A 9-speed Shimano or SRAM MTB cassette can be installed on a 10-speed Shimano or SRAM MTB hub right away.
A 9-speed cassette is wider than a 10-speed road cassette and is therefore too big for 10-speed specific Shimano road hubs.
A 9-speed Campagnolo cassette can be installed on a 10-speed Campagnolo hub.
MTB Cassettes and Hubs Compatibility
8/9/10 and 11-speed MTB cassettes and hubs are cross-compatible. This is achieved via the following modifications:
- Smaller cog pitch with each gear increase
The term cog pitch refers to the center to center distance between two adjacent cogs.
By reducing that number, one decreases the overall width of the cassette and makes it possible to fit more cogs within the same space.
The table below contains the cog pitches of 8,9,10 and 11-speed MTB cassettes.
| Number of Speeds | Cog Pitch | Total Width |
| 8 | 4.8 mm | 35.4mm |
| 9 | 4.35mm | 36.5mm |
| 10 | 3.95mm | 37.2mm |
| 11 | 3.9mm | 40.6mm |
Тhe difference in terms of thickness between a 9-speed and 10-speed MTB cassette is 0.7mm (37.2mm-36.5mm).
This isn’t substantial enough to make a 9-speed incompatible with a 10-speed hub.
The 9-speed cassette is narrower, but its smallest cog is still at the sweet spot – ever so slightly taller than the freehub body. As a result, the cassette lock ring can successfully tighten the sprockets to the freehub body.
FAQ: What is a freehub body?
The freehub body is the part of the hub on which the cassettes slide.
The freehub body has splines guiding the cassette and acting as anchor points for the cogs.
Also, the freehub body contains spring-loaded pawls which brush against a ratchet ring to create the popular buzz sound that rear hubs make.
- Thinner Sprockets
With each gear increase, the sprockets of a cassette get thinner.
The table below contains the data for 8,9,10 and 11-speed MTB cassettes:
| Number of Speeds | Sprocket Thickness |
| 8 | 1.85mm |
| 9 | 1.78mm |
| 10 | 1.6mm |
| 11 | 1.6mm |
The goal behind the thinner sprockets is to keep the overall width of the cassettes close.
Road Cassettes and Hubs Compatibility
In the road segment, the game is a bit different due to the presence of 10-speed specific road hubs.
Initially, 10-speed road cassettes were installed on 9-speed hubs with the addition of a 1mm spacer.
The 1mm spacer was needed because the 10-speed road cassettes ended up narrower than the 9-speed cassettes.
However, there was another problem that couldn’t be solved with a spacer – the thinner and thus sharper sprockets of 10-speed cassettes were quickly damaging the splines of the freehub body.
To solve this issue, Shimano designed a 10-speed specific hub. The new freehub has taller and thicker splines that make it a lot harder for the sprockets to cause damage. Also, the freehub is shorter and made of two segments.
Consequently, you can’t install a 9-speed cassette on a 10-speed road Shimano hub.
FAQ: Can I install a 9-speed Campagnolo cassette on a 10-speed Campagnolo hub?
Yes, 9 and 10-speed Campagnolo cassettes are cross-compatible. However, you cannot install a 9-speed Campagnolo cassette on a non-Campagnolo 10-speed hub.
What Are The Benefits of Installing a 9-speed Cassette on a 10-speed Hub?
- Money-savings
Cross-compatibility gives freedom to the customers and allows them to re-cycle different parts.
It’s also worth mentioning that 9-speed drivetrains are cheaper to maintain in the long run because the parts (cassettes, chain, derailleurs…etc.) cost less in comparison to their 10-speed equivalents.
What Are The Downsides of Installing a 9-speed Cassette on a 10-speed Hub?
From a technical perspective, there are no downsides to installing a 9-speed cassette on a compatible 10-speed hub.
That said, there are downsides to using a 9-speed cassette over a 10-speed one.
Those would be:
- Bigger jumps. 9-speed cassettes come with larger jumps making it harder to maintain high cadence.
The term cadence refers to the rotation of the cranks per minute. High cadence (e.g., 90RPM) is associated with greater average speeds, less fatigue, and lower joint stress.
- Extra range. 9-speed cassettes often come with a smaller low gear than 10-speed models.
Summary: What You Need to Know
- A 9-speed MTB cassette can be installed on a 10-speed MTB hub right away.
- A 9-speed cassette cannot be installed on a 10-speed specific Shimano road hub because the hub is too narrow.
- 10-speed road specific cassettes are about 1mm narrower than 9-speed cassettes and the 10-speed specific Shimano road hub reflects that.
- A 9-speed Campagnolo cassette can be installed on a 10-speed Campagnolo hub.
