Define Your Riding Style and Suspension Travel

The first step is to be honest about the type of riding you do. Full suspension mountain bikes are categorised by their intended use, which is closely linked to the amount of suspension 'travel' they have (how much the wheels can move up and down). More travel provides more cushioning for big impacts but can be less efficient on climbs.

• Cross-Country (XC): Typically 100-120mm of travel. These bikes prioritise light weight and climbing efficiency for fast, less technical terrain.
• Trail: Typically 120-150mm of travel. This is the most versatile category, designed to be a capable all-rounder that can handle climbs, descents, and varied technical trails effectively. Most riders fit well into this category.
• Enduro / All-Mountain: Typically 150-180mm of travel. These bikes are built for aggressive descending on steep, technical tracks but can still be pedalled back to the top of the hill.
• Downhill (DH): Typically 180-200mm+ of travel. These are highly specialised bikes designed only for lift- or shuttle-assisted descents on the most extreme terrain. They do not climb well.

Choose the category that matches at least 80% of your riding. Buying an Enduro bike for gentle woodland trails will result in a slow, cumbersome experience, just as taking an XC bike down a downhill track can be dangerous.

Understand Key Frame Geometry Numbers

A bike's geometry chart can look like a complex spreadsheet, but a few key numbers tell you most of what you need to know about its handling characteristics. Understanding these will help you compare bikes more effectively than looking at components alone.

• Head Tube Angle: This is the angle of the front fork relative to the ground. A 'slacker' (smaller number, e.g., 64°) angle makes the bike more stable at high speeds and on steep descents. A 'steeper' (larger number, e.g., 67°) angle provides quicker, more responsive steering on climbs and flat terrain.
• Reach: This is the horizontal distance from the centre of the bottom bracket to the centre of the head tube. It's a key indicator of how long the bike will feel when you're standing up on the pedals. Compare reach numbers for bikes of the same size (e.g., 'Large') to understand their relative fit.
• Seat Tube Angle: This is the angle of the seat tube. A 'steeper' (larger number, e.g., 77°) angle places your hips more directly over the pedals, which is a much more efficient and comfortable position for climbing. This is a huge benefit of modern full suspension bikes.

Evaluate Suspension Linkage Designs

The way the rear wheel attaches to the main frame is called the suspension linkage. Different brands use patented designs, but they all aim to control how the suspension behaves during pedalling, braking, and absorbing bumps. While the nuances are complex, it's helpful to know the basics.

Common designs include the Horst Link (Four-Bar), Virtual Pivot Point (VPP), and various Single Pivot evolutions. Instead of becoming an expert, your goal should be to read reviews from reputable sources that describe the characteristics of a specific bike's design. Does it pedal efficiently without excessive movement ('bob')? Does the suspension remain active and smooth under braking? A test ride is the ultimate way to feel the difference.

Choose Your Wheel Size

The debate between wheel sizes has largely settled, leaving riders with excellent options tailored to different priorities.

• 29-inch ("29er"): These larger wheels roll over obstacles more easily and carry momentum better, making them great for speed and technical climbing. They can sometimes feel less nimble in very tight corners.
• 27.5-inch (or "650b"): These smaller wheels are generally more agile, playful, and easier to flick around corners. They accelerate quickly but may not roll over chunky terrain as smoothly as a 29er.
• Mixed ("Mullet" or "MX"): This setup uses a 29-inch wheel at the front for rollover and grip, with a 27.5-inch wheel at the rear for agility and clearance. It's an increasingly popular configuration, especially on Enduro bikes.

Your choice will depend on your riding style and height. Taller riders often gravitate towards 29ers, while shorter riders might prefer the fit of a 27.5-inch bike. The best approach is to test ride different configurations if possible.

Perform an Initial Cockpit Setup

Once you have your bike, the first step is to adjust the contact points to fit your body. This is a basic ergonomic setup you can do at home.

1. Saddle Height: With your heel on the pedal at its lowest point, your leg should be almost completely straight. This translates to a slight bend in your knee when you're properly pedalling with the ball of your foot. If you have a dropper seatpost, set this height for its fully extended position.
2. Handlebar Roll: Loosen the stem bolts and sit on the bike in your riding position. Roll the handlebars forwards or backwards until your wrists are in a comfortable, neutral position. The 'upsweep' (vertical bend) and 'backsweep' (horizontal bend) of the bars should feel natural.
3. Brake Lever Position: Loosen the brake lever clamps. Position them so you can comfortably operate them with your index finger without having to change your grip on the handlebars. Angle them downwards so your wrists are straight from your forearm to your fingers when in your attack position (standing on the pedals).

Set Your Suspension Sag

This is the most important step in setting up a full suspension bike. Sag is the amount the suspension compresses under your static weight. Setting it correctly ensures the suspension can extend into dips as well as compress over bumps. You will need your shock pump and a ruler or tape measure.

1. Put on all your regular riding gear (helmet, shoes, backpack with water) to get your accurate riding weight.
2. For the rear shock, push the rubber O-ring on the shock's shaft up against the air can's seal. Carefully sit on the bike in your normal riding position without bouncing. Step off the bike gently to avoid compressing the shock further.
3. Measure the distance the O-ring has moved. Divide this number by the shock's total stroke length (you can find this on the manufacturer's website). This gives you your sag percentage. For most trail bikes, aim for 25-30% sag.
4. If sag is more than 30%, add air with the shock pump. If it's less than 25%, release a small amount of air. Repeat until you hit the target.
5. Follow the exact same process for the front fork. The recommended sag is usually a little less, around 15-25%.

Adjust Rebound and Compression Damping

Damping controls the speed at which your suspension compresses and extends. It's what keeps the bike from feeling like an uncontrolled pogo stick.

• Rebound Damping (usually a red dial): This controls how quickly the suspension returns to its full length after a compression. Too fast, and the bike will feel bouncy and unstable. Too slow, and the suspension won't recover in time for the next bump, causing it to 'pack down' and feel harsh.
• Compression Damping (usually a blue dial or lever): This controls how easily the suspension compresses. Many forks and shocks have a lever for 'Open', 'Pedal', and 'Firm'/'Lock' modes. Open is for descending, Pedal adds stability for smoother trails or climbing, and Firm is for roads.

To set a baseline for rebound: Turn the red rebound dial fully to the closed position (slowest, usually clockwise). Then turn it back, counting the clicks. Start about one-third of the way out from fully closed. A good test is to push down hard on the suspension and see how it returns. It should return quickly but stop without bouncing or over-shooting. Adjust one or two clicks at a time until it feels controlled.