Shimano FH-MT901 Boost Micro-Spline rear hub - 264g, 100 POE- Mtbr.com
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  1. #1
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    Shimano FH-MT901 Boost Micro-Spline rear hub - 264g, 100 POE

    Just got my hands on the new Shimano FH-MT901-B rear hub...

    Counted the POE and it's ~100 clicks! (The clicks are tight enough that it's actually kinda hard to get an accurate count.) Whoa. Light as well @ 264g with the Center Lock rotor lock ring. What I don't understand is that Shimano says it has 7 degree engagment (51POE)... but I count almost twice as many clicks when turning the freehub by hand?

    Apparently this is the non-series XTR rear hub. Meaning Shimano builds it with XTR internals in a black XT hub shell (doesn't have the low disc side flange of the XTR rear hub). So it's a few grams heavier than XTR, but less expensive.

    Shimano released several non-series components with the XTR M9100 line-up. These MT900 series options are considered XTR quality and have all the same features and materials, but as in the case of this Boost spacing rear hub, less machining has been done on the hub shell, and a black finish has been used, with the end result being the Shimano HB-MT901-B Rear Hub weighs in at 258 grams versus the M9100-B version at 237 grams. And it doesn' say XTR. That's all, and you save some money in the tradeoff for grams and a loss of logo, albeit the most prestigious tag in mountain biking.

    The big news with the release of Shimano's 12-speed XTR M9100 series groupset is a major change in the rear freehub design. The move from the standard Hyperglide (HG) freehub that has been a Shimano feature for years, to the Micro Spline design was crucial for the engineers to develop an efficient, reliable, and long wearing freehub that could support the requirements of a 10T small cog with 11 others on the same design. Some of the space requirements were solved through the concave rear Beam Spider of the M9100 cassette, which is why the Micro Spline freehub is shorter than you'd expect. As usual with Shimano, total integration of engineering, materials and technology allowed for a true XTR-level, world class rear hub design for 12-speed mountain use. While Micro Spline has made this all come together, it is hardly the only technology or feature used in the Boost frame-ready FH-MT901-B Rear Hub.
    Last edited by 06HokieMTB; 2 Weeks Ago at 08:48 AM.
    I like 'em long, low, slack and playful

  2. #2
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    Cool! Looks very well built, and price seems good too.

    But no 6-bolt version???

  3. #3
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    Can you take it apart and snap some photos of the mechanism?

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    Quote Originally Posted by Schulze View Post
    Can you take it apart and snap some photos of the mechanism?
    Shimano doesn't want it opened up, it is listed as an assembly and not to be disassembled in the dealer manual.

    I just got my hands on an XT wheelset today, spinning the wheel while holding the freehub is odd. Sometimes it will go completely silent and just spin away, other times it clicks quite distinctly. It will be interesting to see what it does on the trail. I'm going to use these wheels on a new Ripley build for a little while, until Onyx gets their MicroSpline conversion for the classic hubs out. Then they will end up on a different bike. The way they spin silently is exactly what I expected from the Scylence hubs, the mechanism is supposedly very similar to what Scylence was supposed to be. Maybe they just retuned the springs inside to make engagement more reliable and the Scylence capability is still in there, just not consistently enough to make the claim?

  5. #5
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    So it's quiet. But not. But still kinda is?
    I like 'em long, low, slack and playful

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    ok now I want to buy one just to bust it open.

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    Quote Originally Posted by 06HokieMTB View Post
    So it's quiet. But not. But still kinda is?
    It's quiet except when it's noisy. Nothing kinda about it, it's all or nothing. The question is how it works on the dirt, hopefully I'll get a chance to find out this weekend. I'm a big fan of quiet. But the more I play with it on the stand, the less often it is quiet.

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    I just finished building a set of wheels with the shimano HB-MT900-bs and HB-901-bs hubs (straight pull 28H). I had always wanted to build a set of wheels and was motivated by the price of these hubs. The hubs were 58 for the front and 137 for the rear hub.

    The target use of the wheelset is durable XC (or light all mountain). The build consisted of Light Bicycle RM29C19 carbon rims and Sapim CX-Ray spokes. I called Shimano technical support and they sent me the wheel building document for the hubs. The document did not work well for calculating the spoke lengths. The dimensions and recommended way to calculate lengths resulted in spokes 2mm too long.

    The end result was 720g front, 770g rear (without rim tape)

    The freehub noise sounds like a fishing reel. Very high pitched and frequency. I prefer the sound of a DT240s hub by far.

    Light Bicycle recommended a maximum spoke tension for their rims. The recommendation did not correlate with a set of wheels that I had them build (both sets are symmetrical). I built with spoke tensions similar to the set that Light Bicycle built. Measured with Park Tool spoke meter. Rear 163/107kgf, front 163/131kgf.

    shimano_hub_dimensions_for_wheelbuilders_v2.pdf

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    Lb says 180 kg max and the park tm1 reads low so in reality your rear is 140/90.

