Sunday, October 16, 2022

Shimano HG vs Microspline vs Road 12 Speed vs SRAM XDR Freehub Body

Nowadays, there are so many different types of freehub bodies, mainly due to different manufacturers and also different cassette requirements.

The most common one is the HG spline standard, or the Shimano spline that has been in use since 8 speed cassettes. In fact, 8/9/10 speed cassettes use the same HG spline. 11 speed cassettes have the same spline pattern, just that it is 1.85 mm longer.

Then, there is the SRAM XD and XDR standard. This are radically different from the original HG spline, as there is only a short spline section. It is originally designed for MTB cassettes with a small 10T sprocket. I first used it on the Fnhon DB12 wheelset, when I changed to the SRAM Force 10-36T 12 speed cassette.

There is also the Shimano Microspline freehub, for Shimano 12 speed MTB cassettes. I have not had the chance to use a Microspline cassette on my own bike, but this is the Shimano alternative to the SRAM XD/XDR freehub.

The most recent addition to the freehub collection is the new road spline for Shimano 12 speed road cassettes. Once again, another design that is different from existing designs.
Microspline and XD/XDR can accommodate cassettes with a small 10T sprocket, which is useful for a wider gear range without going to even bigger sprockets at the other end.

The new Shimano road spline cannot have a 10T sprocket, as it is designed just to fit 12 speed Shimano road cassettes with a small sprocket of 11T.

From left to right: Microspline, standard HG (11 speed version), and XDR freehub bodies.

HG spline on top of Microspline. The diameter of the Microspline splines are smaller, while the length is also shorter, all for the 10T small sprocket.

XDR freehub on top of the Microspline. Note that the XDR only has a short spline, and a threaded section for the XDR cassette to be screwed onto the freehub body.

HG spline next to the Shimano 12 speed road spline, on the Dura-Ace R9270 wheelset. Similar length.

Microspline on the left, road 12 speed spline on the right. Looks similar, but not quite the same.

Splines on the Microspline freehub are of equal height, unlike the ones on the road 12 speed spline. Microspline freehub is also shorter.

Close up of the aluminium Microspline freehub. There are many splines and are relatively tall to prevent gouging by the steel sprockets.

If you try to put a road 12 speed sprocket onto the Microspline freehub, you will see that the Microspline diameter is smaller and does not fit.

After reading through this article and seeing the pictures, you should have a good idea how each one of them looks like, and what cassettes are compatible to it.


  1. Hi Steve, could you advise which type of freehub body should we get to be future-proof (regarding road freehub)? It's a bit unclear because compared to HG spline, the new Shimano 12 speed road spline lost backward compatibilities with 8-11 speed cassette while the smallest sprocket is still same 11T. For XDR, at least it loses compatibilities but allow smallest 10T sprocket. On the other hand Campa has a 13 speed hub which seems to be compatible with existing 10-12 speed cassette but not sure how that works. Do you think Shimano and SRAM will change hub design again for 13 speed and 9T that will not be backward compatible?

    1. You are right that each of the 3 manufacturers have their own freehub design that are not interchangeable. It is hard to say which one will dominate, as each has their benefits. Most likely we will see all of them still existing in the future.
      In this case it is more important to find a hub that has interchangeable freehub bodies. This will allow you to change the freehub bodies depending on the cassette you want.
      Examples are DT Swiss and Novatec which has modular freehub bodies for easy swapping.

  2. Thanks for the review! Do you know if the spacing between a Shimano MTB 12-speed cassette is the same as a Shimano road 12 speed? I ask as I want to use a road wheel and cassette with an MTB shifter.

    1. I think the spacing might be similar. In any case, what components are you planning to use?

  3. It will be for a 1x TT bike, I want to use:

    1. Microshift end bar for Shimano MTB (12speed)
    2. Dura ace 9100 Rear Derreilleur (11speed)
    3. Dura ace 9200 11x30 cassette (12speed)
    4. Dura ace/XTR chain (12 speed)
    5. And a 1x crankset

    What do you think?
    Am I crazy? xD

    1. The shifter and rear derailleur is unlikely to work properly, as the cable pull ratios are very different between MTB and road.

  4. The rear derailleur should work fine as it can move to any position, its position is only determined by the shifters.
    As long as the 12 speed MTB and Road cassettes have the same exact total width and center-to-center cog spacing then it should work fine.
    But I have not been able to confirm their widths :S

    1. You can try it, but I can assure you that the MTB shifter will not work with the road RD.

    2. Too much money to be wasted to try and for it not to work.
      Path Less Pedaled tried this and it worked fine, you can check his youtube channel.

    3. Can't find it on his channel. Can you share the link? Interested to know exactly what he used.

    4. Here you go:
      Check on the comments too, I asked him about that setup and he answered me with some details.

    5. I probably misunderstood your previous comment, as I thought you were going to use an indexed Microshift 12 speed MTB shifter.
      If you are using a friction type shifter instead, then it will work. A friction shifter does not have specific speeds as it can shift anywhere from 2 to 12 gears or more, as long as the cable stroke is long enough to cover the whole range from Top to Low.

  5. Crabs!
    I might have to keep di2 on that bike or go with 11 speed mechanical 🤔