What do you do when you’re riding along and it sounds like someone is eating Doritos inside your rear wheel? Crunch, crunch! If you answered, ‘turn your music up louder’ and keep riding, you’ll probably be replacing your freehub soon. If – like I did recently – you answered, ‘get the pressure washer out and spray all the dirt and sand out of your hub,’ you’ll…well, actually probably be replacing your freehub soon too. When it comes to the maintenance of your freehub or freewheel, neither option is the best.
But, before we start talking about maintenance, repairs or replacing freehubs or freewheels, let’s talk about what they are. What’s a freewheel, what’s a freehub, and how do you know which you have on your bike?
What is a freewheel or freehub?
Unless your bike has internal gearing, all mountain bikes use either a freewheel or freehub. This is a mechanical element on the rear wheel that allows you to stop pedaling even while the wheels continue rolling. If it weren’t for the freewheel or freehub, you would be forced to pedal anytime your bike is in motion. Think of a unicycle or fixed-gear bicycle: there is no such thing as coasting.
A freewheel or freehub works like a ratchet, relying on a system of spring-loaded pawls that engage internal teeth when pressure is applied (during pedaling) but allow the bike to freewheel for coasting. Most bikes with seven gears or less on the rear wheel use a freewheel while bikes with seven or more gears use a freehub or free cassette system. As a general rule, children’s bikes, cheap adult bikes and old mountain bikes (pre-1990s) use freewheels. Most adult mountain bikes made these days use freehubs.
Freewheels and freehubs are different ways of accomplishing the same thing, but they’re not interchangeable. For example, if your bike has a worn out freehub, you can’t replace it with a freehub. If a freewheel wears out, you remove it and completely replace the entire piece, including the stack of gear rings. With a freehub system in need of work, you remove the cassette or gear stack, replace or overhaul the freehub and replace the gear rings.
To dive deeper into the history or functioning of freewheels and freehubs, read this article.
How do you know if you have a freewheel or freehub?
As mentioned above, there are a couple general rules that help determine whether you have a freewheel or freehub.
- Your bike has more than 1 and less than seven gears.
- Your bike is older than from the early 90s.
- It’s a child’s mountain bike or cheap (under $500) adult mountain bike.
If you’re still not sure, or are looking for confirmation of your guess before you buy replacement parts, you can ascertain whether you have a freewheel or freehub – but not just by visual examination.
- Remove the rear wheel from the bike.
- Find a freehub removal tool that fits snugly into the sprocket set.
- Spin the sprockets backwards.
- If the tool spins along with the gear rings then you have a freehub or free cassette system. If the tool stays put while the gear rings spin around, then it’s a freewheel.
Park Tools has a great visual illustration of this on their website to help you tell whether you have a freewheel or freehub.
DIY MTB Pro Tip: Is your Freehub due for an overhaul? Let me help with this article 👉 How to Overhaul a Freehub
Are freewheels or freehubs better?
Freehubs are better for quality, durability and weight. Freewheels are often (but not always) better for affordability.
Since I’m not an engineer, I won’t attempt to determine whether one system is actually functionally superior to the other. But that’s actually a moot point because the bike manufacturing industry has already made that call. Cheaper bikes and kids’ bikes use freewheels, not high-end bikes. Therefore there are no high-end options for picking a nicer or lighter freewheel.
And, freehubs are not universally the more expensive technology. Freewheels cannot be cleaned or repaired. Instead, the entire mechanism needs to be replaced when it gets worn-out or broken. Conversely, it is possible to replace individual parts of a freehub system or to clean and overhaul the existing parts without replacing anything.
Can I put a freehub on a freewheel or vice versa?
Without mincing words: No. A freewheel threads directly on the axle (meaning part of the axle is threaded), while a freehub has splines that line up with matching splines on the cassette. They can’t be used interchangeably.
If you’re really happy with your bike except for the fact that it has a freewheel, it MAY be possible to switch out the rear wheel for one with a freehub – provided the axle is the correct length to fit in your rear dropouts and that you make sure all elements of the drivetrain are compatible.
Are cassettes and freehubs the same?
Cassettes and freehubs are not the same. The cassette is a stack of rings mounted onto the freehub. Some cassettes consist of rings bolted together and some cassettes are rings stacked with spacers between them. But, either way, the cassette has a pattern of ridges, called splines, that allow it to slide onto the freehub in exactly the right position and stay fixed in place with a cassette lock ring.
How do you know when you need to overhaul or replace your freewheel or freehub?
You’ll know you need to overhaul or replace your freehub or replace your freewheel if you notice one or more of the following signs:
- Crunching or grinding sounds when freewheeling.
- Sensation of sand in hub when freewheeling.
- Freewheel locks up.
If you’ve got any of these going on with your freewheel or freehub don’t just turn up your music louder. And definitely DO NOT get out the pressure washer and attempt to wash the sand and grit out. While that seems logical (at least it did to me the first time I encountered it), freehubs rely on an abundant amount of lubrication to keep the internal pawls and teeth moving smoothly. And, since both a freewheel and a freehub are meant to function in a sealed system, they’re not supposed to be washed with water.
If your freewheel or freehub is in need of repair or replacement, we’ll cover those things in our next article, How to overhaul your freehub or replace your freewheel. (second article in series.)
Looking for Some More Ways to Help Your Bike Last
- Regular maintenance will keep you pedaling for years. Read – DIY Mountain Bike Maintenance Schedule
- Everyone wants a new bike, find out when it’s time to buy with this article: Repair Old Bike or Buy New – Options
- DIY Mountain Bike Tune Up – A Complete guide to what to repair and how.
Professional writer Kat Jahnigen was 2 miles from the nearest village – and roughly 2,310 miles – from the nearest English-speaking town – when her bike tire burst. At that time, she was a college student on a bike trip across the desolate, rocky island of Crete. It suddenly occurred to her that it would’ve been good to learn some basic bike repairs before setting off on a solo bike trip.
Check out Kat’s website WriteHire at writehire.net.