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I have a Shimano Ultegra RD-6700 rear derailleur with a 10 speed Shimano 105 5700 11-28 cassette and Shimano R565, 50/34 (compact) up front.

I would really like a larger gear for climbing. Can I go to a cassette with a larger than 28t that would not require a new derailleur?

I see that in Shimano 105 5700 cassette series only goes up to 11-28, but the Ultegra 6700 10 speed goes to 12-30. Is there another cassette that I could use that goes to -32t?

How can I tell if I have the RD-6700-SS (capacity 33t) or the RD-6700-GS that has the 39t capacity? It only has "Shimano RD-6700 Japan VIA" stamped on the back. It's the one that came with my 2013 Trek Madone 4.5.

I assume that I have to stick with a 10 speed cassette in any case. Are there any options beside the Ultegra 6700 12-30 that would fit?

Any advice is greatly appreciated!


EDIT: I measured the distance between the centers of the jockey wheels, and its about 6cm, so it looks like I do have the short version.

Is it possible to go from a 10 speed to an 11 speed cassette, like the Shimano Ultegra 6800 11-32, without changing the shifter? I realize that I would have to change the rear D to something like the Shimano Ultegra 6800 GS, which says it can handle up to an 11-32.

I didn't see any options for changing the the front chainrings, it seems like the 50/34 compact is the only one that fits this bike.

  • Have you looked at a smaller granny gear up front ? It may be possible to swap in a 46/30, or to look for a triple. My road bike is a triple with 26 tooth small and a 28tooth large cog, returning a ratio below 1. You could start using MTB cassettes and a MTB derailleur and get anything up to 42 or even 50 tooth in the sram line. – Criggie Jul 11 '17 at 7:30
  • You can find out the cage type of your RD by checking the distance between the bolts that hold the jockey wheels. Short cage is 6cm. – Carel Jul 11 '17 at 13:00
  • On my roadie, the shifter was originally an 8-speed Sora (RD3400 or something). At some moment, a serviceman installed the 10-speed Ultegra cassette, and the corresponding handlebar shifter, yet retained the derailleur. It worked fine for some time, then problems arised with switching to the 10th gear, which was useful on very rare occasions, but otherwise the whole combination ran fine for a season. – bipll Jul 13 '17 at 19:41
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Have a look at the spec sheet for the RD-6700. In the table in the table in the centre it says that that largest sprocket for the RD-6700-GS is 28 tooth - so I don't think the RD-6700-GS will help you.

Instead you might consider a Tiagra RD-4700-SS which can fit up to a 34 tooth sprocket.

  • 4
    Infuriatingly, RD-4700 uses a different actuation ratio, the same one as 11-speed road RDs. – Nathan Knutson Jul 11 '17 at 14:07
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There is a very handy gizmo that you can use with road derailleurs to increase the size of cog you can use in the back.

Wolf Components Road Link

I use it on one of my bikes to have a 11-32 rear cassette. The cassette spacing on Shimano 10spd is the same between road and mtb, so you should be able to just replace your current cassette with an MTB one.

You will still be within the safe range of the capability of your rear derailleur. Long cage Road derailleurs generally have 39t capacity, so 16+ 21 = 37. So you could even go to an 11/34 MTB cassette. You can safely go beyond the capacity of the derailleur if you avoid small/small gear usage, However, that's hard to do with a compact double up front.

Another solution that I think you might prefer is to switch to a smaller crankset up front. For most people 46/30 and 11/28 in the back makes a really good setup.

Unfortunately, 46/30 cranks are not the easiest thing to obtain, but that is changing with the popularity of "Gravel" bicycle components. FSA makes a nice 46/30 "adventure" crankset and you can get those chainrings with MTB cranksets like the Shimano 10spd XT double.

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To use older 10-speed Shimano shifters such as Ultegra 6700 with cassettes larger than 28t, you need to use a 9-speed MTB derailleur. You'll be able to handle cassettes up to the largest specified for the MTB derailleur (and likely a bit larger).

Shifting won't be as good as a full Ultegra 6700 drive train, but it will work.

  • True, I’ve used this to get a 11–34 cassette working with a Shimano 105 5800 groupset. The only issue I had is that the MTB rear derailleur has a relatively strong spring which requires more strength to shift to larger sprockets (make sure your cables are good and low friction). – Michael Sep 11 at 10:55
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You could look at SRAM cassettes (SRAM and Shimano components are compatible) for more options. The SRAM PG-1070 has a 12-32 version. Also note that you can use a mountain bike cassette if you want big sprockets (and the derailleur can handle it).

You'll probably need to change the derailleur if the total tooth change is more than your current one can handle - and you can use 10 or 11 speed. The 10 speed derailleurs have slightly chunkier jockey wheels than the 11 speed, but I've used a 10 speed derailleur with an 11 speed chain without any issues and an 11 speed derailleur will handle a 10 speed chain with ease.

The gear indexing is controlled by the lever, not the derailleur. So if you fit an 11 speed cassette and have a 10 speed gear lever, you will only get 10 positions - which won't quite line up with the cogs on the cassette. Unfortunately replacement brake/gear levers aren't cheap.

  • 11 Speed cassette requires 11 speed shifter, otherwise it will not shift correctly. – GLNN.LRSN Jul 12 '17 at 15:34
  • Indexing is a combination of both the shifter and built-in pull ratio of the rear derailleur. There are lot's of incompatible combinations in the Vendor/MTB/Road space. – Fred the Magic Wonder Dog Jul 13 '17 at 16:11

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