Last Updated on September 11, 2021
Mountain biking is more fun if you ride a bike that’s your right size. This is why many cyclists ask what is the right mountain bike size for them.
Bike size is one of the most important decisions you need to make if you’re planning to buy one. It’s where your comfort, confidence, and skills stem from.
A bike that fits you correctly is great to ride because it lets you tackle different terrain without doing awkward positions and movements. It also helps you improve bike control and be faster on your ride.
A bike that’s too small isn’t very stable and can throw you off your bike when you hit downhill trails. Meanwhile, bikes that are large for your size are heavier and feel very bulky that you can’t properly move with them.
So, how to choose the right mountain bike size? And what are the things to consider to ensure the right bike fit? Read on to know all of these.
What mountain bike size do I need?
Every bike feels and rides differently because they have their own geometry, design, and measurement.
The seat post tube is the vertical tube that supports the saddle. Meanwhile, the top tube is the horizontal tube found at the top-most part of your bike.
There are also many ways to know the right bike size. But one of the most common methods is to measure the seat tube and top tube length from a bike chart.
Bike manufacturers also have different chart sizing options for their bikes just like clothes. The usual bike size chart guide usually comes in these size options:
- Extra small (XS)
- Small (S)
- Medium (M)
- Extra-large (XL)
This makes it easier for riders to choose the right bike size for them. Extra small and small bikes are usually for cyclists who are 5-feet below to 5’3 in height.
Meanwhile, medium bikes are for riders who are 5’4 to 5’6 in height. Large and extra-large bikes are then for bigger and taller cyclists who are around 5’7 to 6-feet and above in height.
This means that the top tube length, wheelbase, and seat tube length increase as the bike becomes bigger.
Bikes with short seat tubes mean shorter people can still fit even if it has a longer reach because they can easily adjust the seat height. But it’s still best to ensure that the top tube and seat tube lengths are the right bike fit for you when choosing a bike.
Seat tube length dictates the lowest saddle height you can set up. Meanwhile, the top tube length dictates how far you’re going to stretch your arms when riding the bike. It’s best to choose a bike from a brand that offers its own size chart so you’ll get an accurate measurement.
Below are some of the most common mountain bike terms used for sizing found in a bike size chart.
Mountain Bike Geometry Terms for Sizing
Top tube length
The top tube length is the length between the upper portion of the bike’s head-tube to the center-most part of the seat post. The longer the top length is, the more you stretch out your hand. Cyclists with a long upper bodywork are great on bikes with long top tube lengths.
The stack height is the distance between your bike’s center area of your head tube and the center portion of your bottom bracket.
This is where the minimum and maximum height of your handlebars depend on. It also dictates your bike’s reach. The higher the stack height is, the more elevated your ride becomes.
Seat tube length
The seat tube length is the distance from the center area of your bottom bracket to the top-most part of the seat tube.
This determines how low or high you can adjust your bike saddle. It’s also where the length of the rider’s legs depends on. The longer your legs are, the better it is for you to have a biker that has a long seat tube length.
Down tube length
The down tube length is the distance from the bottom-most part of the head tube and the center area of your bottom bracket.
This isn’t always listed on a manufacturer’s size chart guide. But it’s not that difficult to measure. Simply measure the vertical tube from your saddle. This is also where your height depends.
Bottom bracket height
The bottom bracket height is all about ground clearance. The higher the bottom bracket height is, the less likely it is for you to accidentally hit big rocks with your bottom frame. It is the distance between your bottom bracket’s center area and the ground.
Downhill bikes usually have a lower bottom bracket height compared to cross-country bikes. It’s because lower BB height provides better stability. After all, the center of gravity is low. On the other hand, higher BB height is easier for climbing because the geometry is elevated.
A mountain bike size chart guide also has the wheelbase. A bike’s wheelbase is the horizontal measurement from your rear axle to the front axle. You have a more stable bike if you have a long wheelbase. But it usually feels a bit draggy and heavier. Nonetheless, it’s still a good idea because it doesn’t easily rattle on rocky trails.
The reach is the length from your top head tube and bottom bracket. It indicates how roomy your bike feels.
The chainstay length is the frame size chart guide measurement from your bottom bracket’s center to the rear axle. A bike with a short chainstay is more poppy and playful than those with a longer measurement.
Things to Consider to Choose the Right Bike Size
The first item to consider to choose the right bike size is the bike type. This means that you need to know what bike you’re getting.
Here are the main bike types to choose before you look at bike size charts:
Cross-country bikes have similarities with road bikes because they are made for uphills and long rides. They’re not very aggressive as they have short-travel forks and shocks. They are also lighter and usually made from full carbon components just like road bikes.
