Editor’s Note: This review was written by Mtbr forum member Ben Slabaugh “schlim”. Follow the discussion here.
Specialized Fatboy Review: How I ended up fat
I did not envision myself on a fatbike. After all, I’m a racerboy – I’m into saving grams where possible, preferably from my wheelset. It’s rotating weight, right? Easier to pedal is better. Butyl tubes, tubeless, supersonic sidewalls, low rolling resistance are all entrenched in my vocabulary. A test ride changed my mind.
I happened to jump on a Fatback at Outerbike in Moab. You can read my review of that bike, but it was an immediate attention grabber for me. Krob and the DL were off riding, well, normal bikes and I grabbed the Faback 190 while waiting for Yeti’s bling carbon Arc 29er to be returned. There was no snow there in the desert, and the Fatback just looked massively weird. Except it wasn’t. It was amazing.
Fatback 190 tested in Moab was one of the reviewer’s candidates. Photo courtesy of Ben Slabaugh/schlim.
I got home and told my wife, “I think I’m going to need a fatbike.” She was not surprised. She’s a very understanding woman. Given the Fatback experience, I narrowed down the neighborhood by looking for a 190mm rear hub spacing, 100mm bottom bracket, clearance for the widest tires on the market, a carbon fork, and somewhat affordable total package.
Up for consideration were the Fatback 190 (obviously given my demo), the 9:zero:7 190, Salsa Beargrease carbon, Surly Moonlander, and the Specialized Fatboy. Briefly, the aluminum Fatback, while USA made, was expensive for what you got (same price as a carbon Beargrease). The Beargrease is carbon, pretty, and light, but designed around 170mm rear hub spacing, which limits what tires and rims it can handle. The 9:zero:7 and its diamond section curving toptube somehow didn’t do it for me asthetically, plus I would have needed an aftermarket carbon fork. The Moonlander is steel, which is generally suggests a nice ride, but the weight concerned me. The complete bike also had some uninspired components. It’s a small quibble, but the Borealis Yampa didn’t make my list because the complete bike ships with 3.8 tires (and only 27tpi on some builds). However, it certainly deserves a hard look if the full carbon frame option is important to you.
I settled on the Specialized Fatboy. It had the 190 rear hub, massive 4.6” tires I wanted, carbon fork, plus a decently light aluminum frame, grip shift (which I like very much), 2×10 gearing for range and cheaper maintenance (I’m opposed to SRAM’s $400 11-speed cassettes, a wear component, on principle), Shimano hydraulic brakes (I will tolerate no other brand’s current offerings), and more aggressive geometry borrowed from the Carve/Crave. Additionally, my race team is sponsored by Specialized, significantly increasing my chances of even getting my hands on one this season.
Geometry and fit
It’s always a dangerous proposition to deposit money on a bike you have not ridden. It’s redoubled when virtually no one else has either. What made me more comfortable with the idea was that the ETT measures 625mm, which is the same as my Yeti ASR-5. I’m running a 75mm 6 deg stem on the Yeti and the Faboy ships with a 70mm 6deg stem.
Some folks have said the toptube feels short. It isn’t. I measure the center of the headtube at the headset horizontally to the center of the seatpost as exactly the same on both the large (long, low, and relatively slack) ASR-5 and the 19” large Fatboy. I do think that with the shorter stem, the short stack height of the headtube and the flat bar, it kind of tucks everything in somewhat, resulting the compact feel. Compared to a large Trek Farley with a 100mm stem, the Specialized Fatboy feels much less stretched out, slightly tighter, and better balanced. At 6’1” with ape arms and a 34” inseam, a medium would have been a crunch and I probably would have had issues with seatpost extension. The medium Borealis Yampa I took a spin on had lots of headset spacers and a riser bar building up the stack height, so I can’t really comment on Spec fit compared to that one.
The bottom line is that the Fatboy is purpose built to run aggressively, but neutral with its low stack height and shorter stem. I did swap in a 20mm rise Easton Haven bar to match what I’ve got on my Yeti and further dial in the feel. The stock aluminum “mini-rise” bar was far too unyielding for my comfort and I needed slight lift to take some pressure off my palms.
The wheelbase feels respectably tight, but given my lack of experience on fatbikes, I can’t really comment on the merits of a shorter chainstay in the snow compared to a longer 9:zero:7 or a Yampa. What I can say is that when climbing dry ground, the rear wheel felt nicely tucked underneath me to facilitate good climbing and a responsive feel descending. I can lean back and lift the front wheel back into a different line if necessary.
