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Definitions:

2 Piece Cranks

2 piece cranks consist of two distinct parts – a “free” crank arm plus a crank arm with a spindle/axle attached to it.

3 Piece Cranks

3 piece cranksets include 3 elements – 2 separate/free crank arms plus a spindle/axle.

The Advantages of 2 Piece Cranks

The benefits of 2 piece cranks are:

1. Simpler Installation

2 piece cranks are a bit easier to install because one of the crank arms is already hydraulically pressed or welded to the spindle and does not require additional adjustment.

The attached crank arm increases comfort because it can be used as a handle when getting the spindle through the bottom bracket.

2. Extra Stiffness

In theory, 2 piece cranks should be stiffer because the spindle is integrated into one of the crank arms and thus the power transfer during pedaling is stronger.

In reality, however, this is a highly questionable point. If a 2 piece crankset and a 3 piece crankset are installed properly, most people will have a difficult time saying which one is stiffer during a blind test.

3. Light Weight

2 piece cranks usually weigh less because the spindle has a larger diameter and thus can be hollow and light but also very strong. The absence of a pinch bolt on the arm pre-attached to the spindle saves some weight too.

Having said that, not all 2 piece cranks are lighter than the 3 piece versions. Ultimately, it depends on the model.

The table below compares the weights of popular 2 piece and 3 piece BMX cranksets:

Conclusion: On average, the 2 piece cranks in the table are 97 grams lighter than the 3 piece models. However, as you can see, there are some very light 3 piece cranks too.

It’s also worth mentioning that heavier cranks aren’t as much of a detriment as one may think due to the position of the weight – in the middle of the bike.

If the extra weight was near the front or back, it would have a greater significance.

The Disadvantages of 2 Piece Cranks

The downsides of 2 piece cranks are:

1. Inability to Remove Both Crank Arms

The structure of 2 pc cranks makes it impossible to remove both cranks arms since one of them is machine pressed into the spindle.

Therefore, if that crank breaks or cracks, you will have to buy a new set.

(Another option would be to search for a spare on the second-hand market.)

2. Higher Price

2 piece cranks tend to be more expensive than 3 piece cranks.

Of course, the final price depends on the model and the brand.

3. Fewer Options

3 piece cranks have been the standard for a long time. (2 piece cranks are technically new.)

In consequence, there are more 3 piece cranks on the market.

4. Non-replaceable spindle

If the spindle of a 2 piece crank breaks or malfunctions, it’s game over, and you have to replace the entire set.

Conversely, the spindle of 3-piece cranks is replaceable as long as you can find a new one.

The good news is that spindles are tough. It’s somewhat common to break a bottom bracket, but the spindle/axle requires some exceptional misfortune and crashing to “fall down”.

The Advantages of 3 Piece Cranks

The pros of 3 piece cranks are:

1. Modularity

If the crank arms or the spindle break, you can replace the damaged part without having to purchase a new set of cranks.

2. Classic

3 piece cranks have been here for a long time and have already proven themselves as very strong and reliable.

3. Greater Variety

3 piece cranks are very popular. The market offers a large variety of models.

4. Affordable

You can find decent 3 piece cranks for a fair price.

The Disadvantages of 3 Piece Cranks

The cons of 3 piece cranks are:

1. More Tinkering

Since one of the crank arms is detached, it takes a bit more work to mount the cranks.

2. Heavier Weight

As already shown, 3 piece cranks are heavier on average.

So, what’s best?

If you want a simple and light crankset that you can disassemble with an Allen key as quickly as possible, 2 piece cranks fit the bill.

If you want a classic BMX crankset with modularity and do not care about having the lightest bike, a 3 piece crank should be more than satisfactory.

As far as strength is concerned, both options will perform very well as long as the quality is good.

FAQ: Can I convert from 2 piece cranks to 3 piece cranks?

Yes. But you will have to replace the entire crankset and potentially the bottom bracket. Therefore, it’s more of a switch/upgrade than a conversion.

If the current bearings and sleeves fit the new cranks, you should be able to use the existing bottom bracket.

FAQ: What about 1 piece cranks? Are they strong?

Оne piece cranks are the cheapest but unfortunately the weakest too. For that reason, they are found on children’s bicycles as well as low-quality models.

1 piece cranks stopped being used for serious BMX riding during the late 80s.

The main incentive to drop them was their weakness (frequent bending) plus the fact that they are difficult to tighten.

1 Piece Cranks vs. 3 Piece Cranks

1 piece cranks made of Chromoly steel could be surprisingly strong.

However, they can’t match the strength of quality 3 piece cranks.

The other downsides of 1 piece cranks are:

• They tend to spin when doing tricks.
  
• When they break, you have to replace the entire set. Conversely, 3 piece cranks are made of replaceable parts.

• One-piece cranks have non-sealed bottom bracket bearings that get contaminated easily. In different, 3 piece cranks come with sealed bearings protected from the elements. The result is smoother pedaling.

• 1 piece cranks tend to be heavier and do not have a warranty whereas quality 3 piece cranks do.

• If you go for 1 piece cranks, you will be restricted to 1/2″ pedals. Meanwhile, 3 piece cranks offer the widest variety of pedals.

• One-piece cranks require a large bottom bracket and aren’t compatible with most models on the market.

The pros of 1 piece cranks are:

• Low price

• Retro/old-school look that is hard to replicate with modern cranksets

Ultimately, 3 piece cranks are vastly superior to 1 piece cranks. Having said that, bikes with 1 piece cranks are still usable and can do the trick for children and beginners.

However, 1 piece cranks will inevitably break or at the very least start to “complain” as you progress. When that happens replace them with decent 2 or 3 piece cranks.

FAQ: What’s a 2.5 piece crank?

2.5 piece cranks are in-between 2 and 3 piece cranks.

By default, one of the arms comes attached to the spindle via a bold-based wedge system. If you want, you can remove the crank arm.

Many people prefer 2.5 piece cranks because they offer the benefits of both worlds.

FAQ: What’s the best crank arm length?

Most BMX cranks range between 160 and 180mm.

The benefits of shorter crank arms are:

• easier to do tricks involving crank spins
• heel clearance (you’re less likely to hit the rear peg with your foot)
• stiffness (shorter levers are stiffer)

The benefits of longer crank arms:

• faster acceleration thanks to greater mechanical advantage
• stability

Riding vs. Obsession With Components

Far too many people get caught in the search for the ultimate bike.

We want everything to be perfect, from the chainring bolts to the grips, and become so obsessed with an illusory image that we forget the most important part – riding.

It’s essential to have quality components, but past a certain point, the tinkering converts from helpful action into over-thinking. Go ride.