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I have a Giant 2013 TCX Advanced. It has a Rotor 3DF, 36/46 Crankset and a SRAM XG1190 11x28 cassette. I'd like to swap the cassette for an 11-40 or 11-42.

The guys at Wolftooth said: "..derailleur does NOT have enough capacity to handle an 11-40 cassette and a double chainring. You will have to be careful to not use small/small and large/large gearing combinations.."

Can I simply buy a new long cage derailleur, such as Sram Unisex's NX 1x11?


Edit:

Thanks David and..Ouch! Never realised that! So, to keep it relatively simple (and less expensive): my best choice to get to at least 1:1 is to replace the 36 crankset with, say, a 32 and the cassette with an 11-32? ...Again using the roadlink from Wolftooth? Do I need to replace the short cage? Can I replace the 36 with a 30... (and install the 11-32 cassette?).

  • Note that no answer so far has touched on the Wolftooth roadlink. What you want is impossible according to SRAM, but made possible using the aftermarket Wolftooth component with various downsides. Like Wolftooth said: Since your rear derailleur does not have the total capacity to run an 11-40 cassette you have two options: too long chain, which means the derailleur can no longer stretch the chain near small/small or a too short chain, which means you can't easily shift into big/big and tear off your read derailleur if you force it. – StefanS Apr 2 '19 at 9:48
  • I'm not sure how to answer these posts using your site...Sorry if this is not the right way! – huckfinn Apr 2 '19 at 10:43
  • Anyway: .."Normally there is a 16 tooth difference between rings on compact cranks...": Does it mean I can swap the 36 for a 30 and install an 11-32 cassette? Would this be within the total capacity of my rear derailleur? – huckfinn Apr 2 '19 at 10:46
  • huckfinn - what kind of riding are you doing? Are you happy with everything else on the bike except the gearing? Just trying to get an idea of the larger picture. – David D Apr 2 '19 at 16:11
  • Bike's great when keeping up with the pack. But in the region where I live we have large amounts of climbing too (read Turini and Madone....) and a ratio closer to 1:1 would be great! – huckfinn Apr 3 '19 at 15:43
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You can't just get a derailleur and cassette to make this work the way you want. The components are designed as part of a system with parts that are designed to work together, at least according to SRAM.

You will want a rear derailleur that matches your SRAM Red shift levers.
According to page 2 of this chart:
You can get gearing of 11-32 or 12-32 with a range of front chain ring sizes if you use the mid length arm of the SRAM Red 22 rear derailleur. This would be a derailleur and cassette purchase (I'm assuming your bike came with a short arm rear derailleur) that would get you closer to your goal, but not all the way.

To get to 11-40 or 11-42 and have all the parts match you'd have to go with a different parts group.
According to page 3 of the chart linked above the Force 1 or Rival 1 shifter, long cage derailleur and cassette will go to 42.
You'll also need a longer chain.

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    I believe that the Sram 1x groups are not compatible with a front double chainring. Really 40+ tooth cassettes are designed for a 1x system. – Argenti Apparatus Apr 1 '19 at 23:44
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As David D said in his answer, mixing and matching SRAM components isn't really possible.

The 46/36 crank on that bike is a bit unusual (to me at least). Normally there is a 16 tooth difference between rings on compact cranks (52/36, 50/34, 48/32 etc.) I think the rotor cranks have a 110mm BCD so they should be able to take a 34 tooth ring.

a smaller small chainring combined with a 11-32 cassette will drop your lowest ratio from 1.28 to 1.06, and should stay within the total capacity of your rear derailleur.

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    46/36 is common on CX bikes. With the 110mm BCD a 34 or even 33 teeth small chainring is possible. – Michael Apr 2 '19 at 8:14
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To answer your follow-up question: So your main goal is to get easier gears? As far as I’m aware a 1:1 ratio with your SRAM components is not officially possible.

The smallest chainring you can get for your crank with a 110mm BCD has 33 teeth. The biggest cassette you can get for your rear derailleur (largest sprocket 32t) is an 11–32t. If you keep the large 46 teeth chainring you’d already exceed the rear derailleur’s capacity of 32 by two teeth.

So officially a 44/33 (or 44/34) chainring combination and 11–32 cassette is the closest you can get to 1:1 ratio.

With a Wolftooth Roadlink you could go for a 11–34 cassette and a 42/33 chainring combination.

Another option are the so-called “super-compact” or “sub-compact“ cranksets which allow you to use 30 teeth chainrings. See these articles for some examples: https://www.bikeradar.com/road/gear/article/super-compact-chainsets-the-next-big-thing-for-road-cyclists-48974/ , https://www.cyclingabout.com/low-climbing-gears-road-bike-crankset/

Be aware that for good results with super compact cranksets you have to move the front derailleur downwards which might not be possible.

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  • sub-compact” cranksets: you mean the Praxis ones? + so you think a Roadlink with 46-33 combined with an 11-34 cassette might do the trick? – huckfinn Apr 2 '19 at 14:18
  • Oh, apparently “super-compact” is the correct term. I’ve edited my answer. – Michael Apr 2 '19 at 15:29
  • Allright!! So: a very "simple" super-compact AbsoluteBlack 46/30 + 11-30 cassette? – huckfinn Apr 2 '19 at 15:35
  • That would do it, right? – huckfinn Apr 2 '19 at 15:36
  • Not enough capacity. The SRAM Red 22 rear derailleur only has 32 teeth capacity even in the medium version. 46-30+30-11=35. 44/30t chainrings and a 12–30t cassette would be OK (44-30+30-12=32). I don’t know why they are that limited, with Shimano even the short version (35t) would do it. – Michael Apr 2 '19 at 16:28

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