It's tempting to make the Onion joke about Gillette here Why it makes perfect sense for this bike to have two gears and two chains Bike design seems like a solved problem, but there's a lot to learn from Buffalo. Kevin Purdy Feb 4, 2025 1:17 pm | 0 Credit: World Bicycle Relief Credit: World Bicycle Relief Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn moreThe Buffalo Bicycle Utility S2 has won an award from Eurobike and earned a German Design Award. With components designed by cycling industry giant SRAM and made from heavy steel, the bike has rim brakes, two gears, two chainrings, and two separate chains. And that makes total sense.The S2 is the second bike developed by World Bicycle Relief, which aims to bring bicycle-based mobility to the nearly 1 billion people who otherwise must walk long distances for basic needs. YouTube channel Berm Peak recently featured (and rode) an S2 (as first seen at Hackaday) and explains why a bike with two chains makes sense. Short answer: redundancy, reliable shifting, and far more simple repair. Berm Peak's tour and explainer on the Buffalo Bicycle S2 Utility. Buffalo bicycles are meant to take people a long way over tough terrain, hauling whatever they need to haul. Given that the rear rack is rated for 200 pounds, that "whatever" can range from cargo to humans. The original Buffalo bike had a single gear and coaster brakes, which as both kids and minimalist bike fans can attest, make it simple to stop and go. Buffalo bikes can generally be fixed with the single included wrench, but World Bicycle Relief has also been training mechanics (over 3,300 now) and setting up some 200 Buffalo-focused bike shops.The S2 model aimed to give riders an uphill climbing gear, but without introducing the complexities of a gear-shifting derailleur, tensioned cables, and handlebar shifters. Engineers at SRAM came up with a solution that's hard to imagine for other bikes, but not too hard to grasp. A freewheel in the back has two cogs, with a high gear for cruising and low gear for climbing. If you pedal backward a half-rotation, the outer, higher gear engages or disengages, taking over the work from the lower gear. The cogs, chains, and chainrings on this bike are always moving, but only one gear is ever doing the work.Seth at Berm Peak suggests that the shifting is instantaneous and seemingly perfect, without clicking or chain slipping. If one chain breaks, you can ride on the other chain and cog until you can get it fixed. There might be some inefficiencies in the amount of tension on the chains, since they have to be somewhat even. But after trying out ideas with simplified internal gear hubs and derailleurs, SRAM recommended the two-chain design and donated it to the bike charity.Buffalo S2 bikes cost $165, just $15 more than the original, and a $200 donation covers the building and shipping of such a bike to most places. You can read more about the engineering principles and approach to sustainability on World Bike Relief's site.Kevin PurdySenior Technology ReporterKevin PurdySenior Technology Reporter Kevin is a senior technology reporter at Ars Technica, covering open-source software, PC gaming, home automation, repairability, e-bikes, and tech history. He has previously worked at Lifehacker, Wirecutter, iFixit, and Carbon Switch. 0 Comments