Condensed Answer: Shimano and SRAM 10-speed cassettes can be installed on 8-speed hubs because 8,9 and 10-speed cassettes have similar widths.
However, a Campagnolo 10-speed cassette won’t fit on an original 8-speed hub due to incompatible spline designs.
It’s logical to assume that a 10-speed cassette is wider than an 8-speed model and thus won’t fit on an 8-speed hub.
In practice, however, 8,9 and 10-speed cassettes have a very similar width across popular brands (e.g., Shimano, SRAM).
The sprocket (cog) thickness is kept similar, but the cog pitch is dramatically reduced.
The term cog pitch refers to the center to center distance between two adjacent cogs. It gets smaller and smaller with it each gear increase to allow the user to fit a multitude of cassettes on the same freehub body.
Below is a table containing the data for 10 and 8-speed cassettes:
|Number of Speeds||Sprocket Thickness||Cog Pitch||Total Width|
The difference in total width amounts to (37.2mm-35.4mm) = 1.8mm even though 10-speed cassettes have two extra cogs.
As a result, a 10-speed cassette can fit on an 8-speed freehub body.
The freehub body is the part of the hub on which the cassette slides. It’s also the element that contains the pawls that brush against a ratcheting ring to create the popular buzz sound.
Technically, the freehub body of 8,9,10 and 11 MTB hubs is about 34.95mm. Therefore, a 10-speed cassette does not fit entirely on the hub as there are 2.2mm left.
However, this isn’t a problem because the smallest (last) sprocket of the cassette should not be fully aligned with the freehub body. It should stand a bit taller so that the lock ring can be fully tightened to secure the cassette. Thus, the 1.8mm extra width of a 10-speed cassette doesn’t break the conversion.
8/9/10 Interchangeable Freehub Bodies
Another “clue” that clearly indicates that a 10-speed cassette would fit on an 8-speed hub is the availability of freehub bodies marketed as compatible with 8/9/10 speed drivetrains.
The Benefits of Installing a 10-speed Cassette on an 8-speed Hub
The compatibility between 10-speed cassettes and 8-speeds hubs saves money when upgrading to a 10-speed drivetrain because you don’t have to purchase a 10-speed specific hub.
10-speed cassettes have two extra gears that could be much larger than what we find on 8-speed cassettes. For example, one can easily locate a 10-speed cassette with a 42t cog.
Thus, if you want extra low gears, a 10-speed cassette is a legit option. The other is to get a smaller chainring.
Smooth Gear Jumps
10-speed cassettes offer smaller gear jumps and thus make it easier to maintain a high cadence.
Cadence is the number of crank rotations per minute. High cadence (e.g., 90RPM) is considered superior because it results in greater average speeds, energy savings, and lower joint stress.
The Downsides of Installing a 10-speed Cassette on an 8-Speed Hub
10-speed specific freehub bodies often have taller splines. This is done intentionally to prolong the life of the freehub body.
The cogs of a 10-speed cassette are known to make cuts/dents into the freehub body because they’re thinner than 8-speed models (1.6mm vs. 1.8mm) and thus sharper.
Therefore, one could expect faster wear of the freehub body when combining a 10-speed cassette with an 8-speed hub.
That said, the wear accumulates slowly and it’s hard to say whether that’s a major negative.
All The Parts Needed For an 8-to-10 Speed Drivetrain Upgrade
If you’re upgrading from 8 to 10 speeds, the following parts will be required:
- a 10-speed shifter (unless you plan on using friction shifters that can support a 10-speed cassette)
- a rear derailleur with extra range or a derailleur hanger extender for your existing derailleur
- a 10-speed chain (10-speed cassettes need narrower chains due to the smaller cog pitch)
- a 10-speed cassette
If you want to run a single chainring, you will also need:
- a narrow-wide chainring
- а chain guide
Summary: What You Need To Know
- A 10-speed cassette can be installed on an 8-speed hub as long as the hub isn’t made for a very old system.
- 8, 9 and 10-speed cassettes are quite similar in total width because the distance between the cogs gets smaller with every speed increase.
- One can find freehub bodies directly marketed as 8/9/10 speed compatible.
- 8-speed freehub bodies have lower splines and thus are more prone to damage induced by the narrower and thus sharper 10-speed cogs.
- 11-speed MTB cassettes are also compatible with 8-speed hubs.
- 11-speed road cassettes are not compatible with 8-speed hubs (read more)