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Mountain biking, with its thrilling blend of adventure and physical engagement, is a hobby loved by children and adults alike. However, getting started on this exciting pursuit can often be met with a daunting task: choosing the right mountain bike size.  

While kids' mountain bikes offer a relatively straightforward sizing process, the realm of adult mountain bikes presents a more complex array of options, typically categorised as Small, Medium, and Large.  

In this comprehensive guide, we delve into the intricacies of mountain bike sizing, shedding light on the various factors that influence the perfect fit.  

Kids Mountain Bike Sizing

Unlike adult mountain bikes, sizing kids' mountain bikes is a relatively straightforward process. 

Typically, kids' mountain bikes are categorised by wheel size, ranging from 18-inch for young children to 26-inch for older children.   

There are however some models which offer more than one frame size, such as the Cube Aim series. The Aim XS has a 14 inch frame, and the Aim S has a 16 inch frame.  

To determine the appropriate size for your child, you can view our kids mountain bike category page and check the recommend inner leg measurement below each bike.   

As children grow, they can progress to larger wheel sizes, and with Bike Club you will be able to easily exchange their current bike for a larger one.  

children riding frog mtbs - Bike Club

Kids Mountain Bikes Available 

Our wide selection of kids' mountain bikes caters to a diverse range of ages and skill levels. From Cube mountain bikes like the Cubie 180 SLX, Acid Series, Aim S & XS, to Frog MTB series and the Orbea DIRT Series, we have the perfect bike to match your child's needs and aspirations. 

Brand Model Wheel (") Weight (kg) Inner Leg (cm) Age Range
Cube Cubie 180 SLX 18 7 45 - 52 4 to 6
Cube Acid 200 SLX 20 8.2 49 - 57 5 to 7
Woom OFF 4 20 8 54 - 62 6 to 8
Cube Acid 240 SLX 24 9.5 52 - 63 7 to 9
Cube Acid 240 Disc 24 11.9 52 - 63 7 to 10
Frog MTB 62 24 11.3 58 - 65 8 to 10
Cube Acid 260 Disc 26 13.9 57 to 66 8 to 12
Frog MTB 69 26 11.4 63 to 70 10 to 12
Frog MTB 72 26 11.5 67 to 81 10 to 14
Cube Access WS XS 27.5 14.9 65 to 72 8 to 12
Cube Aim XS 27.5 14.9 65 to 72 8 to 12
Cube Aim S 27.5 14.9 71 to 82 11 to 16+


Adult Mountain Bike Sizing 

While kids' mountain bike sizing is relatively straightforward, adult mountain bikes often come in three sizes Small, Medium, and Large. These sizes correspond to different frame sizes, which influence the overall geometry of the bike and its suitability for riders of varying heights and leg lengths. 

To determine the ideal frame size for your needs, it's crucial to consider your inside leg measurement, which is the distance from the ground to the top of your inner thigh when standing with your feet flat on the floor.  

To simplify this process, we provide recommended inside leg measurements for each adult mountain bike on our product pages. Simply measure your inside leg and compare it to the range specified for the bike you're considering. This will provide a clear indication of whether the bike is the right fit for you. 

You can also check our table below.  

forme black rocks mountain bike - bike club

Adult Mountain Bikes Available 

Forme mountain bikes seamlessly blend performance, comfort, and durability for a great cycling experience. Whether you're conquering challenging trails on your Curbar Pro 27 S or navigating tricky terrains on your Black Rocks HT 1 M, Forme has the perfect bike to match your riding aspirations. 

The lightweight yet robust frames are engineered to tackle any obstacle, with ergonomic design for a natural riding posture. The meticulous components and premium materials guarantee years of reliable performance which is why they are perfect for our circular model.  

Brand Model Wheel (") Frame Size (") Weight (kg) Inner Leg (cm) Height (cm) Age Range
Forme Curbar Pro 27 S 27.5 14 14.5 64 to 74 156 - 168 16+
Forme Curbar Pro 27 M 27.5 17 14.5 70 to 78 168 - 178 16+
Forme Black Rocks HT 1 S 29 16.5 14 72 to 79 155 - 170 16+
Forme Black Rocks HT 2 S 29 16.5 14 72 to 79 155 - 170 16+
Forme Black Rocks HT 1 M 29 17 14 77 to 83 168 - 180 16+
Forme Black Rocks HT 2 M 29 17 14 77 to 83 168 - 180 16+
Forme Curbar Pro 29 L 29 19 14.5 78 + 178 - 185 16+
Forme Black Rocks HT 1 L 29 19 14 83 + 178 - 190 16+
Forme Black Rocks HT 2 L 29 19 14 83 + 178 - 190 16+
Forme Curbar Pro 29 XL 29 21 14.5 85 + 185 - 193 16+

Frequently Asked Questions about MTB Sizes 

Here are some quick answers to popular questions around MTB sizing. 

How are mountain bikes sized? 

Mountain bike frames are sized in inches, with some models coming in Small, Medium, and Large. To find the right size for you, we advise using your inside leg measurement. You can use our table above as a guide, and our product pages also have sizing recommendations. 

How does the right mountain bike size enhance the overall riding experience, especially during long rides or challenging terrains?  

The right mountain bike size enhances comfort and control, crucial for long rides and challenging terrains. A proper fit reduces strain, boosts endurance, and improves handling, ensuring confidence and efficiency on trails.  

How do I measure my inside leg accurately for choosing the right mountain bike size?  

To measure your inside leg for the right mountain bike size, stand barefoot with your legs apart. Use a measuring tape to measure from the floor to your crotch, ensuring the tape is snug against your inner thigh. This measurement will help you select a bike with proper stand over clearance for a comfortable and safe fit. 

Child on cube mountain bike - Bike Club