Unfortunately, the chainstays flare quite wide and I have knocked my heel against them a lot. To keep paint on the bike, polyurethane helicopter tape and a neoprene sleeve on the drive side are indispensable. The tradeoff for the wide chainstays are the gloriously massive 4.6 Ground Controls mounted in 90mm rims. In person, they look spectacular and intimidating. Additionally, I’m betting the future standard will be 190, and that additional wheelset options in that format will materialize as time goes on.
What I added/altered
I already mentioned the switch to the Haven bar for some additional hand height. While the glossy black Henge saddle looks trick on the Fatboy, it didn’t agree with my backside the first few rides out. I may eventually give it a chance to break in, but I went back to my trusty WTB Pure V that I know is a winner. As a survivor of multiple 24 hour races, it’s well adapted to my rear. Additionally, I swapped out the low-end Specialized post first for a Thomson Elite, and then for an Easton EC70 carbon post. The carbon fork, bar, and post combined with the high volume fat tires effectively cancel out the overly harsh ride qualities offered by aluminum frames.
After doing the math on the weight of gorilla tape and Stan’s vs. lighter tubes, I settled on the Specialized 24 x 2.4-3.0” tubes. They weighed in at right around 235g apiece and filled out nice and evenly. Over the 610g stock tubes, I dropped 285g per wheel. I might try the tubeless route eventually, but the bead is very loose on the Ground Controls. I’m betting on reliability for now vs. potentially rolling off a tire in frigid conditions and having to deal with sealant everywhere. I also tossed on some red Wellgo MG-1s and a red bottle cage to match the frame. Weighed without my Dave’s Mudshovel fenders or GPS, she’s rolling at 29.7 lbs.
So what’s the ride like?
The Fatboy definitely feels like it leans to the fast side of the spectrum vs. plodding, which is saying something given the massive width of the rolling stock. It can certainly grind along just fine, but when standing up and hammering, it will move. It’s light steering even brings out a zippy feeling on a slight decline. The geometry facilitates this, as it puts a little more weight up front and mimics that of a 29er hardtail. The comparatively low gearing of the 22×36 combined with the 11-36 cassette is absolutely necessary in deep snow and sloppy conditions. Stomping on the pedals with too much torque to the ground causes the rear wheel to dig in and slide out sideways in unpacked snow. Regulated power and spinning is critical to keeping momentum.
In dry stuff, the optimal pressure seems to be around 8psi or so. It’s difficult to tell since my floor pump isn’t particularly accurate at low pressure, and my analog dial gauge broke after the first few days of usage. Anything less in the front, though, and the bike risks some self-steer on dry trails. The bouncing also becomes more pronounced and the ride (oddly) harsher. I learned this the hard way on a night ride using the headlights when the bike had so much traction that it steered me into a hole I didn’t see and then bucked me off. That was a-typical though. The planted feeling from the bike and confidence letting it roll through anything is just tremendous, especially around built-up corners.
In snow, which was the whole point of the bike for me, I generally run the tires so I can push them in about a third of the way in toward the rim. The pressure is around 5-6 PSI I believe, and I’ve run them even lower. I can see that the Ground Control tires are developing 3-4mm diagonal wrinkles in the sidewalls due to low pressure rides. In general, I can out-climb someone in soft snow who is running a Larry or a Nate tire. Those on Buds and Lous seems to have less difficulty and I’m working to hang with them. It’s clear that the additional volume is an advantage. There does reach a point, though, where too low of a pressure results in the rear struggling to find grip in powder. It’s almost as if the floatation overcomes the ability to dig in and get traction. It’s a very odd thing, but absolutely real in deeper conditions. On one steep climb in nearly unbroken powder around 3-4 inches deep, it was the difference between being able to ride some of it vs. walking all of it when I aired down to a very low pressure. It was a useful lesson in terms of the Fatboy’s behavior and ability. Downhill sections in snow sometimes result in a pretty significant drift (especially when the front wheel is turned and the bike is heading straight). Happily, on one descent in deep, snowmobile churned snow, my bike stayed upright and other fatties with narrower tires (3.8-4.0) did not.
