The new SunRace MZ 12-speed mountain bike groups takes a lot of the high end modern drivetrain tech, and brings it down a price notch. With a complete catalog of 12-speed wide range cassette options, including a massive 10-52, there’s something for everyone. Pair those with a SRAM or Shimano 12-speed setup to save coin, or go all in and use SunRace’s own MZ shifter and derailleur, too…

SunRace MZ 12 speed cassette machined lightweight design

At the top of their range is the CSMZX1X cassette, which gets a machined aluminum upper cluster holding the 32/36/42/50 tooth cogs, paired with steel lower cogs. Claimed weight is 439g, putting it just slightly under the actual weight of a SRAM GX Eagle cassette.

SunRace MZ 12 speed cassette machined lightweight design

What’s cool is that you can choose between black chrome or silver lower cogs, and black or gray upper cogs. The design requires a SRAM XD Driver Body on the hub, but actually uses their own adapter to make it work:

SunRace XD driver adapter lets them run a lighter cassette for SRAM Eagle and Shimano 12-speed wide range mountain bike drivetrain groups

The adapter slides over the XD Driver, then the cassette slides on and threads into the XD freehub body just like a SRAM cassette would.

SunRace offers affordable lightweight 12-speed mountain bike groups with 10-52 wide range cassette

Below the top level cassette are a smorgasbord of other 12 speed options, including the MZ91X that gets the largest range of 10-52. Complete option list with specs below:

SunRace offers affordable lightweight 12-speed mountain bike groups with 10-52 wide range cassette

The derailleurs come in two versions, one with an alloy cage and normal pulley wheel…

…and this top end one with carbon cage and minimalist pulleys. Claimed range maxes out at 50-tooth compatibility, though, so you may want to limit the cassette (as if 50 teeth is limiting) to their second largest option.


  1. I believe that SRAM and Shimano 12 speed have different cog spacing, isn’t that so? Therefore I would guess that the cassettes are based on SRAM’s spacing only, given the XD drivers.

    • They used to have different spacing – but as tolerances have gotten tighter and tighter with more and more gears, the spacing is basically the same across brands – on road gear, with the 11’speed cassettes, campy, Shimano and sram are all the same. With 12 the same is true.

      • That’s .1mm of difference, which adds up to over a millimeter of difference in total between the smallest cog and the largest one. Seems like it could be enought to make a difference that affects shifting.

        • I should be able to answer that this week when the first 9100 kits arrive from Germany. My guess is that you’ll get things dialed at the center of the range so that they’re ‘only’ off .5mm at the extremes.

          Sunrace would be wise to split the difference at 3.60, that’d yield good performance with the big guys and best performance with their own parts.

        • Yeah, I think you would probably need to adjust the derailleur for perfect alignment in the middle 2 gears in the range, so that you’d be splitting the misalignment in half between high and low extremes. That assumes that high and low are equally tolerant of slight misalignment. I’d think that would work fine, especially if Shimano is still using a floating upper pulley on their new 12spd stuff.

        • SRAM derailleurs work fine with Shimano cassettes (I ran an Apex1 der with an XTR cassette), and Shimano derailleurs work fine with SRAM cassettes (I ran an XTR derailleur with an X01 cassette). They’ve always worked fine together. We replace Shimano cassettes with SRAM ones all day long on customers’ bikes.

          • You must not like your customers if you’re replacing Shimano cassettes with SRAM. Or it’s part of your business model to keep them coming back twice as often for new cassettes….

            • uhm, what?
              On high end cassette Shimano use multiple titanium cog to reduce weight which reduce durability. Sram keep using steel on all (except some largest cogs on MTB, but not on road) and only save weight by clever construction of the cassette (single piece dome machined from big steel block). The end result is that Sram cassette weight less and full of steel while Shimano weight more and use many of less durable titanium cog.

      • Nope, I have an Eagle cassette on an otherwise full 9100 bike. Not even a hiccup. Except that I received previous gen rotors.

  2. No thanks. 6t spacing for the upper half of the cassette? That’s a big jump between gears and being cross chained 80% of the time means all these 1x drivetrain trains will wear out super fast. Just what the manufacturerstatus want. Expensive non durable parts. As a high milage rider this will not do!

    • Tooth increase Step size.

      With the exception of the 28-34 @21%, those 6t steps on the 10-52t cassette are are all smaller than the 20% 2t jump from 10-12. They’re not super-even, but there are shift ramps to think about and the worst is still smaller than the biggest step in a Force 11-36 road cassette.

