Why build a custom cassette?

Shimano in general make high quality bicycle components, but unfortunately the main focus of their marketing and design is toward either road or mountain biking. So for bicycle tourists like us some of their parts just miss the mark.

One example is the range of cassettes available. Road cassettes are geared on the higher side with close ratios, and mountain bike cassettes are geared lower with wider ratios. The bicycle tourist needs a bit of both. Close ratios are nice on the flat so that you can fine tune your cadence to ride as efficiently as possible. Very low gears are important to ensure you can winch your loaded bike over big climbs. Very high gears are not so important if we are travelling loaded.

A standard mountain bike setup with a triple crankset and 11-34 cassette will provide ample gear range, but the jumps between gears on that cassette are not very close. This means that on a challenging day where you are facing headwinds, false flats or lethargy it can be hard to get comfortable, and I find myself constantly switching between two ratios that are either side of what would be ideal.

There is a solution. Certain models of Shimano cassette lend themselves to modification. In particular, the Deore series of mountain bike cassettes, codenamed HG61, can be mixed and matched easily as each sprocket is full sized and engages with the splines on the freehub. Most of the sprockets are riveted together, but these rivets are easily removed to separate the cogs, as will be revealed later. Higher spec casseettes such as XT are not suitable because to save weight they feature an inner carrier to which the cut down sprockets are mated.

When I’m touring I don’t really need a high gear at all. Once my speed exceeds 30kmh on a downhill I’m happy to roll and enjoy gravity. So those 11, 12 or even 13 tooth sprockets are useless.

On an ebay whim a while ago I purchased a 12-36 HG61 cassette. I can’t even remember why. To make this cassette useful I decided to purchase another HG61, with 11-34 range and mate the two together to create the touring cassette of my dreams (I know I could have just purchased one from Harris Cyclery, but they don’t ship to Australia). The last and smallest sprocket needs to have an integrated spacer, so I also bought a Shimano 9 speed compatible Miche 14 tooth “first position” sprocket.

So this is my selection of sprockets:

12 – 14 – 16 – 18 – 21 – 24 – 28 – 32 – 36

11 – 13 – 15 – 17 – 20 – 23 – 26 – 30 – 34

and a 14 first position sprocket

This provides many options for customising my selection of gear ratios. For example I can go for very close ratios at the top end and then a few bailout gears for steep hills:

14 – 15 – 16 – 17 – 18 – 20 – 23 – 26 – 32

or another one biased more towards higher gears if you are travelling very light:

12 – 13 – 14 – 15 – 16 – 18 – 21 – 24 – 28

or an all round low geared cassette if you expect constant hill climbing:

14 – 16 – 18 – 20 – 23 – 26 – 28 – 30 – 34

The only real downside to modifying these cassettes is that the Hyperglide ramps that make shifts smoother are placed in staggered positions across the cassette to allow the chain to easily move between sprockets. By replacing sprockets we are going to muck up this arrangement. If you aren’t overly concerned with super smooth shifts this can be tolerated. But there is a workaround.


15 thoughts on “Why build a custom cassette?

  1. Steve

    Right at the end, you wrote: “If you aren’t overly concerned with super smooth shifts this can be tolerated. But there is a workaround.”

    What is the workaround?


  2. Steve

    Ah! I found the workaround here: https://fatseas.com/?page_id=192


  3. dave

    Thanks for your article,
    I have been frustrated, by lack of cluster ranges tuned for long mountian climbs..i.e alps.
    Last year, fitted 12-34 mountain bike cassette to road bike for french alps tour. ( i wanted to keep my 53/36 chain ring). It worked really well, except was frustrated by large gaps in gears at the lower gear range. Like yourself, I dont use the 12 or 14 sprockett. Will follow this up.
    Many thanks for your innovative thinking.


    • Paul Aguilar

      dave: “I don’t use the 12 or 14 sprocket.”

      During your customization endeavors have U found position 1 sprocket with more 14 teeth?


  4. Thank you for your very good advice,changing ratios due to my age! Geoff, Australia.


  5. Russell

    Great article. With the reduced availability of 9 speed drive train components how would this process work with 10 speed cassettes


    • I haven’t tried it with 10 speed cassettes but it should work provided you can find cassettes that have individual sprockets (even if they’re riveted together) rather than smaller ones attached to a carrier.


      • PJ Foltz

        I just did this with two Shimano 105 11-speed cassettes. I kept the three largest sprockets riveted together and built the rest to be close ratio. Of course I had to keep the 11T-12T locking combo, which leaves quite a gap to the third sprocket, but the shifting seems OK going up and down (I ease up on the power when shifting.)