Trail bikes are more aggressive than cross-country bikes. They have medium-travel suspension and can handle uphills and downhills decently. Meanwhile, enduro and downhill bikes are more on the extreme side of cycling.
Enduro bikes are basically trail bikes that have long-travel suspension systems. They’re also heavier and bulkier. Downhill bikes are the heaviest kind of bike where you need lots of stability and durability. They have oversized dual crown forks and shocks with 200 mm of travel.
Knowing the rider’s height lets you know if the frame is going to be short or long. Know the height from the bike frame size chart so you won’t feel awkward when riding your bike. A bike that’s too tall for your height compromises control and maneuverability. Meanwhile, a short bike feels too shaky and unreliable on high-speed sections. However, the latter is ideal for a city bike.
Know your riding style. If you’re the kind of mountain biker who wants to have fun on trails, then you should get a smaller bike. This lets you do fun tricks on your bikes, such as doing jumps, whips, and wheelies.
However, this compromises speed and stability in high-speed sections because of the shorter wheelbase. On the other hand, bigger bikes are better if you are into racing or if you’re not fond of doing skids and hitting berms. You can also use a bike size calculator to know your right bike fitting.
Choose between 27.5-inch bikes or 29ers. Most modern and high-end bikes already have a 29-inch wheel size, which is also called wheel diameter.
These roll faster, are more capable of traversing over huge rocks and stumps, and are designed for racing. But there are still bike brands that manufacture 27.5-inch bikes which are ideal if you’re into joy rides or dirt jumps.
Dropper length comes in different ready-made options in their own chart. The usual choices are:
- 100 mm
- 125 mm
- 150 mm
- 175 mm
The aforementioned measurements are the travel options of droppers. 100 mm droppers aren’t any more common these days.
Meanwhile, 125 mm droppers are ideal if you aren’t very tall or if you aren’t that comfortable in riding with a high saddle.
150 mm are the most common these days because they provide the most amount of versatility. 175 mm droppers are made for taller and larger riders who have large and XL-sized bikes.
Most cranks today come in 165 mm, 170 mm, and 175 mm cranks. 165 mm cranks are for downhill bikes because they are less likely to get pedal strikes because of their short length. 170 mm cranks are for trail and enduro bikes because they offer to pedal efficiency and safety from pedal strikes. Meanwhile, 175 mm cranks are for cross-country bikes because they are easier to pedal. SRAM’s GX Eagle and X01 Eagle lineup offer some of the best cranks in the market.
Benefits of Getting the Right Mountain Bike Size
Good bike position results in relaxed shoulders and slightly bent elbows
One of the best benefits you can get from having the right mountain bike frame size is that your shoulders and arms feel more comfortable. They should be slightly bent and your shoulders wouldn’t accumulate too much pressure.
Having the right saddle height and position provides you with better balance and control. It also helps you pedal better on rocky trails.
Having your knees slightly bent at the bottom-most part of every pedal stroke makes long rides and pedaling more comfortable. Getting the right size also improves pedaling performance efficiency.
Choosing the right bike frame ensures that you gain the utmost maneuverability and control. It also makes sure that you don’t feel awkward on your bike.
Shifters and brake levers
Adjusting the position of your brake levers and shifters gives you maximum comfort and control when descending. You don’t anymore have to hyperextend your fingers or hands just to reach them. This then lets you gain better control and maneuverability because you can properly hold your grips. You can ask for advice from experts in your nearest bike shop if you are unsure of your adjustments and to know the reason for possible discomfort issues you might have when riding a bike.
What about women-specific mountain bikes?
Women have different body dimensions compared to men. Examples of these are their height, reach, and height. There are even bike models that have been specifically altered to provide a better bike fit for women based on rider feedback and body geometry data analyses.
But it’s worth noting that there’s not much difference from a men’s or unisex bike compared to the women-specific bike equivalent. Most of the time, they’re just small adjustments in the geometry as well as more feminine colorways.
Some bikes have thinner grips, lighter forks and shocks, and narrower bars.
Choosing the right mountain bike size is important if you want to make the most out of the trails. These give you better handling, control, and maneuverability in the trails. Getting the right bike fit also lets you go faster without compromising comfort and safety.
It might sometimes seem too much to go on very specific numbers especially if you’re still new. But it’s totally worth it once you get the right measurements. You don’t just get any bike you think looks nice and cool while putting in the components you like.
You first need to look at the size and make sure it’s the right frame size for your height and body build. This lets you enjoy your mountain bike even more, so you won’t feel awkward about riding it.
It also makes you a better mountain biker because you now know how to play with your bike and make it a part of your body.