Making Things Harder
There’s been one customer reaction that surprises me. It’s not the “Wow!” or the “Oh Sh1t!” when someone first tries a Karmic Bikes. That’s the expected reaction. It happens 90% of the time. What I’m talking about is the opposite.
“Can you make this thing harder?”
This request always takes me by surprise, because ebikes are supposed to make things easier right? We try to keep our Level 1 boost equivalent to having good legs, or a slight tailwind behind you. It feels good, but you’re still riding the bike. You’re still doing the work. But when a cyclist rides a Karmic they’ll usually feel like it’s too easy. Like they’re cheating.
The other request is a bit more common, and also not totally unexpected. We design the Koben as a Class 1 bike with a 20mph speed limit. We do this to increase the number of road ways, bike paths and trails you can ride it on. People who want to go faster usually buy our Koben S, a Class 3 bike with a 28mph speed limit. But there are some folks who want to go even faster.
We don’t think going 32mph makes the experience any better. If you ride in a bike lane, you’ll soon realize your fellow bike commuters are traveling about 8–12 mph, on average. If you were actually riding at 28mph (which still requires hard pedaling!) you would be passing everyone and possibly catching some riders off-guard. Just leave the bike-lane bullying to the Cat 6 Racers and Stromer Dads trying to show off. We try to #BeKarmic instead.
Biased Towards Climbing
I’ll admit that top speed was lower on our design brief, since the Koben S was developed in the streets of San Francisco. We’ve made a name for our super-commuter with its hill-leveling superpower. Nothing could stop a rider with the MAX motor in Level 5 and the NuVinci N380 in its “lowest gear”. I’ve ridden up to the top of Lombard Street with tourists snapping pics for fun. It’s kinda our thing as a Silicon Valley ebike startup. Hills? What hills?
We also don’t speed in the bike lanes, and the lights on Market Street don’t really let you get to the high gear/high boost very often. We had to pick a ring and cog size that would optimize the gear range of the N380 for most people, across varying terrain. With the Gates Belt Drive system we couldn’t go smaller than a 24T cog due to the shifter-mechanism at the hub center. We decided to go with a 50T ring, though a larger 55T was available in our crank’s bolt-pattern. The test bikes always rode beautifully at 20–22mph, with a natural pedaling cadence like you would use on a fine road bike.
We Messed Up
Some new Koben S owners were reporting that their bikes weren’t going fast enough. One owner best described it as feeling like she was “missing a gear”. They would be spinning their feet too fast — or more accurately, the bike required pedaling at a very high-cadence just to hit 20-23mph. Something was amiss. We built up a few production bikes in the Karmic Garage and tested them out ourselves. Was our math off? Had we selected the wrong gearing? Why were some bikes unaffected? How many bikes could have these issues? How bad was it? And how would we take care of our owners.
One of our customers sent his bike back and we did a full teardown of the drivetrain to see what could have caused the issue. We found the problem. We tested some solutions and I was able to hit 28mph on his bike. While no one’s getting fired over this (we’re just humans) we found some reasons why the Koben S (v2) wasn’t perfect. Here’s our findings and some solutions:
- Belt Tension — while we asked the factory to tension the belt to spec, we found some variation in the batch. This was a potential problem with the switch to the Gates Belt, but now we know to test for proper tension on our next production run. Gates makes a special tool to test for belt tension, and they even have an App!
Solution: This is the a simple fix similar to how you’d tighten a slack chain on the original Koben S (v1). There are two bolts that hold the dropout hanger on each side. Loosen those, then adjust the tension screw on the front to push the wheel back. Just two to three turns of each screw is enough. You’ll want the belt to be taut, but not binding. Make sure to adjust both sides equally to keep the wheel centered in the frame. Tighten up the four slider bolts with a 5mm wrench. - Shifter Cables — the NuVinci shifter cables have to be set very precisely for the system to work. The underdrive and overdrive cables have a set length of 120mm and 114mm respectively. We found some of the bikes had this set wrong out of the box. If the cable lengths are too long, you would not be able to go into the lowest or highest gear. Adjusting the cable lengths will require a whole post, so stay tuned for that.
Solution: Change the shifter cables, or adjust them to the proper length. (We will be sending out more information about this in the weeks ahead) - Full Overdrive — The N380 hub is shipped from the Fallbrook factory with the hub set to full-overdrive. There is a anti-shift ring that keeps the setting from being changed in shipping. Unfortunately it has to be removed for installing the Gates cog, and this is where a mistake was made. We have a few technicians building our wheels, and a QC manager that overlooks their work. We’re not sure how they missed this, but we will make sure this mistake isn’t made again on our next production run. This is a bit of a complicated diagnosis, but any good bike shop mechanic should be able to confirm and fix it. You can also call us and we would be happy to walk you through the process.
Solution: You should move the shifter into full overdrive (indicator shows cyclist on a flat road). Next you’ll want to remove the rear wheel (15mm wrench), taking off the end nuts and washer. Then removing the nut and shifting mechanism to see the two rings below:
If the marks are aligned, then the hub is perfectly set in “full-overdrive” mode. What we found (above) is that some hubs were not completely set, which meant that you would only get 85–90% of overdrive, effectively lowering the top gear and speed of the bike. A small 10% reduction here would mean a 25mph top speed, instead of the 28mph as designed.
Making It Right
Luckily we have a great community forum where Karmic Owners can share their feedback and ask questions. We started tracking the issues within two weeks of first customer deliveries. We’ve figured out the solutions within a month. I’m really sorry this wasn’t caught earlier at our QA stations at the factory. We will fix it. We will make it right. We will take care of any issues.
The Karmic Experience isn’t just how the bike rides. It starts from the moment you first hear about Karmic Bikes, to the continued joy of riding your Koben many years later. We stand behind our products and we will work hard to ensure our customers are delighted with their decision to be part of our Karmic Family. Thank you again for your continued support.
Cheers,
Hong
