Condensed Info: The standard/default BMX chain is 1/8” (3.2mm) wide. There are also narrower 3/32″ (2.4mm) chains designed to save weight.
BMX Chain Width
Bicycle chains have two widths – inner and outer. The outer width represents the distance between the external/outer plates.
The inner width is the spacing between the inner plates.
The size of a chain refers to the internal width of the chain. If the chainring and/or the rear cog are tоo wide for the inner width of the chain, the combination will not work.
The most common BMX chain size is 1/8” (3.2mm).
However, there are also 3/32″ (2.4mm) and 3/16” (4.8mm) chains. The purpose of 3/32″ chains is to save weight. That is achieved by producing a narrower/skinnier chain that doesn’t require as much material.
Meanwhile, 3/16” chains are built for strength. Hence why they’re thicker and heavier.
Weight Comparison
The table below compares the weight of all three BMX chain sizes.
| 1/8” (3.2mm) | Weight | 3/32″ (2.4mm) | Weight | 3/16” (4.8mm) | Weight |
|---|---|---|---|---|---|
| Wippermann conneX 100 | 403g (110L) | KMC K1 Narrow | 377g (100L) | KMC 415H (98l) | 800g |
| K1 Wide | 411g (110L) | Shadow Conspiracy Interlock V2 RACE | 362g (98L) | ||
| Mission 410 | 329g (102L) | KMC HL810 | 385g (100L) | ||
| Odyssey Bluebird | 263g (100L) | IZUMI Izumi-V | 362 (116L) | ||
Note: The data in parentheses indicates the number of links that the chain has.
Conclusion: 3/32″ chains are not always lighter than 1/8″ chains. In fact, there are 1/8″ models that weigh less than their 3/32″ rivals.
Meanwhile, 3/16” are not only heavier but also hard to find.
1/8″ vs 3/32″ Chains: What’s Best?
1/8″ chains dominate the BMX market for the following reasons:
- Strength
All things being equal, a thicker chain is a stronger chain.
- Cross Compatibility
If a chainring designed for a 1/8″ chain is combined with a 3/32″ chain, the teeth of the chainring won’t fit between the inner plates. Thus, the combination is unusable.
However, a 3/32″ chainring can be combined with a 1/8″ chain. Some people say that the combination will result in a sloppy feeling (side to side play) as well as faster wear of the chainring’s teeth, but many cyclists have done it without experiencing major issues.
The success of the combination is highly dependent on the model of the chain and the chainring.
For best results and maximum safety (lower chance of a dropped chain), it’s best to combine a 1/8″ chain with a 1/8″ chainring.
- Availability
Since 1/8″ chains are the standard, the demand and the supply are high. Consequently, riders can choose among many models. 3/32″ chains are rare due to the low demand.
- Weight
As mentioned, 1/8″ chains are not necessarily heavier than 3/32″ models. Thus, the main advantage of 3/32″ chains is smaller than some riders believe.
- No Shifting
Another advantage of 3/32″ chains is that they’re more flexible laterally. This property facilitates shifting and is therefore beneficial to geared bicycles.
But since classic BMX bikes have no gears, the extra flexibility of 3/32″ chains is inconsequential.
FAQ: How to find the width of a chain?
Option 1: Labels
The easiest way to find the width of a chain is to read the label. Most models have either a 1/2″ x 1/8″ or 1/2″ x 3/32″ indication.
The first number (1/2″) indicates the distance between the chain pins whereas the second (1/8″ or 3/32″) specifies the width of the chain.
Option 2: Measure the Inner Width of the Chain
If you’re trying to specify the width of a chain without original packaging, you can use a digital caliper to measure the distance between the inner plates.
Option 3: Measure the Rear Cog
Another option would be to measure the thickness of the rear cog. In general, rear cogs designed for 1/8″ chains are about 3mm thick. Meanwhile, 3/32″ cogs are usually a bit over 2mm thick.
FAQ: How long should my chain be?
The length of a BMX chain is dependent on the following parameters:
- Cog size
- Chainring size
- Chainstay length
A bike with short chainstays and a small chainring will need a shorter chain than a bike with longer chainstays and a bigger chainring.
To cover all bases, new chains are much longer than a bike needs them to be. It’s up to the user to shorten the chain with the help of a chain tool.
The process is described below:
Step 1: Slide the rear wheel forward towards the bottom bracket.
Step 2: Put the chain over the cog and the chainring.
Step 3: Take a short but strong wire and make two 90-degree bends on both ends. (You can use a cut spoke).
Connect one end of the wire to a chain-link closer to the chainring.
Connect the other to a chain-link closer to the rear cog. Ideally, the chain will be slack but not too much.
Step 4: Slide the wheel back to tension the chain.
If the connection points are too far apart, you won’t be able to tension the chain. If they’re too close, you won’t be able to move the rear wheel much. If you experience those issues, one of the connection points needs to be changed.
Step 5: Determine where the two ends of the chain should connect to maintain the desired chain tension. Then cut the chain with the help of a chain tool.
For a more clear demonstration, watch the video below:
