Do you own a fat bike and wish you could ride it like a true trail bike? The Manitou Mastodon Pro Fat Bike fork offers all-weather performance and enough travel to get seriously rowdy with. In this review, our customer adds one to his Salsa Beargrease Carbon. Check out how it went!
Does a fat bike really need a suspension fork?
There seems to be a lot of passionate people online who say one way or the other. The answer I came to is this: it just depends on what you use that fat bike for. In my case, I want to use it for everything: riding snowy winter trails, sandy beaches, and singletrack. Fat tires cushion a lot of smaller trail chatter, but a moderate travel suspension fork makes it feel like you’re riding a fast marshmallow.
My year-round bike is a custom built 2018 Salsa Beargrease Carbon. The tires are 27.5 x 3.8 Maxxis Minions, and I’ve found that these are an almost perfect size for the activities I do. Big enough to run on groomed snow and some sand (nothing deep), they’re also narrow enough that I don’t suffer too much on the climbs. Downhill is still slower than a plus-bike, but I’m not a speed freak anyway. Plus, I can run over anything in the way, and climb very technical trails without much difficulty (lots and lots of tread and surface contact). But I found that without the fork, I was still bouncing uncomfortably high over roots and rocks, and if I did hit a drop, the shock to my arms could be painful.
I chose the Manitou Mastodon after a lengthy bit of research. When I make a big purchase, I like to plan for every eventuality. Even though the temperature in this part of Idaho won’t get below 20 degrees (F) most years, I wanted a fork that would perform well down to zero. I often take my bike home to Eastern Oregon, where it can drop to 5 or lower, and next year I plan on a trip to Northern Idaho/Canada. Most of the information I found described the Rockshox Bluto as performing poorly without an aftermarket cold-weather seal upgrade, and the Laufs were just too expensive. The Mastodon also allows for the widest of tires (in case I get a wider fat bike) and has thicker stanchions (I’m about 220 pounds). I chose the Pro so that I’d have more adjustability, and the Extended version to fit the 29+ wheelset I plan to build later this year (Note: I’ve found several posts that indicate you don’t need the extended version to fit the 29+, but I chose to go with Manitou’s recommendation).
I ordered the fork and got a good price and fast shipping from Worldwide Cyclery as always. Had my LBS do the install and tested the bike out. A few things to know for this fork. First, it’s specced for a 180mm disc out of the box. Second, the crown-to-axle length for the extended is 531mm, so check your manufacturer’s warranty to see if this presents a problem. Third, if you happen to have a lovely Hope floating disc rotor and Sram Level T brakes, the rotor rivets will very lightly scrape the brake housing. Enough that you get a constant clicking and a tiny bit of rolling resistance. I had to take a Dremel to the brake housing and grind off about a half-millimeter or so. Works perfectly now, but I do need to put some paint back on. I got to test the fork on the local trails in the Boise Foothills; Three Bears one weekend, and Polecat Gulch a few weeks later. Easy to intermediate (I’m still new at this), but the performance was great. No noticeable stiction and the 100mm of travel was more than enough to handle the trails. As I mentioned before, it is very much like riding a marshmallow, with the fork and tires combining to take every bump out of the trail. When climbing, locking out the fork just takes a quick twist of the red adjustment knob. It was a crazy fun couple of rides.
Some of the cons. This is a very heavy fork. You expect a fat fork to be heavy, but it’s about five pounds, one more than the Bluto. Because it can handle a 5-inch tire, it’s about an inch wider than the Bluto. Check your frame clearance carefully before buying. If you think the crown is going to hit the downtube, look at options to prevent damage. The easiest is to get a thicker crown race. Salsa says on its website that the Beargrease cannot take a Mastodon. That is only partially true. Cane Creek just came out with a +6mm crown race that I bought, and it provides about 1mm of clearance on my Medium size frame. They also make a +3mm if you need less. You can also use bumper pads or other fixes, but that can still crack a carbon frame in a crash, so I’d try the races first. If you buy the extended version, it will add 20mm to your front height; I ended up with 26mm because of the race, and my first trip out, I had issues with the front tire coming up on climbs. I dropped the bars about 18mm, and now I have no problems. As far as I can tell, there is no lockout remote available for the Pro version. You can use a MILO for the standard, but the Pro uses the Dorado air spring. I don’t know if Manitou plans to produce one, but I hope so, for convenience sake. You should also be aware that the fork width might make it impossible to fit on some bike racks; I have a Kuat NV 2.0, and the arm of the tire hook just barely clears the fork. It actually rubs a tiny bit when I hit a bump.
Despite those issues, the fork is great, especially if you’re either a heavier rider or ride in the extreme cold (I’m looking at you, you crazy Minnesotans!). The Pro provides lots of adjustability and a better air spring, and you can get it in a 100mm (adjustable down to 80mm) or a 120mm (adjustable to 140mm, though some say 150mm; I’ve only seen 150 on OEMs). Plus, because Manitou knows you might not like the red-and-white stickers, they include a set of grey stealth vinyl stickers to put on (though these lack the “Pro” text). It’s not a quick release, so you’ll need to carry tools, but Manitou’s hex-bolt axle is light and easy to remove and install.