Jim’s Tech Talk
By Jim Langley
After last week’s column on Dropped Chains with Chain Keepers a reader named “Phil” and Harvey Miller recommended other ways to deal with the problem of dropped chains, front derailleurs and chain keepers. Which is to do away with the double chainring and front derailleur by going to an alternative system.
Front Derailleurs in the Crosshairs
It isn’t a new idea to nix front shifting. I was the new products editor for Bicycling Magazine for 10 years during which I saw thousands of inventions. One came from the Swiss engineer Florian Schlumpf. He came into our office with a very unique single chainring crankset and bottom bracket.
Instead of dust caps covering the bolt holes on the crankarms, his crank had what looked like a raised dust cap on one side and an inset one on the other. But, they were actually buttons that you activated by swinging your ankle in to strike and press in the button. When you did this, you changed the gearing from high to low or vice versa. It sounds difficult but we editors in the office test rode it and it was actually easy to operate and shifted well too. Florian’s invention is still online if you’d like to see it: https://www.florianschlumpf.swiss/index.php/en/bicycle-gear.
Classified’s Powershift Hub
Phil dropped his comment mentioning Classified’s front-derailleur alternative about the same time that RBR publisher Lars Hundley sent me a story about Belgian pro Victor Camenaerts signing on to use the setup for his classics campaign right now. So it’s already being used in the pro peloton.
Ingeniously, Classified has put their double chainring/front derailleur alternative in the rear hub. It’s shifted with a little button that sends a wireless signal to change the gear. They say it happens almost instantly and it can be shifted under full power.
One of the advantages of single chainring systems is that there’s no cross chaining. Cross chaining is when on a double chainring drivetrain the chain is on the small ring and also on one of the smallest cogs, or on the large ring and one of the largest ones. Cross chaining puts stress on the chain which makes for less pedaling efficiency and also increased chances of chain drops and missed shifts.
The cost of the Powershift Hub runs from $1,579 to $3,160 based on what wheel setup you choose since it’s a rear hub based system. Read all about it on their website: https://www.classified-cycling.cc/powershift-technology.
I hope to see and try the Powershift at the Sea Otter Classic next month. In the meantime watch their video to learn more.
I’m a fan of front derailleurs and double chainrings because it’s proven technology, very light and even with cross chaining, the most efficient system. (Cross chaining is easily avoided just by paying attention and not shifting into those gears).
While Classified says the Powershift Hub is more efficient, it actually works like the Sturmey-Archer hubs many of us had on our “British Racer” 3-speeds when we were growing up, remember those?
Inside Sturmey-Archer hubs and the Powershift are sun and planetary gears that by shifting change how hard it is to pedal. If you take apart one of these hubs you’ll see a whole bunch of small geared parts that all fit together and all turn against each other and on axles. You can see some examples here: https://en.wikipedia.org/wiki/Hub_gear. One of the most impressive geared hubs is Rohloff’s Speedhub.
I marvel at how these hubs work and how well they shift. But they are all heavy and every study I’ve seen shows that while they can be very efficient, they can’t match the efficiency of a double chainring/front derailleur drivetrain.
Another consideration is that it looks like Classified’s system requires their proprietary cassette, which could be part of its high cost. It would also mean having to use only their cassettes when you wear one out.
Still, it’s an interesting invention and I hope I get to try it. Maybe we’ll see reports from pro racing on how it’s working.
Reader Harvey Miller gave the nod to a completely different drivetrain since it doesn’t even use a chain. He’s loving his bike with a belt drive. He didn’t say exactly what he has, but I’m guessing since it’s the only one I’ve seen, that he’s using a Gates Carbon Drive. These have been around for many years and proven across many product categories so there’s no doubt it works well.
Here’s how Gates describes it:
Consisting of two metal sprockets and a high-strength belt embedded with carbon fiber cords, Gates Carbon Drive is a low-maintenance, chain-replacing technology from Gates Corp., the global leader in automotive and industrial belts. Clean, quiet, light and strong, Carbon Drive requires no greasy lube, weighs less than a chain and will not stretch. Due to its low maintenance and cleanliness, Carbon Drive is a technology that makes it easier for people to get on bikes.
And here’s an awesome video showing it in use:
I’ve ridden a few Gates Carbon Drive bikes at the Outdoor Demo during the Interbike Bike Show. This was held on dry gravel trails outside Las Vegas. In this harsh environment the belt drivetrains squeaked. You could wash them off with water and quiet them but once they got covered in dust and grit again they squeaked again.
Still, that wouldn’t be a problem for city riding, which is where I think a Gates drive would be a nice feature simply because you’d never need to lube or clean the chain (a belt drive will never rust). Plus, if you came in contact with the drivetrain it wouldn’t make a mess.
But a belt won’t work with derailleurs. So if you want gearing you need to use hub or bottom bracket gearing systems. Which raises the issues of added weight and slight efficiency losses again.
On top of this, because the belt can’t be taken apart, in order to use it you need a frame that comes apart so you can slip the chain onto it.
If I was going to buy one, I would look at complete bicycles. There’s a company in New York City that specializes in them called Priority Cycles: https://www.prioritybicycles.com/.
If you’re already riding a Classified Powershift Hub drivetrain or like Harvey, digging your belt drive, or running another alternative drivetrain altogether please tell us about it in a comment. Thanks!
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.