The Weird Compatibility Of 11-speed Hubs (part 1)

from Rookie’s keyboard,

Hello, friends

Today’s lesson is about 11-speed cassettes and their overall “weirdness” from the perspective of compatibility. I think that many of you will be interested to learn the technicalities below.

Let’s go.

Cassette and Freehub Body Width


Despite what one may naturally assume, the widths of 8/9/10 and 11-speed cassettes are very close. The primary dissimilarity is the cog pitch (the center-to-center distance between two neighboring cogs). 

Cassettes with more gears have a shorter cog pitch to fit the extra cogs within roughly the same space. (For that reason, chains designed for cassettes with a greater number of speeds have narrower outer plates.)

This property makes MTB 8/9/10 and 11 cassettes compatible with 8/9/10 and 11-speed MTB freehub bodies.

The freehub body is the section of the hub on which the cassette slides. It also contains the engagement pawls that brush against a ratcheting ring inside the hub and create the popular sound that rear hubs are known for.


This is where things get interesting. 11-speed road cassettes are different. 

The 8,9 and 10spd road cassettes and hubs are similar to one another, but the 11-speed hubs are 1.85mm wider. 

This isn’t “accidental”. The extra space is there to push the largest sprocket of the cassette away from the spokes and eliminate possible contact with them.

Road cassettes have a smaller large sprocket (e.g., 26T) than MTB models. Consequently, the periphery of the large sprocket is close to the section of the spokes going into the hub.

When pedaling in 1st gear(largest sprocket), the chain could rub against the spokes and damage them over time.

Mountain bikes don’t have this issue because they have a much larger 1st gear (e.g., 42t) which easily clears the spokes. 

What is the “moral of the story”?

If you want to install an 8/9/10-speed cassette on an 11-speed road hub, you will need a 1.85mm spacer.

Why 1.85mm?

To find out the width of the spacer, we need the following data:

  • The width of a 10-speed freehub body
  • The width of an 11-speed freehub body

The difference between the two widths determines the size of the spacer.

11-speed freehub bodies are about 36.75mm whereas 10-speed freehub bodies are 34.95mm.

The difference is 1.8mm.

Note: Without the spacer, you won’t be able to tighten the cassette. The cassette will move across the freehub body and cause bad shifting and instability.

Why Install Fewer Gears?

Let’s be honest. Installing fewer than 11 speeds on an 11spd hub seems somewhat illogical. Why would you want to do it?

Well, I can think of the following situations:

  • You already have the parts and need to get your bike running ASAP.
  • You are building a beater bike made of whatever parts you have.
  • You are at a location where you can’t find anything else (e.g., touring on Mars).

The downside of a similar practice would be the bigger the jumps between the sprockets. Larger jumps make it more difficult to maintain a consistent cadence(rotations of the cranks per minute). Cyclists obsessed with optimal cadence might consider that a massive downgrade.

In general, a high cadence such as 90RPM is considered ideal for maintaining a high average speed as efficiently as possible. 

As Always Campagnolo Is Different

Unlike Shimano and SRAM’s cases, you can’t mount 8spd Campagnolo cassettes on an 11spd hub because Campy’s 11 and 8spd hubs have a different spline architecture. An 8-speed Campagnolo cassette won’t fit.

That said, it’s technically possible to put 8 speeds on an 11-speed hub even when using Campagnolo components. But you will need a hack.

If you remove the largest sprocket from a 9-speed cassette (Veloce/Mirage/Miche) and then add a spacer to make up for the gap, you can fit the cassette on an 11-spd Campy hub and still have 8-speeds.

Well, there you have it, friends.

Keep in mind that this is part 1. I have more to say on the topic in the future. But for now, that’s enough.

Until next time, 







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