big combo.

Your new derailleur will work better with slightly larger cogs than your old one, so yeah, sure, it makes sense. The GS model will shift slightly less well than the SS but you're likely to not notice much difference. 2t isn't a giant deal, although sometimes all you need is a little more. If you want a bunch more range for relatively cheap a common solution is to run a 9 speed MTB derailleur (I'd recommend Deore or Deore XT level) with an 11-34 or even 11-36 cassette. For a lot of riders some kind of subcompact makes a lot of sense in very hilly terrain, also, if you really need lower gearing and don't care much about your speed in a dead sprint in a paceline.

Not my ideal either, but the OP was asking how it could be made to work. Caveat Emptor.
If it were me and the 6700 didn’t do the job, I’d switch to a Deore RD. Longer body geometry = easier to work with larger rear cogs.

+100. Don't even consider making the chain too short to allow big-big. If you have to compromise, make the chain a bit too long to use small-small which is no sacrifice and a lot safer.

I have a RD-6700-GS on one bike and it is stamped "30T" on the outer cage plate so it will take a 30T cog with no problem. I also have a NIB 105 RD-5701-GS in my parts box that says a 30T maximum cog with a triple crank and 32T max with a double.

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.
https://cimg7.ibsrv.net/gimg/bikefor...c6b885e271.jpg

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

Barry


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-)

Barry2, as I posted earlier; you have the 6700ss rear der already and you're going to use a 30T cassette. Why don't you try that combo as an easy experiment. Ride carefully and see if it will work to your satisfaction. If it does, it's a win for you. If not, change the rear derailleur.

I'm 78 and certainly don't want to be hurt on my bike. That said, I've been riding my bikes with a 32T cassette on my bikes with NO issues for over 5 years. Some of my bikes are off the rack, some are custom. They are made of steel or carbon or titanium. All are pretty modern, the oldest being a 2010 Look 585. All have a compact 34/50 crank. My point being that in multiple personal experiences, what I have works extremely well.

As another here has posted a Shimano 9-speed MTB derailleur is the best solution and will work with up to a 36T cassette with your existing components. This is a very common thing to do and used by many who tour and/or have many hills to climb.

Dave, seems weird, I understand the index is in the brifter, so a 9sp MTB rear derailleur could be convinced to jump 10sp. But only if the cassette were to be a 10sp.
I’ve seen Ultegra CS-6700 max at 12-30.
So, specifically what parts would you suggest for cassette and derailleur if I were to need beyond the 30T I’m planning for?

Thanks

Barry

The pull ratio of the Shimano 9-speed MTB rear derailleurs are the same as your 10-speed shifters so the der does exactly what the shifter tells it to do. You cannot use 10-speed MTB rear derailleurs with 10-speed road shifters, they’re not all compatible.

My wife’s bike, with 10-speed Ultegra components, uses a Shimano RD-M592 rear derailleur and an 11-36 cassette. It’s been operating for years now.

The RD M592 derailleurs cost about $50~$60.

I am not going to quote your whole past. Just thanking you for the update/research. I am guilty of giving you bad advise in the very first response. I was not aware that Shimano had made what essentially was 2 versions of the RD-6700, the difference being the "A" indicating the 30T max cog versus what I saw in documentation (without the A) as max 28T cog. It seems I am hearing more and more about component manufacturers making running changes to components and not really telling anyone. Sometimes it doesn't matter, and sometimes it does.


I don't have a spare of the derailleur you are looking for, but can vouch that if you want to use a larger max cog (e.g., 32T) then a 9 speed MTB derailleur is one way to go. They wont shift quite as crisp as the Ultegra, but work just fine with 10 speed STI shifters. See a few old Shimano 9 speed Deore, LX, and XT MTB RDs on E-bay in new condition, so may be one path. Good luck.

I think you are over thinking it. The GS will go up to 30 no problem

james
www.buckyrides.com

I have found the XT-750 to be quite good, and quick, with a wide range cassette. Can’t say how it compares with your Ultegra.

Of course, the grail rear derailleur for me has been an XTR 900/910 as they seem as quick as Dura Ace. Then again, an exceptionally clean one will cost a bundle.

John

The difference in gearing between a 34/28nand a 34/30 is absolutly negligible. you will never feel the difference. 30 inch gear v 32 inch gear. For comparison, the difference between a 53 18 and a 53 17 is 5 gear inches and I can barely feel the difference.

If the OP is barely making it up a hill with a 28, 2 more teeth will seem immense.

On paper it's minute, but in my experience suffering trying to drag my fat butt up a hill, the jump from 28 to 30 was absolutely significant.

"All I want for Christmas is my 2 front teeth"
 

UPDATE
I've every kind of RD-6700 that exists currently being shipped to me. So, no limitations there! :)

I've decided to use the RD-6700 GS (long Cage) and the Tiagra CS-HG500-10 11-32 Cassette.
This combination is well within the "Capacity" spec (40 is spec) and two teeth over the "Max Cog" spec (30 is spec).
By all accounts the RD-6700-A GS long cage will be fine with this. Plus I'm comfortable pushing the spec a little, now knowing exactly what/where I'm pushing it.

New Subject - what If I want even more T's.
I've also found a $20 device made by Wolf Tooth called a Roadlink.
The Roadlink does not increase the Capacity of a derailleur but does increase the Max Cog size.

My 50/34 cranks take a capacity of 16
The RD-6700-A GS has a capacity of 40
40-16= Leaving capacity available for the cassette not to exceed 24
With a Roadlink could actually run 11-34 (23 capacity) and still be under the Shimano capacity spec.
I've not purchased a Roadlink, but it is an option should my chicken legs require additional help.
BTW - their website makes great reading!

All the best

Barry

If you are even contemplating running over 30t, Davet has already given you the answer... get a 9 speed MTB rear derailleur. If the setup was good enough for cyclocross it is probably good enough for you.

John

John,
This is really about me learning understanding what is going on before I dive in. DaveT's post states 9sp MTB RD and 11-36 cassette but is that cassette 10SP or 9SP. I suspect 10sp but you know what happens when you "assume"!

I don't like to blindly take internet solutions. I read, digest, understand, and hopefully post a useful summary of any additional info I found along the way.
It is not my intention to ignore DaveT's solution, I just wish I understood it better. Sounds like a 9SP RD is being asked to deflect further in order to achieve 10SP, because there are 10 steps in the 6700 Brifter..... OK.

Also, I'd like to retain an Ultegra RD on the bike and found a way to do so while exceeding my original wish for 30T.

All the best

Barry

I have been running a 12-30 10s cassette with my short cage Ultegra RD since 2014, probably 31,000 miles so far with this configuration. It works fine, have to screw in the B-screw. But I would definitely not exceed 30 with it.