Mountain bike sizing has always been related to the ergonomic aspect of riding. That’s why mountain bikes are produced with different geometries to fit every single rider.
It’s a common problem for novice riders to choose a wrong geometry for their body type, simply because they don’t know any better. Here I will try to explain and the ergonomics of the bike and how different geometries would affect the riding performance.
Note: There are different types of mountain bikes. Each riding discipline requires different geometries; The most common type is cross-country bikes, which is, for the most part, a bit more recreational, unless you take it to competitive levels. This article is mainly about cross-country mountain bike sizing.
Although personal preference can also be a factor, the bike geometry should mainly be affected by the rider’s height, and so the following mountain bike sizing chart is based on this factor. I’ll explain later on how else you can still personalize your bicycle accordingly if you already have one.
Mountain Bike Sizing Chart
Note: for “Frame Size” refer to the picture above
|Rider Height (CM)||MTB (CM)||MTB (Inch)||Saddle Height (CM)|
Note: Kids below 100cm should ride a 16-inch bike, from 100cm to 150cm they should ride a 20-inch bike, and from 150cm they should ride a 26-inch bike.
Other Factors to Considers
Cross-country mountain bikes usually come with a standard geometry in their wheelbase, chainstay, and bottom bracket height. However, some dimensions may vary:
For a wheelbase, you want a medium length. You want the bike to take turns at medium speed while not losing control over the bike. You don't want to feel like you are riding a very long bike, that while riding at a slow speed could be difficult to handle in turns, especially in rough terrains.
Bottom Bracket Height
You want the bottom bracket to stay low, so your center of gravity remains as low as possible without sacrificing clearance on the terrain. You don't want your pedals to be too close to the ground, either.
Saddle height is almost always dependant on the personal rider preference because there's nothing more important than how comfortable you feel while riding.
Stem Height and Angle
If you are tall, you should be looking for a longer stem, but not necessarily a higher angle, because that's related to how you feel on the bike according to the bars placement and the bottom bracket placement. Since most cross-country and road bikes are roughly the same geometry, then you shouldn't be changing that much.
Ideally, the higher the bottom bracket is placed, the higher stem you are looking for. That way, you are not crouched on the bike - giving you an uncomfortable posture while riding.
Other MTB Types
This mountain bike sizing chart mainly applies for cross-country bikes. Other disciplines of mountain bikes like downhill, free-ride, dirt-jump, bike trails, BMX, etc. have their unique geometries.
Downhill and Freeride Bikes
Downhill, for example, have raised bottom bracket, to allow a good clearance from the terrain.
They do not require a long and tall stem, because the front forks make the bike so tall it doesn't need a high angle stem.
Free-ride could be included in downhill since the geometry is roughly the same. The only difference between the two is that downhill is competitive, and the lines should be a lot more fluid, while in Free-ride, the lines can get slow, and you aren't necessarily competing against anyone.
Bboth bikes have a long wheelbase since you are taking corners relatively fast and you want to stay stable while doing that, avoiding tipping to the front.
Dirt Jump Bikes
Dirt jump bikes have a shorter wheelbase, lower bottom brackets and short, low stem, since you want the bike to be very maneuverable on the air, yes that's quite a dangerous sport if you ask me.
Trials bikes are unique on their species; they have a long wheelbase, high bottom brackets, and long high stems. You are looking for clearance, while at the same time being able to have lots of balance and comfort for those complicated techniques that get you through obstacles.
Last Word on Mountain Bike Sizing
That pretty much sums up all the mountain bikes, so let's recap:
- Bottom bracket, stem length, and wheelbase affect how you feel on the bike.
- The frame size is relative to the rider's height, regardless if it's a man or woman.
- The bike can be tweaked to accommodate to the rider's body type.
- It all comes down to how good the rider feels on the bike while riding.
Where to Find Mountain Bikes for Sale Online?
If you are interested in finding mountain bikes for sale online, you can always buy them on each maker's website. In addition there is always an option to buy bicycles online in one of these trusted online stores: