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Been thinking about upgrading my drive train, however, I'm not sure if I've fully understood the compatibility part and wanted to get some more clarifications. Currently have an Advent X (10spd) and my hub is a Shimano FH-TX505 with HG freehub. My questions that I had are:

  1. Can a 12spd (11t or higher) fit on a HG freehub? On the Shimano website, it say 8-10spd, 11spd mtb. However, some cassettes such as the Garbaruk 12-Speed HG Cassette, state they work with the HG hub?

  2. Can you change the freehub? Again, the wheels I have use the FH-TX505 hub. I know there's a specific compatibility between which hubs can actually be converted but I couldn't find much info on this specific one. My guess is no but I'm really not too sure. Oh, the hub is also (not too sure) QR 10x135, not sure if that matters. Side note: I mainly care about this because I was hoping to get a speed lower than 11t (10 or even 9) as I have been toping out a lot. I guess upgrading from 30t to 32t chainring might be another option...

  3. If Q2 is no, then is there anyway for me to get a wheel set with XD or micro spline freehub? I've been looking around for wheel sets for QR 10x135 but the ones I've seen all use HG.

Thanks!

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Hyperglide is the freehub format that Shimano used for its 9 through 11 speed mountain bike and road hubs. However, when Shimano launched its 12s MTB, 1x drivetrains had become almost universal on MTBs, and they may work best with 10t cogs. The Hyperglide freehub body has too large a diameter to accommodate a 10t or smaller cog. Thus, Shimano went to Microspline; that freehub body is truncated at the end, a bit like SRAM's XD and XDR bodies or Campagnolo's N13 freehub body.

Some third party 12s cassettes can fit to Hyperglide freehubs. These can only accommodate an 11t small cog.

In principle, Shimano might be able to design a microspline freehub for that particular hub. However, it might not be economical for them to do so if demand is too low, or it might be impractical due to the dimensions of the hub. The hubs on many higher end wheels have had microspline freehubs released, but again, not enough commuters might want to pay extra for microspline hubs. It's also worth considering that it's often cheaper to just sell the bike and get a new one with the desired spec.

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First, it seems as your goal is for a higher ratio on the top end of your gearing so that you won't as easily "spin out"--require such a high RPM to maintain or gain bicycle velocity that it's physically impossible to maintain or achieve such a high RPM. The fact that you are using a 30 tooth chainring infers that you are on a mountain bike. That it has a QR 10x135mm rear hub infers it is an older mountain bike or some form of hybrid bike. In either case--and for many other compatibility and cost reasons--moving to a 12 speed cassette that may have a 9 tooth high gear sprocket to achieve that higher ratio will not work because a 135mm spaced hub has no room for over 11 cogs. As you realize, you require a MicroSpline free hub for 12 speed Shimano cogs and your current hub is not likely to be compatible for one. There's no point in researching that due to the incompatible spacing to begin with. Note, as well, that going to an 11 or 12 speed rear will require a new shifter and rear derailleur since a 10 speed shifter has only enough detents (9) for 10 cogs and a 10 speed derailleur is not directly compatible with 11 and certainly 12 speed systems. There is quite a bit of expense there, even if you had a compatible hub and frame spacing, when a bigger chainring will achieve the goal as well.

The easiest--really the only-- way to get a larger, faster top end gearing ratio is to simply replace your current 30 tooth chainring with a 34 or 36 ring. Thirty-two tooth ring won't achieve much gain in your high ratio. Probably wouldn't even be noticable.

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  • The issue that I'm currently wondering about is how a 34t chainring would affect the climbing. I won't lie, I really like the climbing for that 30x48t, but to move to 34t chainring would require a 51/52t low gear to maintain a similar gearing ratio? But you are correct, doing so would require a whole drive train upgrade. I guess on a side note, I could always move this drive train to my sister's bike which is using a 3x8 currently.
    – dwang040
    May 21, 2021 at 0:58
  • @dwang040 Do you use the 48t cog a lot? More than the 11 or 13t on the other end? A 34/48 (.708) yields a slightly lower ratio than the 30/40 (.750) combo, which is likely your second to lowest gear if you have the Advent 10s cassette (11-48t). My preference would be to have a little more top end speed, especially if, at the low end, I would find myself in a gear that was somewhere in the middle of my current low and second to low gear. To me that's a fair trade off. I run 2x cranksets (34/24 & 38/28) with 11-36t cassette and enjoy the wide range. This is another option you might look into
    – Jeff
    May 22, 2021 at 6:14
  • I primarily use the 11 - 21t range the most. But to be fair, I haven't had the chance to experience a lot of climbs (haven't gotten a chance to go try out the mountain trails). For now, what tends to happen is that I bike down to a nearby trail so like 90% of the journey is road and the trail itself is flat with small climbs. Where that 48t shines is on the journey back where I'm tired and I have to climb up a pretty steep hill to get back home. I'm usually in the 30/40t or 30/48t. I could definitely get away with 30/40t with more training so maybe 34/48t won't be too bad.
    – dwang040
    May 23, 2021 at 15:35

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