On packed courses that are groomed or stomped down by snowshoes and snowmobiles, the Fatboy just flies. For me, it feels most comfortable and capable in these conditions. Getting into the 36t ring allows the bike to carry so much momentum that it usually evokes a happy whoop from me. The grip shift is definitely helpful, as it allows a single click front shift and easy rear shifts when paired with thick down gloves. Rather than my usual clipless setups, I’ve been using the Wellgo MG-1s I mentioned earlier, which are optimal for quick exits, outriggers, and for standing starts uphill in the snow. I don’t have to worry about snowballs building up in the mechanism, and my Five-Tens paired with alpaca socks keep my toes nicely warm and comfortable. With the stealth rubber soles, climbing is no problem.
The Fatboy has carried me along just fine down to 10 or 12 degrees with no malfunctions, however I found out quickly that ice is death. Given our strange winter, we’ve had some pretty large ice patches in some places instead of the usual snow. On these, the Fatboy and Ground Controls don’t offer much advantage or assurance. My major mistake seems to be seeing the ice patch approaching and feathering the brakes. This unfortunate maneuver causes me significant bruising and abrasions, such that I ride with soft elbow and knee protection now. The bike has been mostly unscathed. For next year, I’m weighing the pros and cons of adding in Grip Studs to the Ground Controls or alternatively picking up some studded Dillingers to keep from losing the front end in suboptimal conditions and the yardsales that result. Ouch.
What would I change?
Much of what follows is nitpicking, but I hope Specialized takes it into account for future updates to the Fatboy. First, the top tube could be lower or bent for sudden dismounts. While I have managed not to rack myself, I have come uncomfortably close in sudden stops and deep snow. Fatback and 9:zero:7 have the right idea here. The straight tube is nice to look at, but function over form should rule for extreme conditions.
In the same vein, because the top tube is so tall and the stackheight is so short, with the stock bars the brake levers do impact the top tube. I solved this with the Easton riser bar, but folks who run the stock setup may find themselves with dented and scarred top tubes. Mine is covered with helicopter tape for a little additional insurance when my lights and batteries are mounted to the bar.
The previous-generation Deore brakes seem pretty good, although the rear has developed some pump-up resulting in little movement in the lever to full bite in the cold. This might be solvable by bleeding out some of the mineral oil, but I haven’t been bothered enough to mess with it yet. Additionally, the brakes do squeal in moisture, unlike my XTs and XTRs. It goes away once the rotors heat back up. I’m thinking about maybe trying an organic compound or sintered pads to see if that improves things.
While I would not trade out the grip shift and am pleased with the new 2×10 redesign on bearings, the stock interlocking grips aren’t comfortable. They taper down to the end of the bar, where there is little rubber compound left to absorb shock from a rigid front-end. I’ve swapped them out for trimmed ESI Chunky grips, and that seems to be a huge improvement so far. I may try shortie Ergon GP1 grips at some point as well to compare.
Taking a look at the frame, I was curious whether it could handle a 29+ setup. The stock wheelset with the Ground Controls is 740mm in diameter. A 29+ with 3.0 Knards is 780mm on Rabbit Hole rims according to Surly. Measuring, the frame clears the extra 20mm radius, but it would impact the SRAM X.7 top pull front derailleur. Unless a lower profile front derailleur is available (maybe a direct mount XTR would work?), 29+ on the Fatboy would require a single ring setup.
It would have added some weight, but I would have preferred a through-axle setup for precision, ease of removing the front wheel, and consistency with modern design. Quick release, outside of road applications, feels like outdated technology and comes across as flimsy on a fatbike. Would TA provide any kind of performance advantage? Who knows. However, any kind of increased resistance to torsion should be beneficial. Specialized is still in love with QR and it’s inexplicable.
Lastly, what a crummy rear cassette! A 348 gram Sunrace? Really? I’ll run it until it’s shredded, but then an XT is going on. By the way, I can get 5 new XT cassettes for the price an X01 XG-1195. 2×10 just makes more economic sense to me right now, but I might change my mind if the front derailleur gets packed with ice and fails me.
Having owned the bike for six weeks, I remain convinced I picked the right one. Nitpicking aside, the Fatboy is a tremendous value and a well-designed first generation product. I have never been able to ride outside any day I felt like in January and February before. Fatbiking (in my short experience) is about fun, adventure, determination, accomplishment, and a little bit of insanity. Specialized has rolled all of this up into a nice package that makes me (of all bizarre things) actually want to go out in 12 degree temperatures to ride in the snow. In the dark. With headlights. That’s not just the bike making me a better rider. It’s life altering.