MOUNTAIN BIKES SUSPENSION – BUYERS GUIDE

Shaun George BOTS Guides

As you already know, the suspension system on a mountain bike is one of the most complex and most important components – besides the frame of course. Suspensions have existed in cycling culture for quite a few decades now. As time passes there are constant innovations and developments to make suspension systems lighter, stiffer, and perform better.

Chances are, your bike has a suspension system too. Hybrids and mountain bikes are currently the two main disciplines that share the need for a suspension system. Your bike either has a basic coil fork (most hybrids do) or an air fork (seen on mid-range & high-end MTBs). Either way, we’re going to take you through the fundamentals and different kinds of suspensions that you may need for your next upgrade.

If you’re new to mountain biking, don’t worry, we’ll be covering all the basics on what amount of suspension travel you need for each type of riding and what type of fork and shock is most suitable for you.

If you’re an experienced rider and you’re looking to upgrade your fork or shock to either replace worn units or gain a performance advantage then you’ll need to look carefully at what suits both your bike and your riding style.

WHAT IS A FORK?

Almost all mountain bikes are equipped with front suspension, as well as some hybrid or “commuter” bikes and kids’ bikes.

A suspension fork comprises of the two tubular legs at the front of your bikes. Forks have what’s called the “upper legs” that slide within a one-piece “lower leg” assembly. The forks not only give you control and comfort but also help you steer better by keeping you on line.

Suspension systems on mountain bikes offers a range of adjustments to fine-tune the riding experience. Variations include the amount of travel, rebound, compression and plushness your fork gives you.

Hybrid/commuter bikes on the other hand offer basic comfort and functionality with minimal or no adjustments at all.

FRONT FORK ANATOMY

MTB front fork anatomy
Front fork anatomy

1. STEERER TUBE: This part of the fork connects your bike to the fork. On MTBs, most steer tubes are tapered, meaning the base of the tube is wider than the top – this allows for increased stiffness and stability.

2. CROWN: The crown is essentially a brace and support structure that connects your fork’s steer tube to its stanchions.

3. STANCHIONS: The stanchions are the pieces of tubing that actually slide into your forks lowers. The stanchions internally house the coil spring (or air) as well as the damper.

4. ARCH: The arch is simply a support structure that helps with stiffness and rigidity between the two stanchion legs.

5. LOWERS: The lowers connect your fork to your wheel and move upwards during compression.  Lowers also house the bushings and grease/lubricating oil, which make contact with your uppers and lubricate them.

TYPES OF FORKS

Attributes Coil SpringAir Spring
PerformanceGood to very goodVery good
AdjustmentsLessMore
ReliabilityExcellentVery good
Maintenance costsLowerHigher

1. COIL SPRING

This is often found on very basic bicycles. Here, the spring is essentially a wound steel coil that provides a linear compression rate, giving smooth, consistent impact absorption over the range of spring travel.

Coil springs are available with different resistance rates and are matched to the riders riding style and weight. If your coil spring feels too soft or too firm for your weight and riding style—and the available adjustments have not corrected the issue. Then you can look at going for a softer/stiffer coil to match your needs.

2. AIR SPRING FORKS

These kinds of forks don’t come cheap and are often only found on mid-range and high-end forks. Instead of a coil here, there is pressurized air in a chamber.

The main advantage of an air-sprung fork is its lighter weight, and progressive compression rate which translates to less effort when pedaling uphill and a softer feel in the initial part of travel which then gets stiffer as more compression is applied.

WHAT TO CONSIDER BEFORE BUYING A FORK

1. TRAVEL

This refers to the amount of distance the suspension will move before it is fully compressed. This is an area many people pay a lot of attention to, and rightfully so.

The amount of travel will dictate what your fork can handle and how much of the rough stuff it can take. This doesn’t necessarily mean that you need to go in for a fork with a ridiculous amount of travel (180-200mm).

Suspension may be referred to as short or long travel:

  • Short-travel suspension (less than 120mm) suspension provides an all-round riding performance with an emphasis on smooth trails and climbing efficiency.
  • Long-travel suspension (greater than 130mm) is best for descending rough terrain at high speeds with greater control. The longer the front travel, the more the emphasis is toward descending gnarlier terrain.
Suspension travel (Millimeters)Type of Bike (riding style)
60 – 80mmHybrid bikes
100 – 120mmCross country/Trail mountain bikes
120 – 160mmAll-mountain/Enduro mountain bikes
180 – 200mm Enduro/Downhill mountain bikes

2. CONSTRUCTION

There isn’t too much variability here but it’s worth mentioning that cheaping out on a very basic coil fork is not ideal for even the most basic riding requirements. Construction in those forks is under-par to say the least. Your fork will also dictate how responsively the bike steers, brakes, and rides over rough terrain.

The lower legs on the fork are a one-piece with an integrated brace stiffening up the structure and keeping the weight low. The upper legs have a bonded or one-piece crown and steerer, this, along with a stiff fork-to-wheel interface such as a bolt through axle gives very accurate steering, less flex, more grip, and better braking control. These features are some of the industry standards that are followed for even entry-level forks these days.

