Catchy titles notwithstandiing, freewheels aren’t sexy. But if you’re using a rear electric hub motor you’re probably still going to need ‘em, so it’s worth understanding a bit about cheesy ones and really good ones. Because most of what’s out there now is pretty cheesy.
First, let’s be clear about what freewheels are, and how they differ from cassettes. Freewheels are the traditional way of putting multiple cogs on a rear wheel. Freewheels screw on to the hub, and the ratchet mechanism that lets you coast is built in to the freewheel body.
Nearly all non-electric rear wheels sold for bikes in the last several years use cassettes instead. Shimano’s patented cassette and freehub approach puts the ratchet in the hub itself instead of on a screw-on freewheel body. This lets the cassette be just a bunch of cogs that slide onto a splined hub; it also allows the outboard wheel bearing to be located farther outboard, reducing the load on the axle. This makes it practical for regular axles to accept 8, 9 or even 10 cogs without breaking (long a known problem for freewheels with more than 7 cogs.)
Because the freehub and cassette design is superior, the market for freewheels has shrunk dramatically. Typically only the very cheapest new bikes now ship with them. Component manufacturers recognize this and build products priced to match their markets. It’s the rare freewheel today that isn’t designed for a department store bike.
But electric rear hubs still use ‘em. (Hard to say whether it’s due to patent issues with Shimano, lack of space for the motor’s bits, or not wanting to create user-serviceable rear hubs (as they would likely need to be with the freehub mechanism in there.)
Enter SunRace. SunRace is one of the few that markets 8- and 9-speed freewheels. They’re pretty widely available on eBay, and they’re the 8- and 9-speed freewheels distributed by Bionx. If you look closely in the picture below, you’ll see that these appear to be conventional 7-speed freewheel bodies with a couple of more cogs added to the outboard end.
I tried several of these on my own Bionx system. None of them failed. They all worked. And they all drove me crazy – that’s why this one is on a paper towel and not on a bike. They sounded and felt cheap when spinning them on your fingers (even after lubing them heavily.) More important, they made awful clicking noises when pedaling them down the road (especially on the smaller cogs.) I nearly drove my dealer crazy swapping out 8- and 9-speed SunRace freewheels while we tried to figure out if the noises I kept hearing were coming from the freewheels or my pricey electric hub. I think the bearing noises I heard may have been related to the pedaling torque sometimes being applied inboard of the freewheel bearings, but also being applied well outboard of them when using the smaller cogs. If you can find a good alternative, I recommend using it.
In desperation, I ordered a very different kind of freewheel – a 7-speed Defiant freewheel by Interloc Racing Design. They aim at the classic bike replacement part market rather than the mass market. They’re a lot more pricey, but I think they’re worth it. As soon as I spun one on my fingers I could hear it was in an entirely different league. (Think closing the door on a new Mercedes instead of closing the door on an old Ford Escort.) All I hear when I pedal on my bike now is quiet and smooth shifting.
If you’re retrofitting one of these you do need to think about 7-speed compatibility with your current shifters and chain. I prefer bar-end shifters and friction shifting anyway, so there was no compatibility issue for me; you might need to pick up a suitable 7-speed shifter. I did swap my 8/9 speed compatible chain for a 7 speed compatible chain. (They’re more durable, anyway.) The odds that you’ll miss an 8th or 9th gear on your electric bike are pretty slight. More likely, you’ll miss the ability to get an 11-tooth sprocket on there. (Too bad that the classic Shimano Megarange 11-34s are no more.)
I would avoid old stock on the IRD Defiants — they had a high failure rate on their Mark I product, but they’re up to Mark III or Mark IV now and seem to be past those problems. I’ve heard that other importers may have 8/9 speed freewheels now as well. Got any experience with them? Any other freewheeling thoughts? Please share them in our discussion forums at http://ElectricCyclist.com/forum.