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34T to 36T cog for Ultegra CS 6700

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34T to 36T cog for Ultegra CS 6700

Old 07-23-21, 09:05 AM
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ganner
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34T to 36T cog for Ultegra CS 6700

I started cycling again after a long time away. But I'm doing shorter cycles and more hill climbs.

My existing bike has a full Shimano Ultegra CS6700 groupset.

I'm running 52T/39 crankset with 11-28T cassette. Without spending too much money I'm looking at SRAM 1070 11-36T cassette or 11-32T.

Anyone knows if it's possible to fit either or has done it before? With a roadlink and perhaps new chain? My RD cage is most likely a short cage and not the GS version. I can't see any marking on the RD anything short of taking it apart.
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Old 07-23-21, 09:25 AM
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No, it won't work. It's way over the max cog spec of the derailleur and it's capacity. Find an 8 or 9 speed mtb derailleur and use that. If you want to use the 11-36 cassette you will obviously need one that's spec'd for a 36t big cog AND has a capacity spec that is =/> 38. A 10 speed mtb derailleur will NOT work.
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Old 07-23-21, 10:18 AM
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I've done what cxwrench recommends (8 or 9 speed MTB RD) on several bikes and it works great with both 9 and 10 speed road shifters. 8 or 9 speed Shimano MTB rear derailleurs are easy to find, (usually) not expensive on EBay, and easy to install and adjust. Like the OP mentioned, a new, longer chain will probably be needed too. All of this are pretty simple DIY's - YouTube is your friend if you've never done an RD installation and basic adjustment.
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Old 07-23-21, 11:16 AM
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An 11-36 is going pretty far beyond the design specs for an RD-6700-SS. With hanger extenders and b-screw shenanigans or whatever you might be able to force it to clear, but even if you do, you'll likely have questionable shifting, and you'll be exceeding the derailleur's wrap by quite a bit (which forces its own compromises that range from annoying to dangerous).

I'd go with an 8-speed or 9-speed Shimano MTB derailleur. They're compatible with pre-2015 10-speed Shimano road drivetrains.
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Old 07-23-21, 07:01 PM
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Thanks for the answer.

How about 11-32T?

​​​​​​Would it work?
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Old 07-23-21, 07:03 PM
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Originally Posted by Camilo View Post
I've done what cxwrench recommends (8 or 9 speed MTB RD) on several bikes and it works great with both 9 and 10 speed road shifters. 8 or 9 speed Shimano MTB rear derailleurs are easy to find, (usually) not expensive on EBay, and easy to install and adjust. Like the OP mentioned, a new, longer chain will probably be needed too. All of this are pretty simple DIY's - YouTube is your friend if you've never done an RD installation and basic adjustment.

Thanks for the respond. So a 9 speed derailleur would work with a 10 speed system groupset? I'll have to get it brand new if it possible. Ebay shipping would make it a little expensive for where I live
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Old 07-23-21, 07:20 PM
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Originally Posted by ganner View Post
Thanks for the respond. So a 9 speed derailleur would work with a 10 speed system groupset? I'll have to get it brand new if it possible. Ebay shipping would make it a little expensive for where I live
It works with my wife's 6700 (6703) shifters. I've used a variety of 8 and 9 speed Deore XT and other RD's with 9 and10 speed shifters. I've never had any problems with an 34 large cog. Some will handle 36 easily, some won't (in my limited experience).
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Old 07-23-21, 07:25 PM
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Shimano Deore M591 is a popular choice, still current production AFAIK.
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Old 07-23-21, 10:35 PM
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Seems like sourcing for a compact crank would make more sense now.

Any recommendations?
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Old 07-24-21, 01:26 AM
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The crankset is the better idea by a large margin anyways. Obviously a compact 6700 crank will match the aesthetics of the rest of the group set the best if that's something you care about. Tiagra 4700 is current production and intended for 10sp, and will be a straight drop in for your current bottom bracket.
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Old 07-24-21, 01:39 AM
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Originally Posted by cpach View Post
The crankset is the better idea by a large margin anyways. Obviously a compact 6700 crank will match the aesthetics of the rest of the group set the best if that's something you care about. Tiagra 4700 is current production and intended for 10sp, and will be a straight drop in for your current bottom bracket.
Thanks.

Do I need to change anything else? Chain? Also is FSA or rotul or something suitable?
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Old 07-24-21, 04:45 PM
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Originally Posted by ganner View Post
Thanks.

Do I need to change anything else? Chain? Also is FSA or rotul or something suitable?
I'd probably do the chain, just because it's probably time, and it'll be too long on a compact double anyway.

As far as compatibility goes, you can pretty much pick whatever compact double you like the looks and gearing of... aftermarket cranksets are almost all designed with the assumption that they'll be used with Shimano drivetrains. (Plus if it works with Shimano's persnickety front shifting, it'll work on anything.) You'll almost certainly need a new bottom bracket, which you should buy when you buy the crankset, unless you find one that takes the same BB you've already got.

