First, we considered what makes a mountain bike short (rather than a road bike short or just an athletic short). We define mountain bike shorts as non-form-fitting baggy shorts which provide more protection and features than tight lycra-style road shorts. The thing that separated these shorts from other types of athletic shorts is a chamois pad attached to a form-fitting liner worn beneath the outer short and features tailored towards making biking more comfortable.
Style of Riding
When shopping for a new pair of mountain bike shorts, first consider what type of riding you will be doing the most. "Mountain Biking" is a broad term which covers everything from lycra clad cross-country racing to hucking huge drops at the Red Bull Rampage in full body armor. Most riders have a pretty good idea of what type of riding they prefer, which also dictates their bike selection. Here is a quick breakdown and some ideas of how the shorts we tested fits with each riding kit.
Cross-country riding is typically done on smoother trails and involves a lot of pedaling in the saddle. Bikes designed for this type of riding usually have four inches or less of travel in the front and rear. The twenty-nine-inch wheel size is common to cross-country oriented bikes, as are hard tails. Cross-country riders will want lighter, less restrictive shorts which maximize pedal efficiency and ventilation. Protection and durability are not too important for this type of riding. Of the shorts we tested, we think that the Dakine Boundary and Kitsbow A/M are the best shorts for this type of riding. If you are a privateer racing cross-country you should probably consider a road-style lycra short since no baggy can match the range of motion and aerodynamics of these form fitting shorts. Check out our Road Bike Short Review for the best in this category. Inversely, if you simply can't stand form-fitting lycra, look for a lighter cross-country oriented short for road riding.
Enduro is the new hot word in mountain biking these days. While the definition of what enduro actually is may vary, it involves riding up as well as riding down technical terrain. Enduro somewhat takes the place of what used to be referred to as trail and all-mountain riding and might be best summarized by calling it "do-it-all" mountain biking. Five and six-inch travel full-suspension bikes fall into this category. Along with this new title for what most people have always just called "mountain biking" has come the return of the 27.5" or 650b wheel size which sits right between 29" and 26". Whether you are buying this wheel size or not, you should look for shorts that balance protection with the pedal ability and do-it-all features for this type of riding. Some shorts to consider would be the Zoic Ether Shorts + Liner or our absolute favorite, the 100% Airmatic both of which will work with kneepads whether you wear them just for the descent or all the time.
Downhill is all about the down and is best done on a slack 8-inch travel bike with a dual crown fork. Whether you are riding machine groomed, lift-assisted trails at the ski area or Northshore style stunts, downhill riding requires more protection. Full face helmets, goggles, neck braces, elbow and knee pads are a good idea.
Shorts for downhill riding should be long and have large enough leg openings to fit over the tops of kneepads. Durability is also important for this style of riding since crashing in gnarly terrain is more common. Of the shorts we tested, the Troy Lee Ruckus is best suited for this type of riding since it has a long inseam length and large leg openings to accommodate knee pads while the stretch fabric is both durable and protective. For full blown bike park downhill riding where you spend much more time out of the saddle than in it, you may want a heavier downhill specific short that does not have a liner short or chamois.
A chamois is a piece of padding placed in the area where your body contacts the saddle. Bicycling chamois were once made from smooth leather, but are now made from modern synthetic materials. The chamois serves to pad your undercarriage from the saddle and prevent chaffing. A chamois is what makes a bike short a bike short. The one exception to this being purpose built downhill mountain bike shorts which are aimed at riding predominately out of the saddle. These shorts often do not include a chamois and are targeted at a very specific genre of cycling.
Not all of the shorts we tested have an included liner short with a chamois pad. You can purchase a liner short separately when needed, and often this results in a higher quality chamois than the ones that are included with mountain bike shorts, though this method it is more expensive than buying both in one package. With that said some shorts like the 100% Airmatic include a stellar liner short that is on par with any aftermarket chamois liner available.
All of the pads we tested are made of foam. A well-articulated shape that matches the shape of the body in a seated position is the first thing we look for in a chamois. We also prefer chamois with dense padding, multiple thickness zones, and a smooth, seam-free cover made from wicking synthetic material. It is important that the chamois is positioned correctly by the short to be between the rider and the saddle when in the seated position. Mountain bikers typically pedal in a more upright position than road bikers. The contact between rider and saddle is more posterior because of the more upright position, and the chamois of a good mountain short should also be sewn into the short slightly more towards the rear of the short.
Mountain bike shorts are available with a variety of added features. Again, we recommend that you first consider what type of riding you are going to do most often and what type of features you need for that type of riding. We recommend buying a short with features you will use and nothing more. Unused bells and whistles are likely to just get in the way and increase the cost of a short.
For cross-country and enduro riders who always wear a hydration pack, shorts with pockets may not be necessary. However, more and more riders in all disciplines are choosing to ride without a pack for better weight distribution and a more enjoyable ride. So if you would like to forgo the pack, you will want a short with a least a few zippered pockets to secure a bike tool, phone, and some food. Regardless of what type of riding you are doing, we recommend pockets that securely close with a zipper rather than velcro or nothing at all. We don't recommend carrying anything more valuable than an energy gel in a non-zippered pocket when mountain biking since items are likely to bounce out unnoticed as you scream through a rock garden.
All of the shorts we tested also had some sort of waist adjustment method which allows you to fine-tune the fit. This is important in making sure the shorts stay in place while riding hard. The most common, and our preferred method, of waist adjustment is by velcro tabs or a hook and loop system on the outside of the waistband. If those tabs are placed on the inside of the waist, then you can't adjust them on the fly. If the tabs are hidden inside the waistband, then they are less prone to snagging but are more difficult to adjust perfectly and cannot be adjusted without unbuttoning the short. We also tested shorts that use a drawstring and cord lock, which we do not recommend.
Just like any piece of clothing, getting the right size is as important as any other attribute. We tested all of the shorts in a size medium or 32" inseam, depending on how they were labeled by the manufacturer. All of the shorts we tested fit most riders with up to a 34" waist and down to a 30" waist due to the waist adjustment mechanism.
You get what you pay for right? There is some truth to this statement, but bargains like the Zoic Ether do exist that defy mantra. If you are just starting out with the sport then a short like the Ether makes a lot of sense, they are affordable and will allow you to evaluate what you value in a pair of shorts prior to spending a fortune on something like the Kitsbow A/M.
We hope that our research and testing helps you choose the best pair of shorts for your riding style and needs. Options are endless but following the basic guidelines we have laid out can really help with making a solid purchase.