Manitou Magnum 27.5+ and 29+ Fork
Manitou says that their new Magnum fork has been designed from the ground up to work with 27.5+ and 29+ tires, and that includes an entirely new chassis, custom valved damping, and an air spring system that's been lifted from the Dorado downhill fork and tuned for this application - more on all the fork's tech below. Travel ranges between 80 to 140mm for the 27.5+ model, and 80 to 120mm for the 29+ fork, and there's enough clearance for riders to fit a massive 3.4'' wide tire. The Magnum is already shipping to bike shops, and it retails for $900 USD.
Manitou was at pains to make it clear that the Magnum is not just a 29er fork that's been widened out and spec'd with a 15 x 110mm axle, and that the purpose-built fork is actually 5 - 7mm lower from axle-to-crown than its competition for this very reason. It also sports the company's reverse arch design, a machined out hollow crown, and the 15mm x 110mm thru-axle is Manitou's own Hex Lock design.
The fork employs a very similar air spring as you'd find inside the Mattoc and Dorado, with the air valve at the bottom of the leg pressurizing both the positive and negative chambers simultaneously and to nearly the same pressure. This near-balancing between the positive and negative air springs is said to make for a responsive top end to the travel, and Manitou says that the fork's active early stroke is important as it takes away the high-volume front tire's tendency to act as an undamped air spring. In other words, less uncontrolled bounce that first time fat bikers often take notice of, and also more control.
One of my few complaints with the Mattoc
was its lack of volume adjustment, and while the fork's Hydraulic Bottom Out control helped in this regard, the ability to tune mid-stroke and bottom-out by changing the volume of the air spring is handy. Manitou listened and has come up with something they call Incremental Volume Adjust, a nifty tuning system that allows the volume of the air chamber to be changed by moving 10mm spacers above or below the air piston itself, a process that only requires releasing the fork's air pressure and opening up the top cap. There are four positions available, and the neat part is that all of the pieces are contained within the fork - there's no spacers floating around in the bottom of your tool box.
It works like this: release the fork's air pressure and then unscrew the top cap - the IVA assembly is attached to it and will come out with it. The plastic spacers that determine the height of the air piston can be pushed off of the rod by hand, allowing you to reposition the piston for more or less progression (higher for less, lower for more
) and then reinstall the spacers accordingly. It shouldn't take more than a few minutes to make changes.
The Magnum's damper employs all of the company's high-end, acronym-heavy damper technology that's laid out in their TPC system. TPC means 'Twin Piston Chamber', and it's exactly as it sounds: there's a rebound piston at the bottom and a compression piston at the top. The fork's MC² compression unit allows for both high- and low-speed adjustment, and the Hydraulic Bottom Out control dial at the center allows riders to tune how the fork ramps up in the last 25mm of its stroke. As its name suggests, HBO harnesses oil displacement to slow the fork down during compression in the later stages of its stroke, doing so by using a position sensitive valve on the bottom of the MC² compression damper. As the fork nears the end of its travel, a small extension on the end of the Magnum's rebound damper enters the hollow HBO unit, and since the confines are tight and the entire system is submersed in oil, the fork's compression action is slowed.
The Magnum is coming stock on the front of Trek's new Stache hardtail that we just reviewed
, as well as Rocky Mountain's recently released Sherpa adventure-mobile
.Be sure to check out all of our Sea Otter Classic images in this gallery.