Freewheels versus cassettes, chainring dimensions and BCD (I’ll explain), e-bike chains versus regular bicycle chains, mechanical versus hydraulic disc brakes, disc brake pads, handlebar dimensions (I’ll explain this too in a moment)… this is harder than servicing computers because computer manufacturers mostly comply with industry standards and form factors. Bicycle manufacturers, on the other hand, are all over the place. But, on the flip side, I’m a ‘problem solver’, so this sort of chaos actually makes the sport of e-bike building interesting for me!
So what’s happening? First, my Build #3 mid-drive is popping the chain off in the high gears. Chain alignment problem I think, so I’m sorting that one out with a different chain ring, rear cassette (changing out the 9-speed cassette for a 7-speed cassette plus shifter), and e-bike-rated chain. We’ll see how that goes and if all the effort is for naught. (Note: It was – for naught)
Build #2 is getting a new controller, display, and throttle (arrived yesterday and will be installed today). I also removed the front derailleur and (warped) chainring and will install the new chainring/crank arriving today. So two lessons learned here:
- The 52 tooth chain ring I purchased first doesn’t fit. The chain stay on this frame extends out too far and the chain stay interferes with the large chainring. I’m not sure how I would have tested this in advance of buying the large chainring, but apparently I can only use chainrings with smaller outer dimensions, OR one with a different offset. SO the new chainring coming today will have both and we’ll see how that works out. Note: for an e-bike, having three speeds on the front chainring isn’t needed due to the extra power provided by the motor, so eliminating the complexity of that and the associated derailleur seems/seemed like a good idea. (And it was – a good idea and worked perfectly! Success…)
- When buying a chainring, modularity seemed like a good idea, so I’m buying a crank with a 104 BCD (Bolt Circle Diameter) bolt spacing that allows me to substitute other chainrings that conform to this bolt pattern. Whether or not this new crank and chainring system works for my application, I’ll find out soon enough. The crank needs to clear the pedal assist sensor, and the chainring needs to clear the chain stay. Fingers crossed! It just might work out… PS – There are MANY crank bolt patterns and sizes, so this particular lesson took a while to figure out which was best for my application.
Replacing the rear cassette on Build #3 will happen today, so we’ll see how that goes. It has been a while since I have had to do this. I was rebuilding freewheels all the time when I was racing bicycles at Penn State, but that was a while ago. The technology has changed a bit. (Failure: The new cassette was narrower than the original and I didn’t have the right spacers, so I’m sticking with the original 9-speed cassette and shifter)
And the last thing I’ll cover for today’s post is the handlebar (and handlebar stems). I like ‘adjustable’ handlebar stems and am having good luck with this one. But there are two dimensions when buying a handlebar stem to be aware of. First is the handlebar diameter 31.8mm (1.25”) at the center of the handlebar where it attaches to the handlebar stem, and second is the front fork stem diameter 28.6mm (1-1/8″). Get out your trusty digital caliper and make sure you know what your specific measurements are. Also, how wide do you want your handlebars to be? I purchased this handlebar ’cause it was a really good price and it fit the stem I already had. Two problems:
- It was wider than I had anticipated so I cut two inches off either end with a pipe cutter. After a bit of cleanup, the handlebar was (almost) perfect.
- Here’s the ‘almost’ part. The taper from the center of the handlebar continues out some distance (due to the wider handlebar design), making installation of things like handlebar-mounted bells and lights problematic. Many of these accessories are designed for a certain handlebar outer dimension. Still, I like this handlebar and I think it’ll work fine, but I’m having to adapt to its design now that it has been cut down for my application.
Regarding brakes, I’m still figuring this one out. Rim brakes (Build #3), mechanical disc brakes (Build #2), a mix of rim and hydraulic disc brakes (Build #1), disc size, brake pad composition, etc. are all being used. I’ll have to get back to you on this. It gets complicated…
**update**
And what’s with this “narrow-wide” chainring thing?
“The term “narrow wide” chainring describes the shape and profile of the individual teeth driving the chain. Each tooth alternates thickness, narrow wide narrow wide, all the way around the ring. With an old school traditional chainring, all the teeth would be considered narrow with small differences in thickness between brands.” (source)
The sole purpose of the narrow wide chainring is chain retention. The narrow wide tooth pattern keeps the chain from moving left to right and eventually popping off the chainring while riding.
And there’s more: Did you know that there are different chains depending on how many sprockets your freewheel or cassette has? I hadn’t really given that much thought, but now I have to. Some chains, like the Zonkie I use a lot, say they’re made for 6, 7, or 8 sprockets, and I find they work well for my 7-sprocket rear-hub e-bikes. However, Build #3 is a mid-drive that uses the existing 9-sprocket cassette which means I should be using a chain like this one, designed for 9 sprockets. Plus, when running a mid-drive kit, a chain designed to handle the abuse a mid-drive can dish out is essential. This particular 9-speed KMC chain looks like it’s up to the task. (And it was. It shifts well, is quiet, and stays on the Lekkie narrow-wide chain ring really well. This seems to be the perfect chain for my application!)