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    Quote Originally Posted by dcriffraff View Post
    The freehub noise sounds like a fishing reel. Very high pitched and frequency. I prefer the sound of a DT240s hub by far.
    dcriffraff, are you experiencing similar with the freehub sound as Velodonata?

    Quote Originally Posted by Velodonata View Post
    spinning the wheel while holding the freehub is odd. Sometimes it will go completely silent and just spin away, other times it clicks quite distinctly.
    I like 'em long, low, slack and playful

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    Quote Originally Posted by Velodonata View Post
    It's quiet except when it's noisy. Nothing kinda about it, it's all or nothing. The question is how it works on the dirt, hopefully I'll get a chance to find out this weekend. I'm a big fan of quiet. But the more I play with it on the stand, the less often it is quiet.
    Wonder if that's just the freehub internals grease bedding in?
    I like 'em long, low, slack and playful

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    I don't want to sound like "I know it all" but, the information on the Light Bicycle website and the information sent with the rims indicate 120-130kgf front wheel non-drive side/rear wheel drive side. I am not saying that your information is wrong, just different from what is on their website and the document they sent with the rims. The wheel they built had high rear spoke tension about what you claim to be the max. Additionally, a blanket statement regarding the park tm1 is certainly not true since you can calibrate the gauge. I have never calibrated it and I don't know how my gauge reads relative to actual kgf values so you may (or may not) be correct with your assertions.

    My hub always makes noise. It never is noise-less. I will say that I did not play around with it much. I don't notice it go silent when I ride. I wonder if the Shimano fishing reels have the same type of mechanism

    Shimano FH-MT901 Boost Micro-Spline rear hub - 264g, 100 POE-109.jpg

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    It has been maybe a year since I looked at their site, I apologize. It seems odd they'd spec tension so low since all their rims used to be 180kgf. I've calibrated my TM-1 and three others. They've all been accurate up to 100kgf then start to deviate. At 130 they showed about one number higher than my load cell indicated.

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    Quote Originally Posted by 06HokieMTB View Post
    Wonder if that's just the freehub internals grease bedding in?
    Yeah, could be. It's likely some sort of breaking in process, but it's also unlike any other hub I have ever played with. I'm not sure if it's a good thing or a bad thing, hubs are usually very consistent in their actions at least up until they break. It's not that similar, but this hub makes me think of the old American Classic cam plate freehubs, I guess just because it's also funky and has unique characteristics. You can't meaningfully say much about a hub without riding it, but it looks nice and spins well. It's just got such an erratic sound and occasional lack thereof that I'm really curious how well it will perform.

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    Quote Originally Posted by Velodonata View Post
    I just got my hands on an XT wheelset today, spinning the wheel while holding the freehub is odd. Sometimes it will go completely silent and just spin away, other times it clicks quite distinctly. It will be interesting to see what it does on the trail.
    Like this?

    I like 'em long, low, slack and playful

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    Quote Originally Posted by 06HokieMTB View Post
    Like this?

    Yes, something like that.

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    Sounds like this normal

    The rear hub was initially a disappointment after becoming enamoured with the now discontinued "Scylence" free hub I rode in Crested Butte, but things have changed. Nick Murdick, Shimano's MTB product manager, told me that in his experience the regular free hub starts off singing when first freewheeling and then becomes very quiet after a few seconds. Early on my rear hub didn't seem to stifle itself but now it that it's broken in the whine ends, and it happens very quickly indeed. It's not totally silent in my workshop but it's quiet enough to seem silent on the trail.
    https://nsmb.com/articles/150-days-s...eone-e13-yeti/
    I like 'em long, low, slack and playful

  18. #18
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    Quote Originally Posted by 06HokieMTB View Post
    I still only have it on the stand, but the drivetrain is ready to go, just finishing up some fork work. I am now even more curious to ride it. From setting up the drivetrain it seems that the faster it's spinning the more likely it is to be quiet. And it spins every bit as silent as my Onyx hubs when it drops into quiet mode. Basically like that video but I think mine runs silent a little longer in a coast down, then there are the little blips of noise, then it eventually goes into that full on ratchet mode. My hope is that it remains quiet during most significant coasting on a typical ride, I'm fully addicted to silent hubs at this point after a few years on Onyx. These aren't going to be my primary hubs for long, even with the weight penalty I expect to prefer my Onyx wheelset for the 100% silence and the overall sublimely solid smoothness. But this XT wheelset might just be a nice setup on a bike that doesn't get ridden as much for a significantly smaller investment than another set of Onyx hubs.

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    I'd go crazy with this silent/noisy thing.

  20. #20
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    I finally got a real ride in on the XT version of the Scylence/Not Scylence hub. It's definitely not silent, but it is pretty quiet. It was my first ride on a completely new bike so the hubs were not my primary point of attention, and to their credit they did nothing to bring themselves to my attention either. I almost forgot that I had been curious about how they would perform. The weird on again, off again ratchet noise was there but not that noticeable due to the overall low noise level. They are not going to replace my Onyx hubs as first choice, but they will do just fine as a backup set or to go on a future hardtail as long as they are also reliable.

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