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A complete guide to choosing your mountain bike

Find out how to choose the perfect mountain bike for your needs. Advice on features, terrain types and budget options.

The kind of bike you choose depends entirely on the kind of riding you intend to do. Putting in kilometres on easy trails or chasing thrills on steep descents. From cross-country to all-mountain, and knowing which parts best suit your riding style, here's your guide to choosing a modern mountain bike this season. 

How To Choose a Mountain Bike : What Size Do I Need

The Different Types of Mountain Bikes


Most similar in makeup to road bikes, these bikes are often more lightweight than trail bikes and offer better pedal efficiency. These bikes are better suited to fast-paced riding opposed to rough terrain. Cross-country bikes can be both hardtail or full-suspension and typically have narrower tires for reduced resistance and enhanced speed.

If pedalling performance is your top concern in a bike, choose a cross-country design for optimal endurance and an efficient ride.


Similar to trail bikes, all-mountain bikes are best for longer climbs and more challenging descents. This type of bike is lightweight enough to pedal uphill while being sturdy enough to stabilize steep descents on technical trails.

Enduro mountain bikes

Named for a type of racing where riders are timed on their descent, but not the climbs. These bikes therefore have a lower head angle, allowing riders to take on steep and rough technical descents while maintaining the efficiency needed for long climbs back to the top. The balanced suspension is ideal for rocky and rugged, technically-demanding trails, but can be used on a diverse variety of terrain.

Downhill Mountain Bikes

These bikes are strictly for descents and downhill riding, given their short pedalling range. As for frame design, this type of mountain bike offers high travel, these bikes have heavy, sturdy frames that are perfect for jumps, wooden ramps, rocky terrain and steep drops.

The heavy-duty suspension of downhill bikes absorbs impact and maintains stability in the most aggressive terrain. These types of bikes are best-suited to riders that frequent lift-serviced bike parks.

Fat bikes

Characterized by oversized tires ranging from 3.7 to 5+ inches. Tires like these provide traction on sand and snow. While fat-tire bikes can be used on trails, their extra weight and bulky handling can get tiring.

How to Choose the Size and Geometry of Your Mountain Bike?

The easiest way to determine what size bike you need is by comparing your height to the frame size. Body proportions are also important to consider for things like reach and standover height. 

Reach: Distance from the saddle to the barsA bike with a longer reach will have a longer wheelbase. This provides stability, particularly on high-speed descents.

Head angle: Angle between the ground and the head tube

“Slack” angle = lower number, more stable at high speeds, more comfortable on downhill terrain. Steering is not as precise and requires more control from the rider on uphill climbs.

“Steep” angle = front wheel stays planted, nimble steering on climbs, though more unstable on fast descents.The greater the angle, the faster the bike will turn and better it will climb. A lower head angle will often mean the bike is more stable downhill, but steering will take more effort while climbing.

How To Choose a Mountain Bike : What Size Do I Need
How To Choose a Mountain Bike : What Size Do I Need

Which Mountain Bike Should I Choose for My Child?

The bike that’s right for your child will depend on their ability and ease when riding.

The basics to consider include standover height (the height at which your child can comfortably straddle the bike with both feet on the ground).

Wheel size: bigger wheels maneuver obstacles better and don’t require as much effort to keep momentum while riding.

Seat height: your child must be able to touch the balls of their feet on the ground while in the saddle.

Reach: Your child should be able to comfortably reach the handlebars while sitting on the seat, elbows bent slightly and able to easily reach the gear shift and brakes.

Speak to one of our experts in store to help you decide which bike is best for your child.

How To Choose a Mountain Bike : What Size Do I Need

Suspension and damping

Hardtail vs. Full-Suspension Mountain Bikes

Hardtail bikes are more efficient while pedalling and faster on climbs, though they do not offer rear suspension. As they are lightweight, these bikes are better for beginners on easy terrain and can be good for cross-country racing. Plus, hardtail bikes are easier to maintain.

