Mountain Bike Sizing Guide

Mountain Bikes are known for their off-road use in tough terrains. Generally, they come with 26″ wheels. However, recently they have launched 29″ and 27.5″ (650b) wheeled bikes. 

These new sizes give greater speeds and are usually better to cover bumps. MTB sizes are measured in inches or as S, M, and L frames.

What Size Bike Do You Need If You Are Between Sizes?

The bike sizing calculator can sometimes suggest two different sizing options. This ensures that both the suggested bigger and smaller measurements would be appropriate. 

The size to choose is a personal preference. However, most mountain bikers prefer a bigger model. If you don’t feel so cramped, you should attach a shorter stem (depending on the model) to boost a bigger bike’s performance without negatively influencing the handling. It is the reverse of a road cycle, where the backbone will be lengthened rather than being shortened.

How Are Mountain Bikes Sized?

Mountain bikes are usually measured in centimeters, or as low or medium in dimension. That is usually focused on the length of the seat tube. The measurement needs to be from the middle of the front chainring to the tip of the seat tube. 

Mountain bike models do not often adopt a traditional formula so that the calculation may be centered on a simulated seat tube calculation. Sizes differ significantly from one maker to another.

MTBs are measured from the bottom bracket core to the tip of the seat vent. MTB top tubes often slope down. They enter the seat tube in a lower position than road bikes to give a rider more standover height. 

So it is worth taking the calculation of the inside leg and matching it with the manufacturer’s standard. Always check the supplier’s dimensions, or visit a shop and speak to a knowledgeable staff member making the final decision.

Does Wheel Size Make a Difference?

There are mainly three prevalent wheel sizes on mountain bikes; 26″, 27.5″ and 29″. Although there are other sizes including 27.5+, ‘Mullet MTBs’ (27.5′′ rear & 29′′ front) are becoming more common. 

The size of the wheel you chose can affect the riding posture & riding style. Find below which wheel size is a better fit.

26” Wheels

This is the standard scale of the mountain bike wheel, but now the bulk of MTBs have more prominent spokes. Even 26” wheels are a decent choice for young riders and younger adults who consider them more accessible than more significant hurdles. Most dirt jumping MTBs continue to roll on 26″ wheels.

27.5” Wheels

It is also the most popular wheel size from road bikes to downhill steeds on all mountain bikes. 27.5” wheels have the perfect combination of nimble handling and fast-rolling efficiency. Many vendors sell 27.5” wheels on the wider frame sizes on narrower framed frames with 29″ wheels.

27.5”+ Wheels

These tyres have a broadly similar diameter to 29” wheels with 2.8″ and 3.0” tyres on a 27.5″ rim, and are often consistent with 29er MTBs that showcase boost axle spacing on the fork and back wheel. This wheel size is optimal for hardtails with more grip and more float (cushioning), although the excess weight will make them slower to accelerate.

Right Saddle Height

The correct height of the saddle plays a very significant function. If it’s too low, you’re not going to get enough power in your feet. In mountain-bike competitions, when the saddle slips one inch down from its usual position, you lose around 25-50 percent of your energy. 

Preventing to fix it can cost you your position and about 15 seconds, too, but then, that’s not that difficult to come up with the group with the correct saddle height and can even get to the next group all the way ahead. Also, the right height of the saddle plays a significant role.