Can I Put A BMX Crank On A Mountain Bike? (Must Know This)
A crank is one essential part of every bike’s drivetrain. However, it’s natural to want to use a crank from a particular bike to a different one because of their striking similarities.
On the other hand, it’s ideal to know the compatibility of changing two different bikes before swapping the crankset. Hence, can you put a BMX crank on a mountain bike?
Yes, you can put a BMX crank on a mountain bike. But the BMX bottom bearing should be compatible with the shell of a mountain bike frame (a euro bottom bearing is best). Also, the inner diameter of the bottom bearing must match that of the spindle of the mountain bike (BMX is mostly 19mm or 22mm).
In this article, I’ll explain what you should know about putting a BMX crank on a mountain bike.
Also, this read will enlighten you about crank swapping and what crank will fit your mountain bike. In the end, you will know what size crank to buy. So without further ado, let’s go.
Can You Put a BMX Crank on a Mountain Bike?
You can put a BMX crank on a mountain bike (MTB), but this depends on two main factors. These factors will include
- The bottom bracket (bb) of your BMX.
- The spindle.
Before you decide to fix a crank from a BMX bike, know the bottom bracket your mountain bike uses.
However, the best bb to use on an MTB is the euro bb, just like the 19mm ODYSSEY euro-bb from Amazon.
Also, the BMX bb must be compatible with the bb shell of the MTB frame. And the inner diameter of the spindle should also fit the diameter; of a 19mm or 22mm spindle.
Before I go further, it’s ideal you understand why the spindle and bottom bracket are necessary for the swapping.
Firstly, the spindle connects the bb to the crankset, and these spindle diameters are from 19mm up to 30mm. Contrarily, the bb is what connects the crankset to the bike frame.
Equally important, the chain line must be the same to replace a mountain bike crank with that of a BMX.
Also, when putting the BMX crank on an MTB, the axle length will be a problem. Sometimes, a different model or crank type will require a particular axle length to fit a chain line.
Although all cranks serve the same purpose, they come in different types/forms too. Hence, changing a particular bike’s crankset is strictly model dependent.
Since it’s possible to put a BMX crank on MTB, is it worth considering, and what are the advantages? Below are two reasons why you should use a BMX crank on MTB.
#1. BMX Cranks are Strong and Durable
Although cranks are to be strong and last the taste of time, their durability sometimes varies. A BMX crank is one the most durable types there is.
These cranks have a lifetime warranty from the manufacturers. BMX is an extreme sports bike, so the crank and other components should be durable and strong.
Most BMX cranks are made from 4130-cromo, a strong alloy of chromium and steel. Cromo-made bikes are ideal for rough riders such as mountain bikers or BMXers.
#2. BMX Cranks Have More Length Variations
BMX cranks have various lengths from 170mm – 175mm, which is suitable for most riders. And the mountain bike usually comes in a standard length of 175mm.
So, modifying your mountain bike to your taste is possible and worth it. But first, you have to ensure the BMX bottom bearing is compatible. And use the right spindle.
Lastly, the answer to this technical question should end with a good BMX crank recommendation.
A good BMX brand is the 22mm ODYSSEY crank arms from Amazon at $179.
Are Pedal Cranks Generally Universal?
No, pedal cranks are not generally universal, or in other words, not typically interchangeable. Instead, the pedal cranks of a bike vary the same way various bike designs do.
For instance, the pedal cranks will either have a square shape mount or a diamond shape, etc. And the crank arms have different lengths you can see on the crank arm.
Also, the pedal size differs with the size of the cranks; the particular thread size will vary due to the crank.
And there are different types of crankset sizes which are;
- Single chainring cranksets.
- Double chainring crankset.
- Triple chainring crankset
How Do I Know If Cranks Will Fit My Mountain Bike?
To know if a crank will fit your Mountain bike, you should ensure that;
- The chainring of your mountain bike fits the cranks you intend to use.
- You get the right spindle length.
- The bottom bracket shell fits the new bottom bracket.
A crank spindle usually comes in two dimensions, which are 24mm or 30mm in diameter.
So if the crank spindle is 24mm, the chainring length should be 137mm, and 136mm for a 30mm diameter spindle.
Also, when searching for the best crank for your bike, you should know the crank material. Therefore, these cranks can come from three different materials, namely;
- Aluminum
- Carbon Fiber
- Steel
However, the bike type will determine what material of crank is suitable. Some materials can either be weak or too strong for what your bike activity involves.
Hence, you’ll find Aluminum cranks in MTBs and low/medium range bikes; and carbon fiber for all bike types. And steel for old model bikes. However, carbon fiber is more durable and strong.
Another essential aspect to consider when looking for a crank that will fit your mountain bike is the crank length. The crank length of a mountain bike should range from 170-175 mm.
Equally important, only replace a crank with a similar length because using a longer crank will affect your paddling. However, mountain bike cranks are shorter than that of a BMX.
A short-length crank helps to reduce any health risks you may encounter when paddling. Short cranks put no or less stress on your muscles or joints and eliminate chances of pain.
In other words, short cranks enable better and safer paddling action, allowing you to ride longer.
How Do I Know What Size Crankset to Buy?
To know the size of the crankset to buy for your bike, it’ll depend on certain factors, namely;
- The rider’s height.
- Bike type.
- Bike activities.
#1. The Rider’s Height
Using the rider’s height is an essential and standard factor when choosing the right crankset size. And this height refers to how long the rider’s legs are.
A measurement of 160-180 mm is the range of crank sizes available to choose from. This size measurement is the distance from the center of the pedal axle to the bottom bracket axle.
Also, road bikes usually have a standard crank length of 165mm, and a BMX crank will be 170mm. And for mountain bikes, a crank length of 175mm is common.
Nevertheless, below is a table with different heights and the length crankset that fits.
| Heights of riders. (feet) | Suitable crank length. (mm) |
|---|---|
| Under 4’11.8 | 165 |
| 5’2 – 5’8.5 | 170 |
| 5’8 – 6’0 | 172.5 |
| 6’0 – 6’6 | 175 |
| 6’6 above | 180 |
#2. Bike Activities
Equally important, the type of riding activities you do with your bike will determine the crankset you choose. In other words, there are different types of cranksets for different bikes.
For instance, a crankset for a mountain bike meant for enduro or downhills ought to be strong. While a crankset for climbing up, such as cross-country racing, should be lightweight.
Lastly, a crank’s size is essential when buying a new one because it affects your paddling flow.
FAQs
How Often Should I Change My Crankset?
You can change your crankset when it’s faulty. But for a busy rider, you should probably change the crank after a 5000 – 6000 miles ride.
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