Conversely, full-suspension bikes are more versatile, being faster on difficult, obstacle-heavy trails. Offering increased stability on descents, these bikes are a good choice for any type of racing.

Damping: controls the rebound of the bike on jumps and impacts.

Full suspension: Damping on both the front (fork) and back (rear shock).

Hardtail: Only front suspension.

Shock Selection for Comfort and Control : Air vs. Coil systems

Air shocks are more popular among mountain bikes, powered by a spring of compressed air versus the coil shock made of a wound metal spring.

Coil shocks are common for downhill bikes as they are more sensitive, able to react faster to the high-speed impact of downhill terrain.

How To Choose a Mountain Bike : What Size Do I Need

Frame components and materials

Aluminum vs. Carbon Frames

Carbon fibre: Used for its durability and strength, paired with being lightweight, carbon fibre is typically found on higher-end bikes. However, carbon bikes can be more fragile than Aluminum.

Aluminum frames: While less expensive than carbon, aluminum frames are heavier. Strong and stiff, aluminum is a great option for everyday riders.

As a common rule, the more lightweight a bike is in materials and composition, the more expensive it will be. Steel is another inexpensive frame material, though it is considerably heavier for a mountain bike.

Importance of Component Quality

Wheels and Tires: Sizes and Characteristics

Wheel size:
Diameters: 27.5 inches (aggressive trail and downhill) or 29 inches (cross-country and trail)

27.5-inch wheels wheels provide are lighter than 29s and offer better acceleration and maneuverability. Alternatively, 29-inch offer better traction and attack angles. Taller riders should choose 29” wheels.

Choose bigger rims for long-distance riding and smaller, stronger rims for rugged terrain.

How To Choose a Mountain Bike : What Size Do I Need

Brakes and drivetrain

Disc brakes:

Disc brakes perform better in all types of weather, unaffected by rain or snowy terrain. Unlike v-brakes, disc brakes will not wear on the rims of the tires over time. While disc brakes are easier to install and make removing the tires easier, they tend to be heavier and more expensive than v-brakes while also adding strain on the spokes. Disc brakes are not universally compatible, depending on the fork of the bike.


Long being the go-to for bikes, v-brakes (or rim brakes) are far more affordable and easier to maintain and replace. However, v-brakes will wear on the tires overtime and braking performance is affected by snow, mud and rain.

How To Choose a Mountain Bike : What Size Do I Need

Drive Systems and Sprockets

Drive systems: The parts that work together to propel the bike. This includes a crankset, categorized by their number of chainrings — triple, double and single.

Bottom bracket, cassette and chains: Determined by the number of gears on the bike.

Sprockets: The individual components of a cassette that work together to move the chain between the cogs. A well-working cassette can reduce shifting time and improve performance.

Derailleurs and Shifters

Derailleurs: Move the chain between cogs on the cassette and chainrings on the crankset.

Shifters: Used to operate a bike’s derailleurs and shift gears on the bike. There are trigger shifters and grip shifters. Trigger shifters are easier to use as the require only one finger, leaving your hand free for braking, whereas grip shifters are ideal for cross-country riding as you can quickly shift across gears of the cassette.

How To Choose a Mountain Bike : What Size Do I Need

Budget and Prices

The amount of money you spend on a mountain bike depends on the level and frequency of riding you're going to do. Mountain bikes can range from $400 to over $5000. Having quality parts can make a difference, but they do come at a price.

For beginner and intermediate riders, finding a bike that fits you within an affordable range is key. Decathlon offers a range of bikes suitable for all levels of riders.

This affordable mountain bike is a great start for new riders.

How To Choose a Mountain Bike : What Size Do I Need

Accessories and Complementary Equipment

Beyond the bike, it's important to consider the equipment you need to practice mountain biking both comfortably and safely. Don't forget to always wear a helmet!

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