Just In – Manitou Magnum 27.5+ and 29+ Fork

by Brian Mullin on August 19, 2015

Manitou Magnum fork

The travel throughout its stroke is supple and smooth, with low stiction and drag, and its plush ride offers great support and control. The fork offers excellent small bump and superb medium bump compliance with a high degree of plushness, and it ramps up in stiffness for big hits and larger stuff.

The Manitou Magnum is a purpose built Plus specific suspension and comes in 27.5+ and 29+ sized configurations and can fit up to 3.4″ wide tires. The forks have a 35mm chassis, a hollow crown, their strong reverse arch design and have an 110 x 15 axle spacing utilizing their QR15 Hexlock. The 27.5+ has a 48mm offset and comes in 80-140mm of travel while the 29+ has 51mm offset and 80-120mm of travel. Also, the Plus fork was given ride heights that retain the bikes proper geometry, so they have a shorter than usual axle-to-crown height. The forks retail for $900 and are available now.

Although fat tires offer comfort, traction and control on less than ideal terrain, their size and weight cause kinetic energy issues during initial stroke and bigger bumps, exacerbated by the muted impacts due to low tire pressures. They optimized the Magnum fork for the Plus tires and their increased unsprung weight and it offered compliance for everything from small bumps to big hits. During the initial stroke, it lets the tire easily move without overcompressing.  On bigger bumps, the fat wheels mass creates a greater kinetic energy and causes an overstroke and this builds up unnecessary spring energy, and this in turn is pushed into the rider followed by the corresponding high rebound velocity. The Magnum was designed to get the right balance between initial stroke movement and high-velocity control.


Manitou Magnum fork - features   

Features

    • Spring
      • Dorado Air – single input to charge positive and negative air chambers for perfect spring balance providing unmatched small bump compliance.
      • DOS – Dynamic Over Stroke: eliminates dwell at top out and provides a seamless transition from extension to compression resulting in a smoother stroke.
      • IVA – Incremental Volume Adjust: Allows the rider to simply customize the air volume based on riding style or terrain
    • Damping
      • MC² -Multi Control Compression: Platform, High and low-speed adjust.
      • IPA – Incremental Platform Adjust: Used to dial in the perfect amount of pedaling platform.
      • TPC – Twin Piston Chamber: rebound damping, custom tuned for plus sized rolling stock
      • HBO – Hydraulic Bottom Out: Externally adjustable, derived from the award winning Dorado to provide a bottomless feel

Manitou Magnum fork - on bike front view

27.5+ Testing

My local trail conditions in the Colorado Springs area consist of rocky terrain along with sand and vast amounts of loose gravel. The Pikes Peak granite weathers and decomposes into pea sized gravel and sometimes creates deep blankets of loose gravel covering slopes and trails. It produces some of the most humbling trail conditions and can cause tire washouts and traction and braking loss at inopportune moments. Fat tires with meaty and tall tread patterns tend to shine in the gravel and sand since the larger volume tires give better float and bite and produce larger footprint into the terrain. The new 27.5+ and 29+ tires on the market seem like an ideal candidate for dealing with this dreaded gravel and any loose conditions, including snow, rocks, loam, dirt, sand, and mud.

For my initial testing in the Plus world, I decided to start with 27.5+ tires and mount them on a 45mm rim and a Boost front hub and install everything on a 27.5+ fork. I ended up choosing a Manitou Magnum Pro 27.5+ fork with 140mm of travel. For wheels, I used the Panaracer FatbNimble 27.5×3.5 tire on a WTB Scrapper i45 rim mounted to an Industry Nine Boost hub, which were built up by Chris Murray Wheel Works. I wanted to use 27.5+ tires in the rear of my Ibis Ripley, but the rear spacing barely allowed a 2.3 tire, so I ended up using WTB Vigilante 29×2.3. Even the Vigilante required me to get the tire seated perfectly on the wheel and at low pressure else they would rub on the right-hand seatstay. I’ll be installing the Magnum on my Ibis HD3 27.5″ bike next for a thorough test on a different bike platform.

27.5+ Test Set Up

  • Bike: Ibis Ripley 29er
  • Fork: Manitou Magnum 27.5 fork with 140mm of travel
  • Front Wheel: Industry Nine Boost hub (110×15) and WTB Scrapper 27.5 i45 rim (measured 45 inner & 49 outer)
  • Front Tire: Panaracer FatbNimble 27.5×3.5 (measured 28 9/16″ tall & 2.9″ wide carcass)
  • Rear wheel: DT Swiss XM 1501
  • Rear tire: WTB Vigilante 29×2.3 (measured 29 7/16″ tall & knob width 2.34″ & 2.28″ wide carcass)

Manitou Magnum fork - hexlock axle

First Impressions

I have been using the Manitou Magnum for close to two months now on my Ibis Ripley. I am highly impressed by the ride quality, adjustability, and especially their MC² (Multi Control Compression) cartridge damper. I have taken the fork into all sort of conditions, from mellow x-country to technical terrain, and I have been amazed at how it has shone and was rarely fazed by much of anything. The travel throughout its stroke is supple and smooth, with low stiction and drag, and its plush ride offers great support and control. The fork offers excellent small bump and superb medium bump compliance with a high degree of plushness. It ramps up in stiffness for big hits and larger stuff, though I haven’t slammed into the bottom out bumpers much. The fork does an excellent job of taming any of the usual bouncy and pogoing effects from the heavy and large low pressure Plus sized tires, especially in rock gardens and chunder. You still need to deal with how the fat tires react, as they can still be a handful, but the Magnum’s custom tuned suspension drastically reduces it. On rare occasions, I found that the fork could pack up slightly and get a bit squirrelly though the big tires kept powering along anyway. The 35mm-diameter tapered aluminum stanchions and their reverse arch, and hollow crown offer great stiffness, though with such monstrous sized tires and their low pressures its tough to get an exact quantitative precision on things. At first glance, the front HexLoc 15QR axle seems odd, but after using it a couple of times the Hexloc is functional and easy to install. I haven’t had any loosening issues, and the axle provides more than enough tightness for the wheel and fork interface.

Measured Magnum Weight: 2071 grams

Manitou Magnum fork - adjusments

Adjustments

I haven’t found the need to play with the air pressure much once I set it for my weight and desired sag. I left the silver knob HBO (Hydraulic Bottom Out) at its maximum default (6 positions) until I get more airtime on bigger jumps, then I’ll alter it to get the proper bottom-out. The MC² cartridge damper allows for both high and low-speed adjustments. I set the middle black high-speed dial to one notch less than its highest setting (6 positions) which offered a stable and firm platform when low-speed is closed up. The most useful feature was the red levered low-speed adjuster, and I moved it all over the place depending on what I was riding. I opened it up fully for descents and used it in the middle for climbing and closed it down to its maximum for fire roads. It had a nice notch throughout its four indented movement and was easy to adjust on the fly. I haven’t yet played with their IVA (Incremental Volume Adjust) over on the Dorado air chamber that allows you to adjust the air volume by moving around air spacers on the upper stack. I ran the ten position rebound faster than the default for a better return during aggressive riding.

Manitou Magnum fork - on Ibis Ripley

Conclusions

The Manitou Magnum Pro offers a great ride, that is plush, composed, smooth and supple, with support and control. It’s purpose built Plus tire design and technology help tame any bounciness and pogoing effects from the big low pressure Plus sized tires. The multitude of adjustments, including the Dorado air spring, rebound, high and low-speed of the MC² cartridge damper, Incremental Volume Adjust and Hydraulic Bottom Out are highly useful and functional.

{ 2 comments… read them below or add one }

sot April 28, 2016 at 11:25 am

I know it’s been awhile since you reviewed this fork. Do you know if the 27.5 fork will allow a 29+ tire to clear the arch? What is the measurement of the center of the axle to the lower edge of the arch?

Thanks,

Reply

Brian Mullin April 29, 2016 at 4:15 pm

I’ll measure it when I have a chance, but I very much doubt it. The 27.5+ is also a standard 29er fork with a Boost axle spacing. I would assume it would fit up to a 29×2.4 but not much else.

Reply

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