As you’ll note from the pictures, Gravaa looks like a normal bike hub, albeit slightly larger than a standard one. As Gertjan explains, it is in fact a normal bike hub, just a massively tech-upgraded one. It’s self-contained, so it works with any bike and when it’s not doing anything it doesn’t add any friction whatsoever. There’s a module inside the front and bike hub, with the front hub acting as the master, and the rear the slave - the front wheel dictates the pressure for both. An antenna on the hub connects the wheels via bluetooth. “The only thing remaining are the controls, which consist of a ring shifter for a mountain bike, or if you have drop bars, a wireless module and small cable which pops into the end of one of the drops, and two buttons, one which sits on the right of your bars for increasing tire pressure and one on the left for decreasing it.”
There’s an app, too, which users can download from the Apple or Google stores and set up their user details which also registers and activates the warranty for Gravaa. The user can add details such as bike weight, riding style and so forth which will create a profile that includes suggested tire pressures. Once connected, these settings will automatically pass to Gravaa, which will kick in to maintain the predetermined pressure should their tires suffer a puncture and some pressure loss before their sealant can plug the hole. “The other way of using Gravaa,” notes Gertjan, “is to operate everything manually, using the handlebar controls to increase or decrease tire pressure at will. A lot of people do that.” Importantly, even under manual control, if the system detects a drop in pressure, it will kick in to pump the tires back to the pre-determined level.
