The best fat bikes are cartoon-looking mountain bikes with huge tractor type balloon tyres. If you fancy one, here's what you need to know.
Imagine a mountain bike coming to life off a cartoonist’s drawing board. Well that’s a fat bike. Massive balloon tyres deliver gobs of grip and a sasquatch-size footprint in the dirt. The large air volume in the tyres also makes them surprisingly comfortable, even without suspension, and that means the frames can be simpler with less to go wrong. Once you’ve tried fat, there’s no going back, or so they say.
The general tyre width window on fat bikes is 4in to 5in. Typically and historically speaking, the rim size is usually 26in. But there are now 27.5in rim fat bikes coming out. And, as ever with fat bikes, there are folk who have gone OTT and made 29in fat bikes. It’s arguably best to ignore rim size for now. Tyre width is far more important with fat bikes.
Anything much narrower than 4in and you’re dealing with a Plus bike. If you’ve already tried the best mountain bike models in the traditional scene, a fat bike may just tick the boxes you’re more interested in.
Trek Farley 5
Big name peace of mind and support
Wheel size: 27.5in | Frame sizes: S, M, L, XL | Weight: 14.66kg | Frame material: Alpha Platinum aluminium
Pros: Carbon fork, good size range, dealer network and back-up
Cons: Only 10-speed Shimano Deore with narrow cassette range
Trek might not be a specialist fat bike brand, but with its headquarters in Wisconsin, USA, it’s no stranger to harsh winters and frozen trails. As such the Farley 5 is probably the most-sought after staff bike at Trek during the off-season. It gets a high-quality Alpha Platinum alloy frame with OCLV carbon fork and comes stock with 27.5in wheels and 4.5in tyres (Trek’s own Bontrager Gnarwhal). Sliding dropouts at the back and sufficient clearance at the front means that you can also run 26×4.7in wheels and tyres if you wish. Trek supplies the Farley 5 with a dropper post, making it more fun on challenging trails, and the fork is long enough that you can swap it for a suspension fork at a later date without messing up the geometry.
Ignore the name: This bike will make you smile
Wheel size: 26in | Frame sizes: XS, S, M, L, XL | Weight: N/A | Frame material: 4130 cro-mo
Reasons to buy: Traditional steel frame should last a lifetime. Great size range.
Reasons to avoid: Mechanical disc brakes.
Surly has been at the forefront of singlespeed and fat bike design for donkey’s years, and enjoys a loyal customer base. The Wednesday uses a traditional 4130 cro-mo frame for ultimate backcountry repairability. It’s bristling with rack mounts and bottle mounts, so you can head off into the back of beyond with all the essentials. Adjustable dropouts let you run either 3.8in or 4.6in tyres. Hey, you can even go mad and run 29x3in wheels for a more traditional ride.
Wheel size: 26in | Frame sizes: S, M, L, XL | Weight: N/A | Frame material: 6061 aluminium double-butted
Pros: Big 4.8in tyres for a full-fat experience. Wide range 11-speed drivetrain.
Cons: Tall seat tube.
Kona has never shied away from making niche bikes, hence its two-model fat bike line-up. £500 less than the Woo, the Wo still gets a double-butted alloy frame and alloy fork along with the capability to load it up with gear and head out into the wilderness. The Wo has an excellent wide-range drivetrain – important if you’re fully loaded, or riding on soft sand or snow – and comes with dependable Shimano brakes. With massive 4.8in tyres on 26in rims, it offers the full-fat riding experience, and an ideal set-up for the most challenging of conditions.
Canyon Dude CF7
Adjustable carbon beauty
Wheel size: 27.5in | Frame sizes: S, M, L | Weight: 13.5kg | Frame material: Carbon
Pros: Choose your own wheel size. Amazing value.
Cons: Only three frame sizes. No dropper post.
Canyon’s Dude walks the fine line between fat bike and Plus bike with 3.8in tyres on 27.5in wheels – a full inch narrower than some competitors. That means less floatation on soft surfaces, but a slightly more normal, versatile ride on dirt. However, sliding dropouts let you customise your wheels and tyres – run 26×4.8in or 29x3in as well as the stock 27.5×3.8in. Being a Canyon, it’s exceptionally well appointed, with a full carbon frame and fork as well as a 12-speed wide-range SRAM drivetrain for a surprisingly keen price. If you’re fat-curious, this could be the bike for you.
What are fat bikes for?
“Why?” is the wrong question. Fat bikes are all about “Why not?”
What are fat bikes for, though? That’s a surprisingly difficult question to answer. Although it is true that fat bikes were originally invented for riding across sand or snow, that isn’t the reason why fat bikes exist now. The vast majority of fat bikes are ridden on the normal trails that you ride any mountain bike on.
You can ride fat bike… anywhere. Fat bikes are first and foremost about grip. Traction tractors. The fat tyres aren’t really a substitute for, or alternative to, suspension. Don’t go for a fat bike if you’re looking for a suspension bike experience. Fat bikes aren’t best treated as bump soakers. They’re for hoovering up terrain. ‘Floatation’ is a commonly bandied about term.
Why ride a fat bike?
There is one simple answer. An answer that trumps all other answers: because you want to. You don’t have to justify it.
That said, the market for fat bikes is far from straightforward or free of tech. Once you go down the rabbit hole of fat bikes you’re quickly into the complicated compatibility-strewn world of Q-factors, hub widths, chainlines and super-precise PSI.
Initially, it’s almost not worth even thinking about tyre tread pattern and design. The sheer footprint of fat tyres is what generates the traction. Err on the side of minimal knobbles though. Once you’ve got a few rides under your belt, you can start to think about what sort of other tyre tread you may wish to try out.
