Drivetrain Parts for High-Power Hub Motors: Freewheel, Cassette and Chain Choices
A high-power hub motor puts a lot of load through the parts you pedal with. If you are searching for a 10 speed freewheel, or trying to work out whether you need a freewheel or a cassette at all, this guide covers the choices, how they fit together with your chain, and the HPC parts worth a look.
Freewheel or cassette: what is the difference?
Both give you a set of rear cogs for pedaling. The difference is how they mount to the wheel. A freewheel is a self-contained block of cogs with the ratchet built in, and it threads onto the hub. A cassette slides onto a freehub body on the hub, and the ratchet lives in the hub itself. Either way, you pedal through a derailleur, a chain and a set of cogs.
Here is what HPC can tell you on the fitment question: HPC's high-power hub motor kits use freewheels, and HPC also offers options that can use cassettes. Which kit or hub takes a freewheel and which takes a cassette is something to confirm with HPC when you order, so you buy the right part the first time.
Why drivetrain parts matter on a high-power build
A hub motor drives the wheel directly, so pedaling gears are there for your legs, not for the motor. Even so, a fast, heavy bike puts real demands on the chain, cogs and derailleur, and a high-power build is a different animal from a standard commuter. Chain stretch, skipping under load and a chain that fails are the problems this guide is trying to help you avoid.
If you are still deciding between a freewheel and other gearing, such as an internal hub or a two-speed bottom bracket drive, read our comparison first: E-Bike Gearing Compared: 10-Speed Freewheel vs Rohloff vs Schlumpf. This post stays focused on the parts themselves.
The Sunrace 10 speed freewheel, 11-36T
The Sunrace 10 Speed Freewheel, 11-36T is HPC's 10 speed freewheel for e-bike builds, priced at $95. From the product page:
- Range of 11-36T, with cogs of 11-13-15-17-19-21-24-28-32-36.
- Compatible with both SRAM and Shimano shifters.
- A smaller 11T cog than most freewheels, which HPC says gives you more pedal power.
That 11T top gear is the point for a fast bike. A smaller cog means you can keep pedaling usefully at higher speeds before your legs spin out. Availability of individual parts varies, so check the product page for current status.
Cassette options
If your build is set up for a cassette, HPC lists several. These are the ones on the site today:
- SRAM PG720 DH cassette, $40.
- SRAM PG1130 11-42T cassette, $90.
- SRAM EX1 cassette, 10-48, $450.
The product pages are the place to confirm the details of each one, including speed count and what it fits. If you are weighing a wide-range 12-speed setup, our post on the Shimano SLX 1x12 drivetrain upgrade walks through that route.
Match the chain to the cogs
This is the rule that matters most: the chain has to match the number of speeds on your freewheel or cassette. Chains get narrower as the speed count goes up, so a chain built for the wrong number of speeds will shift poorly and wear fast. Pick the cogs first, then pick a chain that is made for that speed count.
HPC carries several KMC chains:
- KMC E10 Turbo E-Bike Chain, 136L, 10 speed, $55. HPC describes it as an e-bike specific chain with double X bridge construction and high pin power riveting, tested by HPC up to 4000 watts.
- KMC E11 E-Bike Chain, $48. A 136 link chain at 247 grams. Note that KMC's own description is written around e-bikes with mid-mounted motors, so confirm it suits your setup.
- KMC E12 E-Bike Chain, $75.
- KMC X 10.93 Chain, $30.
For a 10 speed freewheel, a chain listed for 10 speeds is the match, and the KMC E10 is the one on this list that says so. Read each chain's page for the speed it is made for before you buy.
Chain length, wear and care
- Get the length right. The KMC chains above are listed at 136 links. Your frame, wheel size and cog range decide how many you actually need.
- Replace chains early. A stretched chain wears the cogs down with it. A fresh chain is cheaper than a new freewheel.
- Keep it clean and lubed. See our guide to cleaning and lubing your e-bike chain.
- Check your shifter and derailleur. The Sunrace freewheel works with SRAM and Shimano shifters. HPC also lists a SRAM GX 10 speed rear derailleur at $80.
Do not forget the rest of the hub motor setup
Drivetrain parts are only one piece of a hub motor build. If you are planning a complete kit, our post on the High Performance Hub Motor Conversion Kit covers what is in the box, speed, range and power options. The kit itself is priced at $1,999.
High power also means high axle torque, which is a frame and dropout issue as much as a drivetrain one. Read our hub motor torque arm guide before you ride a powerful hub motor.
How to choose
- Confirm your hub type with HPC. Ask whether your kit or hub takes a freewheel or a cassette.
- Pick the cogs. For a freewheel build, the Sunrace 10 speed 11-36T is the starting point.
- Match the chain to the speed count. A 10 speed chain for a 10 speed freewheel.
- Check shifter and derailleur compatibility before ordering.
- Replace the chain on schedule to protect the cogs.
Prices are as listed on the HPC site at the time of writing and may change. Availability varies by part, so check each product page.
Ride responsibly
High-power hub motor builds can go far beyond the legal definition of an electric bicycle in the US (750W, with assisted speed capped at 20 or 28 mph). Use them on private property, closed courses or approved off-road areas, wear full protective gear, and check the rules where you live. A drivetrain that fails at speed is a safety problem, so inspect your chain and cogs regularly.
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