Choosing the appropriate mountain bike size is as important as getting the right kind for you. You can’t just grab a nice looking carbon trail without considering its measurements, and everything will be fine and dandy. Ultimately, it has to fit – one that will be a joy to ride.
A bike that’s too small or too large will bring about uncomfortable handling (and more back problems) in the long run. Here’s a word of advice: before you buy that bike you’ve been eyeing on, read this article first to ensure you are making the right purchase. And in doing so, you will achieve maximum riding performance while reducing your risks of injury.
| Your Height | Suggested MTB Frame Size | |||
|---|---|---|---|---|
| Feet & Inches | Centimetres | Frame Size (inches) | Frame Size (cm) | Frame Size |
| 4’10” / 5’2″ | 148cm / 158cm | 13″ / 14″ | 33 / 37 | X-Small |
| 5’2″ / 5’6″ | 158cm / 168cm | 15″ / 16″ | 38 / 42 | Small |
| 5’6″ / 5′ 10″ | 168cm / 178cm | 17″ / 18″ | 43 / 47 | Medium |
| 5’10” / 6’1″ | 178cm / 185cm | 19″ / 20″ | 48 / 52 | Large |
| 6’1″ / 6’4″ | 185cm / 193cm | 21″ / 22″ | 53 / 57 | X-Large Bikes |
| 6’4″ / 6’6″ | 193cm / 198cm | 23″ / 24″ | 58 / 61 | XX-Large |
There’s a lot more to it than just this table, but it gives a general direction. Some riders have longer legs compared to others which can mean you need a different frame. Best way to figure out the perfect fit is to visit your local bike shop.
Contents
What is Your Bike Standover Height?
You may think that a medium-size MTB for an average built person like you is all there is to it. You need to familiarize yourself with your bike dimensions before you can consider that a certain bike is your right fit. One is the standover height – this is the vertical length of the top tube of your bike to the ground, much like its inseam. It should ideally be lower compared to your inside leg measurement. You’ll know why.
Often you read about bike listings that indicate a value in inches, you might wonder what the heck it means. Usually, this number is the distance between the axle on the bottom bracket and the top seat tube that supposedly represents the standover height. This is not a universal standard, though because other bikes use different points for measuring. No matter how it is defined, the standover height presented to you still does not determine whether there’s enough room for the rider to straddle or not.
Bikes may have their own design for their top tubes. What you will need is the standover height to ensure that there’s enough space between your crotch and the top tube. You have to factor in how you ride your bike as well. A clearance of a few centimeters is enough for cross country bikers while those who perform dirt jumping would require more.
As mentioned, many bikes can provide this figure on their specs, but it is still best to measure it by standing over the frame yourself. Straddle your legs on the top tube and plant your feet firmly on the ground. Then raise your bike to your maximum crotch gap. This distance should be about two inches, which is good enough for conventional riding.
For the dirt jumper who often bends his knees during his stunt, a clearance of more than five inches is recommended. To test the fit, he should ride the bike gradually from the start then make quick jumps. He should land with bent knees that are straightened up as he recovers.
This should be done repeatedly not just on the current bike he is looking at, but for all MTBs that are on his buying shortlist in order to get a good approximation of the crotch distance he prefers. Two bikes may have the same frame dimensions, but the might also have a totally different standover height from one another.
Bike manufacturers have their own way of tagging the sizes using different factors such as the top tube designs. While they usually base the size of the bike frame on the distance between the middle part of the bottom bracket and the top portion of the seat tube, its top tube may be more curved than the other. It could also have different height of its bottom bracket. Some would even measure it using either its highest part, or its center.
Essentially, the bike standover height is dependent on the top tube design and the height of its bottom bracket regardless of the frame size. The area where you measure it is considered in the equation. For top tubes that slant upwards, it should be about 2 inches from the seat post.
Meanwhile, suspension forks have an impact themselves in terms of the travel levels that each mountain bike has. The shorter the suspension fork travel is, the lower its front end would be. For example, an MTB with a 100mm fork travel will cause the front end to waver more than a 125mm suspension fork. Rigid forks will also entail a low front end given the ascending and descending motion of the bike front wheel.
By design, bikes with full suspension are the tallest. This is because their pedals are positioned higher from the ground. These, along with the bottom bracket ensure that they allow the bike to get through road bumps and distractions, with the compression a full suspension type is capable of.
Even the wheel size influences the standover height. Roughly speaking, the smaller the wheel size, the lower its front end is. That said, a 29-inch wheel front end will be higher than that of the 26-inch wheel. This is considering that their suspension fork travel is similar.
Also with the same bike frame size, you may get a different standover height if the wheel size differs. If you can’t find a bike that allows the minimum of 2-inch crotch gap, look at getting smaller wheels. Because really, the standover height may still vary no matter if the two bikes in comparison have the same brand or not.
There is no cookie cutter for measuring bikes because many aspects affect the standover height and frame size, among others. So checking this out yourself should give you a more accurate figure.
What is the Distance to Your Bike Handlebar?
