Riding a mountain bike is a fun and thrilling way of exercising and enjoying a wide range of health benefits. This is not possible though when you have the wrong fitting on your mountain bike. A wrong size bike leads to stress injuries and loss of control among other effects. Paying attention to the size of the bike you are considering to purchase will ensure comfort in all of your rides.
In general, a right-sized mountain bike leaves about 2-3 finger spaces between the top tube and the inseam of your pants when you straddle your bike with both feet flat on the ground. You should also reach the handlebars without struggling and your feet should be comfortable while pedaling.
We have covered what you need to know to get the right size on your next mountain bike. For those who own a bike already, we’ll show you how to fix it if does not fit.
Why have the right size on your mountain bike?
• It enhances your comfort while riding
• Prevents strain injuries, pain and, numbness
• Enhances riding efficiency thus reducing fatigue
• Improves your bike’s overall performance
• Gives you better control over your mountain bike
Signs you have the wrong mountain bike size:
• You constantly suffer from back pain
• Your saddle is too high interfering with your comfort
• Your saddle is too low making it hard for you to ride
• Your new mountain bike has some changes in the stem
How to size your mountain bike
The size of your mountain bike can be determined using various methods. We have covered some methods below that you can use irrespective of the user’s age.
Measuring your inseam
This helps to determine the frame size you need.
• Take off your shoes and stand straight
• With your back against the wall, stretch your legs 6-inches apart
• Measure the distance from the floor to your crotch
• Your seat tube length will be the number you got above (in inches) multiplied by .67, subtract 4. Multiply by .65 for a C-C frame
Stand over test
This is a simple way of determining whether your bike is the right size for you.
• Straddle the bike with your leg over the bike’s top tube. Ensure your legs rest flat on the floor.
• The right size bike leaves space of about 2-inches between the top tube and your crotch
Find your ape index
This helps determine the right reach to the handlebars. It should be the selecting factor in case your height and inseam length put you in between two bike sizes.
• Measure the distance from your right fingertip to the left fingertip
• Subtract your height from the above measurement
• If the measurement is positive, it is known as a positive ape index and means you should select the next largest size
• The converse (negative ape index) means you should go for the smaller of the two sizes
Finding the perfect top tube length
• Measure the distance from your knuckles to your collarbone while standing upright with your back against the wall
• Measure from your crotch to the base of your neck (where you have a hollow)
• Add the two figures above and divide by 2
• Add 4 to the number above to get the ideal top tube length
Mountain bike size chart
A mountain bike height chart shows the general mountain bike sizes against the seat tube numbers. This is the easiest method of sizing a mountain bike.
If you already have a bike;
• Measure the distance from the top of the seat tube (where the seat clamp and post meet) to the middle of the axle that holds the crank arms together
• The above measurement is the seat tube length
• Check on the chart below to confirm the ideal bike size
Seat tube sizes Height Bike size
13-14 inches Between 5-feet to 5-feet 4-inch Extra small
14-16 inches 5-feet 4-inch to 5-feet 7-inch Small
16-18 inches 5-feet 7-inch to 5-feet 10-inch Medium
18-20 inches 5-feet 10-inch to 6-feet 1-inch Large
20-22 inches 6-feet 1-inch and above Extra large
How to determine the ideal mountain bike size using your body
This is how your body should feel when riding the mountain bike;
• Your elbow should be slightly bent and your shoulders should be relaxed
• Your heel should just touch the top of the lower pedal with your leg
• Ensure your knees bend slightly with the bottom of each pedal’s stroke
• Experiment moving the shifters and brake levers further in or tilting them
How to adjust your bike
You may want to make the necessary adjustments to your mountain bike if it does not fit. A small bike is easier to adjust than a large bike. A small fit requires changes as well as new bike parts. You can easily lengthen some parts on the bike to your desired level.
Adjusting the seat height
• Loosen the bolt that holds the seat post using a wrench
• Get the ideal length by placing the tape measure where the pedal crank and the bike attach
• Stretch the tape measure out to your inseam length measurement
• Swivel the seat post either up or down until you match the measurement above
• Tighten the seat post bolt using the wrench
• Ensure the saddle’s lowest point is even with the upper end of the tape measure
Adjusting the handlebars
• Loosen the bolt that attaches the handlebar to the mountain bike’s frame
• Lean forward and down to a comfortable position
• Raise or lower the handlebars to fit the comfortable position above
• Use a wrench to tighten the handlebars
Adjusting the seat tilt
• Tilt the saddle back and forth until you achieve a perfect fit. This is achieved when your pelvis is flat when seating on the saddle
• Ensure you do not slide either forward or backward while on the saddle
Be sure to make further adjustments if you do not feel comfortable after adjusting your bike. With a well-adjusted bike;
• Your will hips face straightforward when sitting on the bike with your shoes on
• The pedal with the lowest point during rotation will be close to the floor as possible
• Your heel rests on the pedal while your knee will be slightly bent when you place your foot on the lower pedal
Riding on a mountain bike with the perfect fit is satisfying. We believe this article will make it easier for you to get the right bike next time or even correct your current one. You can also use this guide to make your online purchase easy.