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Can an Ultegra or 105 short cage RD handle a 30T ?

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    There's been 25+ years of 105 setups. It will change depending on which 105 you're talking about. In any case, just go to shimano's website and read the data sheet.
    – Batman
    Jun 7, 2015 at 11:46
  • I'm not a Shimano person, but I've heard some Shimano derailleurs have the capacity stamped on them. Does it?
    – andy256
    Jun 7, 2015 at 13:41
  • In most cases a 28T shimano mech will run a 30T rear fine.
    – DavidG
    Jun 8, 2015 at 11:41
  • Shimano has been very good about stamping the model number on their components over the years, so it is easy to get that number and find just about anything you'd want to know. On rear derailleurs, the number is usually stamped on the side of the parallelogram facing the wheel, and will read something like "RD-5800".
    – ichabod
    Jan 31, 2020 at 16:53

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As I said in a comment, there are 25+ years of 105 and Ultegra (well, ultegra was called something else back then, but the line has been around for quite a while), so you need to find the right 105/Ultegra you're talking about.

You can find the Product Info at this link.

In 11 speed: The Ultegra RD-6800-SS and 105 RD-5800 SS both have a 28t max. Thus, Shimano doesn't recommend you run a 30t with a short cage. The RD-6800-GS and RD-5800-GS both have a max of 32t.

In 10 speed: The 105 RD-5701-SS has a 30t max.

Note that Shimano has mucked up cable pulls between 10 and 11 speed road, so you can't just put a 10 speed RD in a 11 speed system.

Note that also there may be several RD's under the same group under the same year or # of speeds (e.g. in the Sora case), so you need to look up the particular RD you want to use.

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  • I'm using a 2005 or 2006 Shimano 105 RD-5600. It is officially rated 27T maximum sprocket. I'm using a 28T and it shifts perfectly. Just wondering if it could handle a 30T.
    – Coleman Morrissey
    Jun 8, 2015 at 12:39
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For the 5800, short cage can only take 28t but I wonder this too after seeing this.

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  • Thanks. Looks like he loosened the B tension screw to lower the jockey pulley and is able to have a 32T lowest gear.
    – Coleman Morrissey
    Jun 14, 2015 at 8:00
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It's worth mentioning that most max tooth specs are on the conservative side. Meaning that if you put your drive train into inappropriate combinations you would expect problems if you used a cog bigger than recommended. If you already know not to use the gear combos of "little cog in the front, little cog in the back," and, "big cog in the front, big cog in the back," then you could squeeze a bigger rear cog. Of course this is not recommended, but it's fun to know and play around with.

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I currently have a 105 1x10 setup with a 42t front chainring and have used 11-34 and 11-36 Deore cassettes.

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  • But what size is your rear derailleur?
    – DavidW
    Jan 31, 2020 at 13:24
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    Also, derailleur capacity is the amount of slack the derailleur can take from both the front chainring difference and the big-small cog difference. In a 1x, you will naturally be able to handle a bigger cassette than in a 2x setup.
    – Weiwen Ng
    Jan 31, 2020 at 14:20

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