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Mountain Hubs

Shimano HB-MT900-B Front Hub

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 front 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-MT900-B Front Hub weighs in at 158 grams versus the M9100-B version at 137 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.

Many current and new mountain bike framesets feature Boost rear spacing. As such most fork manufacturers also increase the width of the front hub axle in the quest to gain greater strength, wheel stability and wider spaced bearings. The Shimano XHB-MT900-B Front Hub is the non-series Boost 110mm wide axle version of the M9110 front hub. Smooth, fast, sure, durable, and stout,the Shimano HB-MT900-B Front Hub is a stellar example of the full Shimano front disc hub line-up. While the rear version represents a new technology in Micro Spline, with the front Center Lock 15mm E-thru-axle hub Shimano's engineers basically embraced the concept of "if it ain't broke don't fix it". A wise decision as its predecessor already carried the the full array of Shimano's hub strengths.

In the M9100 series parlance, the HB-MT900-B Front Hub is a standard flange hub for j-bend spokes. Offered here in 28 and 32 hole options for the 110mm axle width for a 15mm thru-axle system, this is the so-called Boost variant. Shimano just doesn't add a longer axle, as that is how many competitors do it, but widen the hubs shell so the bearing width is increased ensuring the wider assembly is actually stiffer- as intended. Otherwise why bother? The anodized aluminum shell is built to perfection, and carries the 110mm long oversized aluminum axle that features cone wrench flats for disassembly and adjustment.

Unlike most hub and wheel manufacturers Shimano eschews sealed cartridge bearings, which the engineers feel struggle to manage the angled forces a wheel is regularly forced to endure, creating counter forces that add friction and can limit bearing life. High quality stainless steel ball bearings ride in what Shimano calls a grinded cup and CBN cones. The seals used are a dual Labyrinth and Contact system that is known for incredible effectiveness. Servicing such hub bearings is actually quite simple, but unless you really ride the HB-MT900-B front hub long and hard in terrible conditions, it is actually quite possible you will never service the hub. The bearings, grease, cup and cone, and seals are simply that great. As you can adjust the hub, you control your destiny.

This isn't hyperbole, as our full service shop has barely cracked open a top-level Shimano road or mountain hub for required service over the last decade, and we have sold a great many Shimano hubs and wheels. Our techs are also major fans of the simple spline mount Center Lock rotor system, which makes for fast and easy rotor changes, with ideal accuracy and consistency. Shimano does include an anodized aluminum Center Lock lockring with the hub. The 15mm thru-axle is generally supplied by the frameset or fork manufacturer, not Shimano. If you need reliability, top-level hub performance and plan to build your front wheel up with forgiving and widely available j-bend spokes, keep it simple and pure with the HB-MT900-B Front Hub.


  • Subtle variant of one of the best front mountain bike disc hubs offered, with 110mm axle length
  • For use with j-bend spokes, 15/110mm thru-axle, Center Lock disc rotor
  • Stout machined and anodized aluminum wider hub shell, oversized aluminum axle
  • Features simple an easily serviced cup, cone, and ball bearing design
  • Internals heavily protected by proven Labyrinth and Contact seal system
  • Axle ends feature cone wrench flats for service/adjustment
  • Premium grade materials with direct, simple, and utterly reliable technologies
  • Wheelbuilder specifications
    • Flange diameter: 52.8mm
    • Flange distance: 70.2mm
    • O.L.D.: 110mm
    • Offset: 5.4mm
    • P.C.D.: 44/44 mm
  • Center Lock disc brake rotor interface; Anodized aluminum included
  • Options (TA, hole count): 15/110mm 28 hole, 15/110mm 32 hole
  • Finish: MT900 black
  • Weight: 158 grams