Yesterday, a friend texted me asking for bike mechanic knowledge and assistance. He’d bought a 10-speed cassette on sale, but the seller had told him that his hub may be incompatible with his new acquisition (what a fancy word).
“What was your previous cassette,” I asked him.
“An 8-speed Shimano model,” he responded.
“Buy me a chocolate bar, and I will come over to install it,” I said.
“Deal.”
“EZ money,” I thought, and ended up being right. (I love that.)
I don’t know why the seller was worried about the compatibility between a 10-speed cassette and an 8-speed hub.
The truth is that the hubs of Shimano and SRAM designed for 8/9/10 have functionally the same width and spline architecture.
And you can slide a 10-speed cassette on an 8-speed hub directly without any “bike mechanical” sorcery. That’s exactly what I did in this case.
That said, I did some research online and found one exception – the good old Campagnolo is different once again and doesn’t fit in this rule.
A 10-speed Campy cassette has a different spline arrangement than an original 8-speed model, and I am afraid, you will need a dedicated 10-speed hub for that conversion.
Time for some“Scientific Research”
I know that some of you won’t be satisfied with a “it just works” explanation, and I have prepared a bit more data for that exact purpose.
The first principle that you have to be aware of is:
- The overall width of 8/9/10-speed SRAM and Shimano cassettes (and other equivalents) is functionally the same.
It’s weird I know. It’s normal to expect cassettes with more gears/cogs to be wider, and they are, but minimally.
| Number of Speeds | Sprocket Thickness | Cog Pitch | Total Width |
| Shimano 8-speed | 1.8mm | 4.8mm | 35.4mm |
| Shimano 10-speed | 1.6mm | 3.95mm | 37.2mm |
| SRAM 8-speed | 1.6mm | 4.8mm | 35.4mm |
| SRAM 10-speed | 1.8mm | 3.95mm | 37.2mm |
The table above contains three critical measurements – sprocket/cog thickness, cog pitch, and total cassette width.
The sprocket thickness and the total width are somewhat obvious. The cog pitch is a less-known measure.
The cog pitch is the center-to-center distance between two cogs.
So, 10-speed cassettes are only 1.8mm wider in total than 8-speed models. The difference is real but not enough to make an 8-speed hub incompatible with a 10-speed cassette.
The freehub body (the part on which the cassette slides ) of 8/9/10-speed MTB hubs is about 34.95mm wide. A 10-speed cassette is therefore 2.2mm wider.
However, you will also notice that the 8-speed model is wider by about 0.9mm too.
Why? Because the smallest sprocket of the cassette (highest gear) should stick out a bit so that the lock ring can be fully tightened to secure the cassette to the hub.
Precisely for that reason, the 1.8mm extra width of a 10-speed cassette doesn’t change much.
But what about the rest of the components…
You got me. A cassette swap is not enough for a full 8-to-10-speed conversion.
So, that chocolate bar wasn’t as easy to get after all.
The rest of the conversion required the following parts and steps:
1. Removal of the old shifter + installation of the new 10-speed unit. (This is needed because the system is indexed.)
2. A new 10-speed chain. You can’t use an 8-speed chain with a 10-speed cassette. The 8-speed chain is wider than the 10-speed model and would rub against the cogs.
In this particular case, the derailleur was capable of handling the 10-speed cassette because it’s an 11-28.
But if you’re switching to a massive MTB cassette such as 11-42, you may have to replace the derailleur too…or install a derailleur hanger extender that would position the derailleur lower and increase its max cog capacity.
Truth be told, this isn’t the most groundbreaking upgrade out there. The main benefit would be the smaller jumps between the cogs making transitions and continuous rhythmic pedaling easier.
So, if you care about your cadence (RPM) go for it. Don’t expect miracles, though.
TL DR;
- 8-speed Shimano/SRAM hubs are 10-speed ready
- 8-speed Campy hubs can’t accept 10-speed cassettes of any kind
- 10-speed cassettes improve your cadence…but who cares?
All that matters is that I got my chocolate bar and helped a friend. It’s the time together that’s priceless.
Until next time
– rookie
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