As for sidewalls and tyre weight, don’t be tempted with the lightest tyres you can find. They just don’t ride very well. They wibble around and deflect like mad. They also offer no damping whatsoever to counter bike bobbing.
Tyre pressure is everything
Tyre pressure governs how the fat bike will interact with the ground. It is a very good idea to get yourself a digital pressure gauge. Big volume tyres run at MUCH lower pressure numbers than normal mountain bike tyres; fat bike tyres run at around 10psi. Up the pressure a couple of psi at a time for riding firmer trails. Lower it for looser or muddier conditions. A good starting point is 8psi. Suck it and see.
Try to remember to check your tyre pressure before every ride as some setups lose air quicker than you might think.
Hubs and bottom brackets
The elephant in the room of fat bikes. Hub and bottom bracket standards are all over the place. Because you can’t fit those oversized tyres into regular mountain bike frames and forks, this has resulted in a lack of consistent approach to hub widths and also bottom brackets (cranks have to be set wider apart to fit either side of the expanded rare stays).
It many it’s probably best to not worry too much about it. Whatever you go for you’ll be left stranded. There’ll be spares and upgrades for all standards for quite a while yet.
That said, if you want to leave the option of running a suspension fork at some point, get a fat bike with 150 x 15mm front hub.
The rear hub width that appears to becoming the most common is 197 x 12mm. In some ways this is a bit of shame as it leads to really special wide Q-factor cranks (think: John Wayne) but that’s the way it appears to be going.
Some notes about Q-factor. Regular mountain bikes have a Q-factor of around 170mm. Modern fat bikes are coming with Q-factors hovering around 200mm.
It may feel bizarre talking about suspension when dealing with fat bikes but, as we said above, a fat tyre is not an alternative to the best full suspension mountain bike. Suspension and fat tyres do two very different jobs. A suspension fat bike is not a pointless thing.
A 4in tyre is not an alternative 4in-travel suspension fork.
Fat tyres are about amount-of-rubber in contact with the ground. Fat tyres use their size to deform under pressure (from above and below) to increase the amount of tyre adhering to the trail. They aren’t there to absorb rough stuff.
Fat tyres are not for soaking up bumps (although they do soak up small trail buzz admittedly). Loads of people assume that’s what fat tyres do. It isn’t correct.
Think of fat tyres for traction and suspension for control. Suspension has damping. Suspension is still the thing for controlling the immediate after-effects of large external forces (bumps, hard corners, G-outs etc).
So, as with regular hardtail mountain bikes, feel free to go for one with a suspension fork. We’d actually strongly recommend it if you want a fat bike to be your only/main bike. RockShox and Manitou are the names to look out for here.
That said, if you’re merely fat-curious or want a fat bike to become part of your fleet of available mountain bikes, there’s a lot to be said for saving money (and weight and servicing) and going for a rigid fork fat bike.
Despite what anyone may try to tell you, frame material has only one effect on the bike: weight. There is simply no way that any inherent ride characteristic of the chosen frame material is detectable through 4 inches of rubber.
Go carbon if you have the funds and want to save weight. Go titanium if you have more money than sense and like the look. Otherwise just go for an aluminium or steel frame fat bike.
How floaty do you want your fat bike to ride? The principle choice here is 4in tyres or bigger-than-4in tyres. Not many riders are well served by tyres bigger than 4in.
Unless you genuinely are mainly riding on sand or snow, don’t get instantly sucked into the temptation of the fattest tyres possible. They’ll be insanely sluggish and bouncy and will quickly become not-fun. And fun is what this is all about.
4in tyre fat bikes offer the complete fat experience with hardly any drawbacks or compromise.
Rim widths range from anything 50mm up to crazy beamers of 100+mm wide. You really do need to match your tyre width to your rim width very carefully. It’s this aspect that can end up being costly if you dive in to purchasing a fat bike too eagerly without doing your research. Fat bike wheels aren’t cheap.
For 4in tyres you need to pair them with rims of between 60-80mm wide. For fat bikes with tyres wider than 4in, rim width is a complicated business where single millimetres have an pronounced effect. Needless to say, for 5in tyres we’d recommend not going over 100mm in rim width.
Unlike on regular mountain bikes, where we would always recommend tubeless, with fat bikes ‘going tubeless’ is easier said than done and the benefits are minimal at best. Sure it can save a bit of weight but not that much. And the extra heft of fat rubber is actually part of the ride experience and performance. WOOMPH-ing your way across the landscape is a big part of the experience.
So although you can go tubeless, it can be tricky getting tyres to seal and may require outlay on a tubeless tyre inflator.
Due to their snow bike heritage – and current wilderness bike wannabe status – you can sometimes find cable actuated disc brakes on fat bikes.
Not to beat about the bush, cable disc brakes suck. Their one and only advantage is that the can be mechanically/agriculturally bodge repaired if they go wrong in the middle of the Artic Circle. Are you going to be riding in the Arctic Circle? No. Get hydraulic disc brakes.
How much to spend on fat bike
You get what you pay for, as with all things in life. You will find fat bikes being knocked out for very tempting prices. Much like with niche bikes like fixies, singlespeeds and even arguably BMXs, the cheap option is very tempting. The problem is though, they won’t ride very nicely and they won’t last very well.
We’d strongly recommend looking at fat bikes nearer the £1,000-£2,000 mark. From a recognisable and reputable bike brand. And purchase it via a proper bike shop who will help you set it up and sort out obscure spares etc.