When you ride your bike, have a feel on your handlebars – are they comfy and easily reachable even with only a slight elbow bend? And while you’re at it, check if your knees hit the handlebar whether you’re heading straight or turning left and right. You should test this while pedaling with the balls of both your feet, and not with your heels.
Your knees should not only be touching the handlebars when you ride your bike, they should not also collide with your elbows. See if you can press the brake lever with ease. In any case, you can make adjustments on your handlebar stem as necessary.
You can sit upright with most modern mountain bike designs unlike the older ones with a 10-speed handlebar, which you have to hunch over on. This old version provides utter discomfort, reduced visibility, and less control during sudden braking.
Nowadays, the handlebar should be about the same level as your seat, if not slightly above it to allow upright sitting position. When it’s too low, you’re putting a lot of stress on your arms and wrists, not to mention your neck and spine. If this is the case, you can adjust the handlebar stem to raise them a bit to a more comfortable level.
Keep in mind that the adjustability of your stem is limited. If you need to do a much higher adjustment, your brake and shifter cables may not have enough slack to lift your handlebar stem. As such, you will probably have to get new cables or have them done at a bike shop. If this is not possible, you might even have to change your handlebar stem altogether.
Perhaps you can switch to larger wheels to address your handlebar issues. The 29ers will both have more suspension fork length and raised handlebars, unlike a mountain bike with only a 26-inch set of wheels. If you have a short height, using a smaller wheel size can help go you a nice bike fit.
Do You Have a Toe Overlap Situation?
Toe overlap is when your toe grazes your front tire after making a sharp turn from a very slow speed, i.e. doing a U-turn on a narrow road. Some bikers have implied that the toe overlap does not happen in high-quality bikes and is a design flaw. Actually, a toe overlap results from different design factors, and often cannot be avoided with smaller bike frames.
To check if your bike has this, do a test ride. When your pedals are aligned horizontally, turn your handlebar either to the left or to the right, and notice if your toe passes the front wheel.
Generally, a toe overlap is not a huge issue because when you corner at regular speeds, your bike front wheel will not make any sharp turn for your toes to hit them. Otherwise, this would mean a disaster. However, this is not ideal with slow riding, especially with rough terrain which can cause your front wheel to make right and left turns more frequently, hitting your toe in the process.
What are Your Vital Statistics?
No, I am not talking about your hip-waist ratio, silly. I am referring to certain body measurements that are considered vital in determining your corresponding bike frame size. These include your inseam length, arm length, body length and torso length.
To get the length of your inseam is pretty much the same with the inseam of your favorite pair of jeans. In fact, you can use this same value as well. But for purposes of explanation, you need to measure the distance of your crotch to the floor while standing barefoot. As an alternative, you can also stick a book in between your crotch, and mark its corresponding height on a blank wall. You will get the inseam by measuring its length from the floor.
You might need a helping hand when getting your arm length. Find the edge of your collarbone, which is above the tip of your shoulder, and we will call it point A. Point B will be your wrist bone on your pinkie side. With your arm extended at about 45 degrees from your side body, get the measurement between the two points and you will have your arm length.
Body length is the distance between your collarbone midpoint, which is the indentation below the Adam’s apple, and the floor while standing straight. This includes your torso. Using a tape measure, start off from the collarbone and step on the tape measure where it touches the floor. Where your foot rests on the tape measure is your body length.
You can also do the measurement using the wall once again as a marker by placing the edge of your pen on your collarbone indentation while pointing the pen tip on the wall. You will get your body length by measuring from the marked spot on the wall to the ground.
For the length of your torso, simply subtract the value of your inseam from your body length. Please note to get all your dimensions in either centimeters or inches.
Frame Size
After jotting down your body measurements, deduct any amount from 36cm up to 42cm from the inseam value in centimeters. The computed value corresponds to the length of the top tube down to the bottom bracket. If you prefer taking the estimated value between the mid points, just deduct about 2cm from your inseam length.
Tip: if you’re taller in height, use the higher value of up to 42cm, otherwise, use a lower number.
Don’t go lower than the minimum of 36 centimeters either to acquire the length you need for your seat tube. This is because you would want to stay within the 2-inch gap between your crotch and the top tube.
As mentioned earlier, bottom brackets are much higher with bikes with full suspension. They also have a low standover height as a result. This makes the length of your seat tube shorter given the higher suspension fork travel of your bike.
On the other hand, standover height is not a problem for step through bikes which either have a very low or non-existent top tube. This type of bike is great for commuting and cruising.
Top Tube
The length of the top tube is the horizontal distance between one end that meets the head tube, and the other that aligns with the seat tube. As such, it is an imaginary line, but is worth noting because many bikes are being designed with sloped top tubes.
You can get the length of your top tube by starting with combining your torso and arm lengths. Then multiply the resulting number anywhere from 0.47 to 0.50. Casual riders should use 0.47 while 0.50 is for the aggressive ones. In between, you can use 0.48 to 0.49 to get the top tube measurement.
Your top tube must never be measured in terms of its actual length, that is, from top to bottom. This is because your body is positioned horizontally on top of it to reach the handlebar. As such, this is the part that is relevant to the rider.
