You’ve probably seen them, normal enough looking bikes out riding on your local trails – except for one glaring difference, giant tires! These are known as fat bikes, and they are becoming more and more popular amongst mountain bikers, especially those looking to chase their passion and keep moving in the cold winter months. What is the point of those massive tires? Read on to find out everything you need to know about the “Jeep” of mountain bikes.
Design differences between fat bikes versus regular mountain bikes
Tires
The most obvious difference between a fat bike and a regular mountain bike is the size of the tires, with fat bikes having fat tires ranging in width from 3.7 to 5 inches. By comparison, a normal mountain bike tire falls into the range of about 2 to 2.5 inches.
These fat tires make fat bikes look very different from typical mountain bikes. But what do the fat tires do?
In short, fat tires spread out the pressure imparted on the ground over a wider area, which helps to prevent them from digging into softer surfaces, like snow, sand and soft or damp trails. Spreading out the pressure imparted on the ground also provides for a larger contact patch which significantly improves the traction between the tires and the trail.
Riders experienced in fat biking often run lower tire pressures to further reduce the pressure imparted on the ground, especially if they’ll be riding in very soft conditions like fresh snow.
Depending on conditions, the PSI riders run in fat bike tires can vary from as low as 1 PSI in very soft conditions all the way up to 10+ PSI in firm conditions or on more solid surfaces like hard-packed dirt, rocks or pavement.
Suspension
Fat bikes typically have less suspension than an ordinary mountain bike, with most models coming standard with a rigid fork and no rear shock. A major reason for this is the fact that the larger, softer tires do a great job of soaking up many of the bumps you’ll come across on the trail.
This is also a way for fat bike manufacturers to save weight on the bikes, as fat bikes are already heavier than ordinary mountain bikes. The lack of mechanical suspension also helps to improve pedaling efficiency on climbs by not having pedal bob resulting from mechanical suspension, helping to offset the energy lost through the compression of the tires themselves.
Some fat bikes, especially more recent models, do have a suspension fork up front to further absorb impacts and allowing riders to push themselves further on their fat biking escapades. It is rare to see a fat bike with a rear shock, however.
Geometry
Head tube angle
Head tube angles on fat bikes are typically steeper when compared to ordinary mountain bikes. The head tube angle on a fat bike will typically be around 68 to 70 degrees, whereas the typical trail bike will be in the 65-to-67-degree range and the typical enduro bike will be slacker still with a head tube angle close to 64 degrees.
The steeper head tube angles on fat bikes help them to handle better at low speeds and on flat ground and keeps more weight over the front tire for better traction in slippery conditions.
Pedal width
One key difference between fat bikes and ordinary mountain bikes is the pedal width. The distance between your feet on the pedals needs to be further on a fat bike to accommodate the fat tires.
This can give the bike a bit of a different feel compared to ordinary MTBs. One disadvantage of the added pedal width is its easier for pedal strikes to occur.
Wheel size
Fat bike wheel size is normally 26 inches, with some as large as 27.5 inches. Because of their high-volume fat tires, their size is similar to a mountain bike with 29-inch wheels when inflated.
Weight
The fat tire and wide-rim design on fat bikes makes them heavier than an ordinary MTB.
The typical fat bike weighs in somewhere between 33 and 40 lbs. By comparison, normal mountain bikes are lighter, typically ranging from 28 to 32 lbs.
Because of the added weight from the fat tires and wide rims, fat bike manufacturers mostly take a minimalist approach to mechanical suspension to save weight by not having a rear shock and often not having a suspension fork up front either.
Riding experience on a fat bike compared to a regular mountain bike
Smoothness of ride
Tires aren’t normally what mountain bike riders think of when they think suspension. However, the soft, wide tires equipped on fat bikes do a great job of smoothing out many of the bumps you’ll come across on the trails, and act as their own form of suspension.
When fat biking, you can ride over most obstacles you encounter on the trails, and the tires will do a good job of absorbing the impact and maintaining traction. They do this by deforming on impact of obstacles which absorbs the force of whatever obstacle you hit.
By comparison, regular mountain bike tires create much harder impacts and this is a reason they will normally require a suspension fork and, at times, rear suspension to smooth out the ride.
Confidence on descents and technical features
For bikes without the typical suspension you may expect on a mountain bike, fat bikes are surprisingly capable on descents. The plushness of the ride and added traction provided by the wide, soft tires make these bikes sturdy and confidence inspiring when going downhill.
In the winter, on snowy, slippery trails, fat bikes really shine on the downhills. This is because you can carry much more speed than you otherwise would on descents thanks to the added traction allowing you to maintain control and stop easier.
That said, a fat bike will not replace purpose-built downhill or enduro bikes when it comes to speed and agility on the descents in dry conditions. Fat bikes can handle the ride and do so smoothly but are unlikely to win out in a race against downhill or enduro bikes. You also won’t want to be sending a rigid fat bike off of huge jumps and drops, but that doesn’t mean you can’t still have a blast on small and medium sized features!