      For the nerds:
      10-52: 20% 17% 14% 13% 17% 14% 17% 21% 18% 15% 13%
      10-50: 20% 17% 14% 13% 17% 14% 17% 14% 13% 17% 19%

      • I just thought it was odd that the 10-50 has 4,6,8T steps for the top part of the cassette (for relatively even % steps), whereas the 10-52 does 6,6,6 (with decreasing % steps)

    • Actually I race a Sunrace 11-46t cassette and am winning my age group in the northern Thailand xc series.The Sunrace cassettes are quite durable for me at 67 kilos and I ride about 250-300 kilometers per week. I use a KMC chain and XT rear derailleur and shifter. My current Sunrace cassette has lasted almost a year now and works almost flawlessly. I owned a Sunrace 11-42 before this one and it worked fine. the thing I found to be the case is let the chain break into the cassette for a bout 150 kilometers before you critique it. Mine skipped a bit before the first 100 kilometers or so, but after , I’ve only adjusted it occasionally. The 6 tooth spacing is fine for climbing as I often only have to downshift once when climbing rather than twice with a closer ratio low end. I would recommend them to anyone and that’s for racing as well as general high mileage riding. I would also point out that as the cogs get larger, there NEED to be more teeth between jumps to make a full gear change difference. the very least you should have with 34 teeth or larger cogs is a 4-5 tooth difference and a 34 to 40 and 40 to 46 work well racing for me.

    • 6t spacing works fine for me. I own a Sunrace 11-46 and love the 34-40-46t spacing. No more need to downshift twice to get the right gear. I’m currently winning the northern Thailand xc championship series on on my Sunrace 11-46t x 34t chainring. I’ve had my Sunrace for almost a year and average 250-300 kilometers a week in training. Had ZERO issues with durability. I use a XT rear derailleur and shifter and a goatlink.

    • You can still get Capreo cassettes new, Sunrace also do a bunch of actually quite nice 8 and 9 speed cassettes of their own, including 11-42 wide ratio ones, which are brilliant.

  3. It would be great if the 12 speed spacing for the ‘big three’ turns out to be as cross-compatible as 11 was. Perhaps this website or VeloNews, etc etc could just measure it all, try out the various combinations and let the public know what works/doesn’t work together? Obviously shifters will not work with other brands due to cable pull etc but if the cassettes do that is at least something.
    With SRAM 12 speed road outed (on other sites, not this one) I’m very keenly interested in knowing if these line up with Campy 12 speed as well. No one seems to know what Campy 12 speed cog spacing is.

  4. is there any rational reason for the increasing number of cogs? the constant engineering pressure to add complexity without any viable reasonable advantage is nonsense… the cost alone is just another cash cow for the profits of an inflated and gross business model… add the electronic idiocy for added weight and more fragile crap to bash into useless junk and you’ve come full circle… none of this crap will improve your ride and the shops will gladly sell and install it so you may join the modern set of suckers returning for the next set of improvements, just bring your money… how many of the 10/11/12 cogs do you use? there is no limit on the gullibility of modern fools…

    • I would suggest that you stop buying new products that have been engineered to be superior to previous offerings. Perhaps get yourself some downtube friction shifters and a car with a carburetor. Oh, and quit using the internet. Or a cell phone.

      • The point is that most new products are not engineered to be superior of previous offerings. They are engineered to fill the pockets of people with business degrees running the cycling industry nowdays. Mojoaugogo nailed it.

  5. gives a wider range of ratios and decent hill climbing for a 1x pedelec we don’t all run 2x or 3x where there it is very low, low or high. sounds ideal to me ! the expense, well modern cycles are adorned with some well designed and well tasty bits of engineering quality ain’t never cheap. and this comes from a man with an engineering back ground and not a nerdy modern internet fool who has an opinion. modernity bring it on thanks lads keep up the good work cheers pat.

  6. So they make the larger cogs, the ones that are going to be under tremendous torque as you climb, out of aluminum. And they make the small cogs, the ones that will be under very little torque as you pedal at speed, out of steel. Does that seem completely backwards to anyone else?

    • No, it seems perfectly reasonable. On a 10 tooth cog the chain engages as most 5 teeth. On a 52 tooth cog the chain load is distributed over 26 or more teeth. When you see the Clydesdales with the big thighs charging ahead, they are not slowly drifting anywhere. They are putting large forces on the cranks and thus on the chain. If the 10 tooth cog were aluminum, they would rip its teeth off the first time they used it. Plus the weight penalty of a dinner-plate-size 52 tooth cog would be considerable if it were steel. And it would provide little or no functional or durability advantage over aluminum.

      For the same number of crank revolutions, the 10 tooth cog sees 5.2 times as much chain wear on each tooth as the 52 tooth cog does. So it makes sense to make the little cog of steel and the big cog of aluminum.

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