3. STANCHION DIAMETER

The stanchions or the two parallel tubes above the lower legs are responsible for overall fork stiffness. The diameter of the stanchion tubes affects lateral stiffness. A narrow tube will flex more under the same force than a wider tube. Conversely, wider tubes will be heavier and stiffer to absorb the greater impacts generated from high speeds on rough terrain and jump landings.

Bike choose a fork that offers the appropriate diameter and stiffness for the intended riding purpose of a particular bike model.

Hybrid bikes usually feature 28-30mm stanchion as their riding conditions aren’t all that demanding. Downhill bikes on the other hand will feature up to 38-40mm stanchions.

FORK ADJUSTABILITY

1. LOCKOUT: This a feature you will see on even some very basic hybrid front forks. You will often notice an on/off kind of turn-key on top of the stanchions of a fork. This is used to lock out the fork, which eliminates the travel. This minimizes your energy loss when riding flat, paved surfaces or on long uphill climbs on smooth dirt surfaces.

On some forks there is a handlebar-mounted lever to remotely control the lockout via a cable (usually seen on XC bikes).

2. PRELOAD: Another common feature seen on basic coil forks is preload. Preload is represented by a knob on top of one of the stanchions to allow for the unweighted tension on the spring to be increased or decreased. Increase the preload if the fork feels too spongy and vice versa.

3. REBOUND: The rebound knob is seen only on mid-range and high-end forks. It is universally represented by a “red knob” under the left/right lower leg of a fork. As the name suggests. It controls the speed at which the fork re-extends after compression. This reduces the bounciness usually associated with a spring. 

HOW TO UPGRADE YOUR FORK?

1. STEERER TUBE: There are two types of classifications for a steerer tube these days. You’ve either got a standard steerer or a tapered steerer (this depends on your headtube). A standard steerer tube is straight with a 1-1/8” diameter tube. Old bikes may have a 1” diameter tube; newer bikes often have a tapered/oversized steerer tube. Make sure your new fork has a compatible steerer tube.

2. TRAVEL: Bicycle manufacturers design bike frames with certain suspension travel ranges in mind. The amount of travel will change the handling characteristics of the bike so be careful with your choice.

An older mountain bike may have an 80mm fork, which is hard to find now. A 100mm fork may be an acceptable replacement, but a 120mm fork will probably alter the bike geometry significantly to the detriment of safe and stable handling.

Always check with your bike manufacturer for replacement fork recommendations.

3. BRAKE MOUNT: Disc brakes on mountain bikes and even many hybrids are common now. If you want to replace a fork that has rim brake mounts, your choices will be limited to some very basic suspension models unless you upgrade your wheel and brakes as well.

4. AXLE TYPE: More common now is the Thru-axle standard that is seen on more high-end MTBs these days. You need to find out, does your front wheel have a standard 9mm quick-release? Or a 15mm or 20mm Thru-axle? Choose the correct axle dropout size for your wheel.

Alternatively, you could change your front wheel to upgrade to a Thru-axle standard if you wish to.

REAR SUSPENSION

The rear suspension, also referred to as a “shock”  is only found on full-suspension mountain bikes. The shock allows the rear wheel to soak up impacts, helping to keep the tire in contact with the ground, increasing rider control, traction and decreasing rider fatigue.

The shock is located in the bike’s rear triangle – the area in between the front and rear wheel. It will have one or more pivot points to enable the wheel to travel through a range of motion.

The shock has one end attached to the main triangle and one end attached to the pivoting rear triangle. The thing about rear shocks is that manufacturers have the ability to create almost any kind of linkage system, each with its own pros and cons. The bottom line is that they all work well, and the average recreational rider is unlikely to notice significant differences in suspension performance.

WHEEL TRAVEL VS STROKE TRAVEL

Think of travel as the axle’s range of motion. For the front wheel, travel is only a function of the fork’s stroke. This means that, for forks, stroke and travel are the same thing.

There’s more to the equation for the rear suspension, since the rear axle’s range of motion, or travel, is dictated by the bike’s linkage. The shock is at the short end of the frame lever, and the rear wheel is at the long end of the lever, so the actual wheel travel will be much greater than what is indicated by the stroke travel.

That’s right! Shocks don’t have travel–they have stroke, which is the distance the stanchion can move within the shock’s body. It’s because of this that it’s possible for two bikes that use shocks with the same stroke length, but have different amounts of travel.

SUSPENSION CARE & MAINTENANCE

Suspension units are expensive to replace which is why it’s important to take care of them.

A suspension system’s lifespan can be extended by having periodic service performed by a suspension specialist. If you ride regularly, have your suspension serviced annually or after 70-100 hours of riding time. Regular service will also prolong the life of your bike frame.

  • Clean the stanchions after every ride with a soft cloth and mild cleaning solution. Apply a light coating of stanchion lube around the dust seal at the top of the lower legs to keep things smooth.
  • Prevent or reduce scratches to the stanchions. If these get nicked from debris then the rough edges can tear up the dust seal and bushings as it slides past, diminishing the performance and life of the suspension.

Do go through our blog post on – D.I.Y BASIC BICYCLE SUSPENSION MAINTENANCE


We hope we covered the basics of front and rear suspensions for all you folk out there. Do let us know if you think we missed out on something.

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