Handlebar Stem
The length of your stem changes your reach to the handlebar. Using the center points of your steering bore and handlebar clamp, measure the imaginary line in between to get your stem length.
In reference to your body measurements, your combined arm and torso lengths multiplied by 0.085 for average riders will arrive at your stem length. Aggressive bikers should use a multiplier of 0.115 for their computation. Remember to just use this value as a guide because the best way to know for sure still is to test sitting on the actual bike.
Crank Arm Length
Bikes commonly have 170mm to 175mm cranks, but they can be as short as 140mm or as long as 190mm. They are directly proportional to the height of the rider, the taller he is, the longer his crank length should be. This is just a guide however, and not a guaranteed formula, because other factors must be taken into consideration such as your pedaling style.
The length of the crank arm can be determined by measuring the distance between the center points of your bottom axle and pedal axle. If your bike has the appropriate measurement, it will enhance comfort with your bike ride.
Saddle Height
Finding the appropriate saddle can be tricky because it is crucial to determine the curvature, shape and height that works for you. Ultimately, your saddle should be positioned properly to achieve an optimal riding performance. To get the right height, you must be able to rest your heel on the pedal with a straight knee in a 6 o’clock position.
Using either a stationary or moving bike, you should pedal to the point of reaching its lowest part with your heel. You need to adjust its height when you find that your knee still bends with the given pedal position.
Multiply your inseam length by 1.09 to get your saddle height computation. This multiplier value is derived from the distance of the saddle top where your sit bones lie, to the central point of your pedal spindle. You can use the figure as your reference for adjusting the saddle height.
Either you get the fit by manually adjusting it or using the computation, both should be able to provide you with a good saddle match. In the meantime, dropper posts are an option for advanced riders. These enable them to pedal up the hill with better power transfer on a higher seat. And before they hit downhill, the rider can drop his seat out of the way for a smooth landing.
Saddle Setback
The saddle setback for bikes pertains to the horizontal distance between the front portion of the saddle and midpoint across the bottom bracket. You know when you have the right saddle setback when you are well balanced, and don’t require much effort to support your weight.
Just like you did getting your saddle height, only this time you should move the saddle itself either forward or backward so that your knee is aligned to the pedal spindle. At this point, your crank has the 3 o’clock position.
With some help, ask a friend to measure how far the line is from the nose of the saddle to the bottom bracket with a plumb line or a tape measure. You can also use the area below your knee cap as starting point. The other end touches the crank arm which corresponds to the rotation of your knee and the pedal.
A saddle that sits with your knee cap aligned to 2 centimeters from the end of the crank arm will promote effortless pedal action. This, in turn, increases your pedaling by the minute. With your knees located at 2 centimeters further, you will achieve more power with uphill climbing even when you are seated.
For rides requiring steeper climbs, your saddle should be pushed more forward as this helps in maintaining contact between the ground and the front wheel. This is matched by a foot position that has the balls of your feet on the pedal spindle, if not about 2 centimeters further from it.
Adjust your cleats depending on the size of your feet. If you have large ones, your cleats have to be placed further behind and at the same time, holding the balls of your feet on the spindle. The opposite should be done for those will smaller feet, with which the cleats should take a more forward position.
Handlebar Height
You can measure the height of your handlebars by their distance from the ground. Saddle height must be included in the equation as well. When you subtract it from the handlebar height, the resulting value should be appropriate for your handling and riding style.
Tall riders prefer a saddle that is higher than the handlebars by about ten centimeters while the opposite goes for the shorter individuals. But this is not the only factor that influences your ideal handlebar height. As mentioned, the way you ride your bike should be considered.
For example, with slalom and downhill riding, raised handlebars are preferred for climbing. This may mean higher wind resistance, but the higher your handlebar is, the better control you will have with your bike especially going downhill.
Mountain bike newbies, on the other hand, may start off with lower saddles and adjust them as they progress with their ride.
Handlebar Reach
In simpler terms, handlebar reach is the length between the handlebar and saddle. One way to gauge this is by sitting on the saddle while holding on to the handlebars and pedal to a horizontal crank position. Can you or your friend see where the handlebars fall in relation to your axle? If they are far ahead, you will be too stretched out, making for an uncomfortable ride, unless you are the advanced type. When it comes down to which one is the right reach is really a matter of personal preference, although your elbow should be up to 4 centimeters forward from your knee.
Bar Ends
Bar ends are stubby accessories and are exactly described as they are named- they are placed on the ends of the handlebars. While these are optional, bikers normally use them as climbing aid and provide them with better leverage.
Average riders work with bar ends placed on a 45-degree angle, it becomes narrower with competitive riders who do mostly uphill maneuvers. A 15-degree angle provides higher pulling capacity for the biker while standing on the pedals.
Last word
Now that you have learned how to determine the appropriate sizing of bike components relative to your body measurements, you can use this knowledge to guide your bike purchase. You will then be able to decide with much more confidence if the bike has the right fit for you or not. Happy shopping!
I always had a thing for cycling sports and love almost anything that involves bikes and boards. I work part-time as a designer in the tech industry and work on my blogs whenever I can.