What You Need to Know Before Buying a Suspension Fork

Upgrading your mountain bike's forks with brand new suspension forks can be one of the best things you can do to improve your biking experience in tough trails. Not only do suspension forks absorb harsh impacts, but it will also allow your bike's front wheel to track the ground far more accurately, and as a result, provide you with improved stability and grip. But before you decide on the best suspension fork, there are a couple of important factors to consider.

Mountain bikes come with 29-inch, 27.5-inch and 26-inch wheels, each of which requires a specific fork size. There aren't any cryptic standards or complicated measurements involved in this part of deciding, so you just need to narrow down your search to the wheel size that your bike has. Once you figure out the size of the wheels, you need to figure out the axle standard, and pick a fork with dropouts that match it.

There are a couple of different axle standards, the most common one being the QR axle, which uses a 9mm hollow axle that features a 5mm quick-release skewer. QR axles can be found on most budget to mid-level bikes. The other popular axle standard is the bolt-through axle, which is typically available in 20mm or 15mm diameter, and the axles comes as part of the fork instead of the wheel. These axles slide through one fork leg through the hub and out the other fork leg, and they're secured using a quick-release clamp.

That being said, take out your bike's current front wheel and measure its axle diameter so that you can further narrow down your suspension fork choices. Worth noting is that some wheel manufacturers offer aftermarket axle cups that can be swapped into their hubs, thus allowing you to go up or down on axle size.

And lastly, you need to work out the head tube diameter of your bike's frame head tube, so that you can match it with the appropriate fork steerer tube diameter. The standard has been 1 1/8-inches for a long time, but some modern bikes now feature larger 1.5-inch head tubes or even tapered tubes which have a larger tube at the bottom (1.5-inches) than the top (1 1/8"). If your bike has a tapered tube, you'll also need a fork with a tapered steerer tube to match it. Worth noting is that you can fit a straight steerer form through a tapered head tube if you use a reducer cup for the larger lower part of the headset to make it fit.