48/36 gives you a ~34" low and a ~118" high gear. 46/34 gives ~32" and ~114" respectively, with your existing cassette, and you're only exceeding the chainwrap spec by one tooth, so no worries. If your front derailleur is braze-on mount, the 48/36 will likely shift better, because often you can't get the front derailleur low enough to run tight with a 46T big ring. If it's clamp-on, I'd go 46/34 and trade a bit less high end for a bit more low. 48/36 cranksets are way more common, though.

--Shannon
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Old 07-24-21, 07:26 PM
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Thanks for the detailed explanation.

The 6700 has been through alot with me but it seems like it might be time to switch it out.

I might go with the 105s R7000 fullset. It's going to come out of my next bike budget. But it would be easier.
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Old 07-24-21, 09:06 PM
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Originally Posted by ganner View Post
I might go with the 105s R7000 fullset. It's going to come out of my next bike budget. But it would be easier.
I'm confused...

How is changing an entire groupset easier than changing just the cranks? Not even considering the factor-of-4 cost difference, I can do a crankset swap in less than an hour and a beer or two, and a complete rebuild takes all day and at least a six pack.

I mean, if'n you wanna upgrade the whole bike, it's your bike and your bread, and building bikes is rad, so go for it, but if all you want is wider range gearing, change out the crankset, BB, and chain, and ride happily off in to the sunset.

--Shannon

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Old 07-24-21, 11:57 PM
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Originally Posted by ShannonM View Post
I'm confused...

How is changing an entire groupset easier than changing just the cranks? Not even considering the factor-of-4 cost difference, I can do a crankset swap in less than an hour and a beer or two, and a complete rebuild takes all day and at least a six pack.

I mean, if'n you wanna upgrade the whole bike, it's your bike and your bread, and building bikes is rad, so go for it, but if all you want is wider range gearing, change out the crankset, BB, and chain, and ride happily off in to the sunset.

--Shannon
my part of the world is under lock down at the moment. and we are not sure when it would be lifted. strange enough we can cycle or jog individually. to source for different parts i.e. the crankset or chain ring, chain, bottom bracket and figuring it out if it would work after buying them is a risk to me. i would lose shipping fee if i get them wrong. if i buy them 2nd hand, i have to resell them and lose some. the coordination takes a lot of effort/time and could cost more than half as much as a new groupset. Furthermore, I just discovered that my sti shifters and chainring has some rust on them. i just bought some chemicals and lube to try to salvage it. i don't have the tools at home and bike shop these days are running 150% with no stock on whatsoever item you want. bike shops are also just telling small revenue customers to basically f off as well. this is the same for golf shops and tennis shops.

all in all, a new groupset would work seems to be a better option for me now.

let's say if i'm still interested in a crankset. can you get me know exactly which crankset and chain i should get? my current bottom bracket is sm bb6700 (seems like a screw in outboard type 68mm, frame is argon18 krypton kr36), can i reuse the bottom bracket?

Last edited by ganner; 07-25-21 at 12:06 AM.
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Old 07-25-21, 01:20 AM
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Originally Posted by ganner View Post
Let's say if i'm still interested in a crankset. can you get me know exactly which crankset and chain i should get? my current bottom bracket is sm bb6700 (seems like a screw in outboard type 68mm, frame is argon18 krypton kr36), can i reuse the bottom bracket?
Outboard bearing bottom brackets are not something I know much about, so I can't really help you there. I usually just assume that different cranksets require different bottom brackets, and if they don't, you got lucky.

As to chains, I've been using SRAM for years, but I've never noticed a brand difference that's worth paying real money for. I have worked on a few bikes that worked better with a particular chain, but that's never been correlated to price, brand, or anything else, and isn't very common in any case. It's one of those things that, if it bites you it bites you, and if it don't it don't. Get the one that matches the number of cogs in your cassette, that you can get and afford, and ride away.

But, yeah, you're probably gonna need a new chain. Rule of thumb: if you're making any major changes to the drivetrain, you're gonna need a new chain.Sometimes you get lucky and your old chain will work. But don't count on luck. Buy a new chain. Worst case, you've got a spare.

--Shannon
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Old 07-25-21, 05:21 AM
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[QUOTE=ganner;22156545]all in all, a new groupset would work seems to be a better option for me now./QUOTE] I would not discourage this if it's in your budget and you can find one. There would be several advantages over your current set up. Select the 50-34 crank and the 11-34 cassette. The smaller cassettes may not work if your wheels aren't designed for 11 speed. FWIW, your existing 6700 bb is compatible with the newer stuff but complete groupsets would include the bb. They are cheap so don't let the bb distract from whatever path you choose.
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Old 07-25-21, 06:25 AM
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wheels are not designed for 11 speed. but the r7000 and r8000 11-34t cassette fits 10 speed hubs.

i just discovered that i've been cycling on cs6600 12-23T not cs6700 11-28T as i though it was. some shop i have been going. explains why 7% gradient feels impossible.
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