11/128" Drivetrain - Narrowing the Gap

Real world Insights from Pre-Paris Olympic Testing from Tait Somervell (New Zealand Team mechanic) 

Is an 11/128” Drivetrain the Secret Weapon for Your Track Bike?

Track cycling is all about precision, speed, and efficiency - every millisecond counts. When it comes to your drivetrain, every detail matters. The long-standing standard has been the 1/8" setup, valued for its durability, strength under high torque, straightforward maintenance, and forgiving chainline tolerance. But what if there’s a way to save a few extra watts and gain performance without sacrificing reliability?

Enter the 11/128” chain. Once a staple of road cycling and most often seen on 11-speed drivetrains, this narrower option is now available in compatible single-speed track components. In this post, I’ll share the pros and cons of running 11/128" on the track, based on my experience as a mechanic and from testing it in the lead-up to the Paris 2024 Olympic Games.

Is It worth switching to an 11/128” drive train on your track bike?

As track cycling tech evolves, so does the search for every marginal gain. One setup that sparked our interest at CNZ was the 11/128” chain, a narrower, lighter and more aero alternative to the traditional 1/8” drivetrain. Not to mention the added efficiency numbers published in academic research papers.

How We Tested It

In the lead-up to Paris, we gradually introduced the 11/128" drivetrain. Riders first used it during warm-ups to get comfortable, before moving into light efforts and full testing. We also spoke with mechanics from other national teams who had already been experimenting with this narrower setup, adding valuable perspective to our own trials.

We learned that this drivetrain performs but setup is key to gaining all the benefits.

What to watch for

The most important aspect to be vigilant for is the chainline and tension sensitivity. The narrower tooth profile means that even the smallest misalignments can cause unwanted noise and accelerate cog wear. This ultimately leads to reducing the efficiency gained by switching to a narrow drivetrain. 

The 11/128" system takes a little more precision over the standard 1/8", especially when fitting or adjusting chain tension. That being said, as with most high-performance upgrades it becomes second nature with experience.

Runwell tools have developed a handy chainline gauge tool for quickly measuring the chainline on your bike. The card is placed around the seat tube, and an indicator points exactly to 42mm including a ± 2mm tolerance.

For further assistance check out our Chainline for Marginal Gains blog.