  6. Morten Knudsen

    Interesting – how does the MIche prockets shiftramps intergrate with a Shimano casette?

    14,15,16,17,19,21,24,28,32,36 would be my ideal 10-speed casette for alpine adventures – mated with a medium cage SRAM MTB deraillure.

    Im considering swapping out the 11t, 13t cogs on a XT/XTR 10-speed 11-36 casette with CS6600 cogs. The CS6600 is the only shimano 10 speed casette with a 1st 14t cog, I would need the following cogs:

    14t Y-1ZD 1400D
    15t Y1Z8 1500D – i dont think that the 15t XT/XTR (Y1YR15000) cog shiftramps would intergrate well.
    16t Y1Z8 16000
    17t Y1Z8 1700D or the stock Y1YR17000 – i’d gues that neiter would intergrate perfectly.

    The 6 cogs from 19t to 36t would be the clusters from the XT/XTR casetttes.


    • Jim W

      I’ve done something similar to Morten K’s plan.

      On 10 Speed, I’ve combined the bottom of a cs-6600 14-25 with the top of a CS-M771 11-34 cassette.
      I used 14,15,16,17 from the cs-6600 and 19,21,23,26,30,34 from the cs-m771

      One series of the HG ramps are well aligned in between the 17t to 19t cogs.
      I have not noticed any oddities in shifting.

      It should also work to make the same combination with the top of a 11-36 cassette at the 19t cog like you are planning since the top of the 11-34 and 11-36 only change after the 21t cog.

      Another mod I’ve done to the CS-M771 11-36 cassette is to swap the 11t and 13t cog for a Miche 13t first position and 14t cog. This did require a new lockring on the 13t.

      This mod gives me 3 cogs with a 1 tooth change.

      However, shifting in between the 14t and 15t does seem to be “clunklier” it works, but is not as smooth.

      Good luck!


  7. Tom in MN

    Shimano HG50-9 series of cassettes also have full size cogs and 5 to 7 of them are held together with three rivets.

    The SRam PG-970 series also has full size cogs and the ones that are held together are connected by a single screw (1.5mm hex cap head) so they are much easier to take apart. The Road and MTB versions have different type spacers and cog shapes, but you can trim some bumps off the ones you put between cogs of different types easily. I even managed to reuse the screw — you have to include the cog that is threaded in the right place. Road and MTB cassettes also have different numbers of cogs attached so you have a couple of choices of threaded cogs and crew lengths. I think it’s related to the ones with 11t cogs needing a special cog next to it, so that cog is also free.

    Note that only 11t cog lock rings are different, the 12t and up are all the same. But as you found out you do need a cog with matching teeth for the lock ring. I kept my 12t cog as the smallest to avoid having to buy another end cog. If you can arrange to buy one of the cassettes with the smallest cog you want to use on your custom cassette you are all set.


    • Thanks for the additional data Tom! I haven’t made any more custom cassettes since the original one in this article which is still going strong. But nice to have other options when I get around making another one.


      • Tom in MN

        Happy to help with your useful page.

        I’m also doing a 10 speed one and found that Shimano CS-HG500-10 cassettes are all separate cogs (105 and HG62 have carriers for the largest cogs on the two other cassettes I have). There are some extra details on 10 speed cassettes. The largest cog and the spacer that goes with it are special as the cog has an offset and the spacer is not flat, to help with fitting 10 speeds on what was originally a 9 speed freehub. So you can’t plan on using both largest cogs from a pair of cassettes. There are also spacers with radial arms between the largest cogs that you will have to orient correctly when you put your cassette on the freehub to keep the spacer arms between the spider arms (if you can) on the neighboring cogs. And it appears the smallest two cogs must stay together (at least for 11t and 12t smallest cogs, which both had neighboring 13t cogs on the cassettes I used — and they were slightly different).

        The rivets ended on both 11-34 and 12-28 cassettes at the 15t cog, which means that they had different numbers (8 and 7 respectively) of cogs riveted together. My first thought was that they were using the same 15t cog with countersinks for the rivet heads on both cassettes, but they have different teeth orientations to align with the neighboring cogs correctly. Thus you may be able to try different cogs with the same numbers of teeth to see if it affects the quality of the shifting. I try to keep sets of cogs from the same cassette together to help the shifting.


  8. barney

    I have done the same, as an older cyclist pottering in hilly terrain I have a few widely spaced high gears and more close spaced low gears. Never noticed any significant difference in the gear changing but really good to have a number of low gears for hills.


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