Climbing ability
Fat bikes make for excellent climbers, due to the incredible traction provided by the wide tires and large contact patch, allowing you to climb on even some of the slipperiest surfaces.
The large tires also smooth out the bumpy parts of the climb to keep your momentum moving up the hill, and the steeper head tube angle helps maintain weight and traction on the front wheel while going uphill.
One downside to fat bikes on longer climbs is the extra weight compared to an ordinary MTB, which can make things a bit sluggish if you’ve got big hills to go up.
Roll speed
The extra traction provided by the fat tires comes at a cost unfortunately, which is that they reduce the roll speed of the tires as compared to an ordinary MTB. Speed and agility are not primary reasons people get into fat biking, and on flat ground the added traction and reduction to roll speed definitely reduces the efficiency of the ride.
On the plus side, this reduced efficiency makes fat biking an excellent workout!
When to use a fat bike
Weather
Snow and winter riding
One of the most popular reasons people get into fat biking is to be able to keep their riding going in the winter months. The wide, soft tires on a fat bike allow you to ride in conditions you may have never thought possible on a regular MTB.
While regular mountain bikes can ride on hard-packed snowy trails, they are no match for the massively increased traction of fat bikes. Regular MTBs also can’t really be used after a fresh snow fall, and typically those riders will wait until after the fat bikes have taken a few laps through the fresh snow to pack the trails down.
Fat bikes can almost float across even fresh snowfalls, especially when ridden with a lower PSI. They will ride faster on hard packed snow trails, as you’d expect, but are still adequate to pedal through fresh untouched snow. It is a real novelty to pedal through your favorite trails after a fresh snow fall and can be hard to believe you are even able to do it – this just adds to the fun and adventure!
Terrain
Fat bikes are well suited to lots of different types of terrain, and work well for climbing, descending, and flat ground. And as mentioned above, they are terrific for winter and snow riding.
Fat bikes handle bumpy trails well, and the fat tires feel plush and do a good job of absorbing most bumps, but as with everything, there is a limit. Typical fat bikes are not designed to handle massive drops.
Another type of terrain not normally associated with mountain biking is sand and beaches. If you have ever tried riding a regular MTB on soft sand, you know it doesn’t work very well because traditional MTB tires dig into the sand. Fat bikes prevent this and the wide tires float on top of the sand, allowing you to go riding up and down the beach.
Trail types
Fat bikes are very versatile and can tackle most trails you want to throw at them. They will be able to handle most everything at your local trail system except for the most extreme drops and jumps. They shine on snow covered trails, trails with variable and loose surfaces, on sand and everything in between.
One of the most fun aspects of fat biking is feeling like there are virtually no limits to where and what type of conditions you can ride in – if you can’t do something on a fat bike you probably can’t do it on a bike, period.
Pros and cons of fat bikes:
Pros
- Excellent traction, better than any standard MTB
- Ability to do winter riding and tackle snow-covered trails, even after a fresh snowfall
- Plush and smooth riding experience thanks to suspension provided by the large, soft tires
- Feeling that you can ride virtually anywhere
Cons
- Heavy compared to standard MTB
- Slower roll speed resulting from increased traction
- Not built for large features
Frequently asked questions
Fat bikes are easy to pedal and ride and they feel very stable even to new riders. Since fat bikes have wider tires, they provide more traction and stability, especially on snow and sand, and are easier to ride over this type of surface.
The downside is they are harder to ride fast compared to regular mountain bikes because of their weight and slower roll speed, and they take longer to get up to speed.
Fat bikes are good for a lot of things! They’re great for riding on sand, in the snow, and on other difficult terrain and surfaces because of their wider tires. Their large tires also provide a lot of cushioning, making them more comfortable to ride than many traditional mountain bikes.
Yes, you can use a fat bike on regular mountain bike trails. However, it’s important to remember that a fat bike is wider, heavier and a bit less maneuverable than a traditional mountain bike, so some of the narrower or more technical trails may be more difficult to ride on.
It depends on the width of the tires. The frame and fork of the mountain bike must be able to handle the wider tires. If you can’t go too wide with your tire width, then you’ll have to purchase a new frame and fork that are designed specifically for fat tires.
Most mountain bikes have a tire width of 2 to 2.5 inches. So, if you want to go with wider tires than that, you’ll need to find a frame and fork that are designed for fat tires which have a width of 3.7 to 5 inches.
Yes, especially if you enjoy riding in winter or on soft trails and surfaces. A fat bike is perfect for that because the large contact patch and volume of air in the tires provides excellent traction and keeps the bike on top of the surface instead of sinking in. The fat tires also absorb shocks and provide a comfortable ride on bumpy surfaces. Fat bikes allow you to keep your mountain biking going year-round!
Conclusion
Fat bikes are a blast to ride, and we hope you’ll give them a try. If you’re looking for an awesome new way to experience mountain biking, especially during the winter months, fat biking may be just what you’re after. There is something special about riding in conditions and on surfaces you would have never thought possible before trying them on a fat bike!