New and experienced mountain bike riders are attracted to the unpredictable terrain, physical endurance and stunning views that are readily available on a ride. What’s not to love about hitting the road and taking on a challenging climb? Of course, these incredible experiences are only possible if you are paired with the right bike that is the right size for your frame and specific build, as anything else is going to hold you back from your peak performance. Today we are going to look at how to navigate sizing guides for mountain bikes, and what factors you need to take into account for your final decision.

FRAME SIZE – 13-14in – 14-16in – 16-18in
RIDER HEIGHT – 152-162cm – 162-170cm – 170-178cm

Above is a standard mountain bike sizing guide that will be used by most mountain bike manufacturers. Although it is always recommended that you request the size guide directly from the manufacturer you intend to buy from just in case. You also want to consider international sizing guides and how they differ, as you might be tossing up between an Australian-made and Italian-made bike and those inches always add up. Retailers, such as Decathlon, will almost always show the size guide on every model of a mountain bike. Overall, though, it is unlikely that they will be too dissimilar – but be wary of manufacturers working to different specifications. Now, let’s understand what variables are important to think about.

Are you still growing?


Adolescents who are looking for a mountain bike will need to be cautious of spending too much on a new frame if they are likely to soon grow out of it, this will not only be expensive but you run the risk of harming your body if you ride a mountain bike that is not appropriate for your size. If this is the case, try and find a mountain bike that can be taken apart and fitted with new parts to accommodate your new needs should this be the case.

Serious cyclers will often by separate parts and essentially build a bike that is unique to their size and preferences. If you think that you are only just fitting into a bike size, it might be worth taking the next size up for a test ride on the bike to see if that is going to be a better outcome on your ride.

Ask around

A great thing about being a cyclist is that you have a built-in community which gives you the opportunity to meet riders and hear about their preference in mountain bikes and what size works best for their style. They might even point out features that you hadn’t thought to include in your size assessment. If you have some riding peers who are about the same height as you, ask to take their bike for a lap so you can get a feel for that particular size. You also want to be asking bike store workers what they ride, as they typically gravitate to the better models on the market given their knowledge and expertise.

There are also many forums and local groups that cyclers belong to, and plugging into these networks will give you access to a number of experts and the opportunity to ask questions that yield real and honest answers. See if there are any Facebook Groups you can join to see what people are riding and how they make an informed decision on the sizing.

Buying new makes a difference


It might be tempting to secure a quality mountain bike second hand, but you should only do this if you are very certain of the size you need and know how to measure up a bike. Otherwise, you run the risk of buying a bike that has been modified by the rider and no longer a true size to rely on. When you buy new, the bike is exactly to the standard specifications for you to enjoy or modify as you see fit and can be more straightforward than assessing a modified bike.

You also don’t get the same warranties and assurances when you purchase second hand, which can be a problem if you find you have chosen the wrong size and realise after the fact. If you are still interested in seeing what used bikes are out there, always insist on a test ride and inspection so you can assess function but also understand the sizing.

Riding frequency

How often you intend on riding your mountain bike may influence the size you choose. If you are a seasonal rider who competes in global bike races but doesn’t ride much outside of those events, then you might choose a bike that is going to impact your performance, which can often be a smaller bike frame if riders are expecting to be climbing for large stretches of the ride. It is not uncommon to see riders have an everyday mountain bike and a competing mountain bike, so assess what this new bike is to be used for before you make the selection.

Consider hiring first


Don’t feel like you can make the decision with the information available to you? It might be a great idea to actually hire a number of bikes one after the other so you can see how they handle different terrains and for varied distances. When you choose your mountain bike you want to be 100% sure that it will deliver to your needs, and hiring will give you an opportunity to try before you buy. When you do hire the bike model you want to buy, also pay attention to how your body feels post-ride as this can signal whether or not the size is a perfect fit or has you cramping and hunching. Muscle fatigue is part of the cycling experience, but back pain and stiffness should be explored as it could be a sign of an incorrectly sized bike.


If you are serious about riding then this will likely not be the only bike that you ever buy, but you need to understand your size before you can build your collection. Don’t be afraid to visit the bike stores a few times before you make your final decision and be transparent about your purpose for the bike, riding style and any other factors that are going to influence your performance.