After selling 4 million Oi bells, Knog has re-engineered a classic

The Knog Prima is a completely redesigned take on Knog's original Oi bike bell – a product that has sold more than 4 million units worldwide since its debut.

Described by the brand as a “classic re-engineered”, the Prima has been in development for more than two years and reflects extensive feedback gathered about the original.

“For something so simple, it was a nightmare to get right,” Knog CEO Hugo Davidson told BikeRadar. “But we’re so proud of it.”

At a glance, the Prima retains the minimalist, wrap-around aesthetic that made the Oi so popular, but it has been fundamentally reworked to address both performance and durability.

Louder and cleaner

One of the biggest changes is the bell’s new hammer mechanism. The new hammer is a dual-material, over-moulded structure, with a metal interior, that stores more energy as it’s pulled back, then accelerates into the anula (striking surface) with greater force.

Davidson explains: “[The new design] gives a weighted end to the hammer, and the point at which the hammer stops means that when it’s pulled back, it over-extends and accelerates.”

The result is a louder, crisper tone – peaking at over 85 decibels, with around 4 to 5dB more output than previous designs. 

The new design also solves one of the original Oi’s most persistent problems: over-stretching the spring. “The hammer is specifically designed to ensure you can't overextend the spring. It also hides the spring, unlike the last one, so aesthetically it's a much cleaner unit,” Davidson says.

Built to last

Knog says the Prima has been subjected to thousands of consecutive rings to verify long-term performance.

“When you go into the testing lab in the factory,” Davidson explains, “they have this [bell] sitting on repeat, repeat, repeat for thousands and thousands of rings. 

“This tests things like the wear on the pins, simulating accelerated life of maybe four or five years. We needed to make sure everything would retain its integrity over that time.”

The Prima also benefits from a redesigned mount. A new hinged clamp improves bar compatibility and makes installation simpler and more secure. 

According to Davidson, this was another user-led improvement: “It also means the way in which it’s assembled and tightened up on the bar is much less problematic for people.”

Refined styling

Beyond the mechanical changes, Knog has also focused on visual refinement. The bell’s lower housing draws inspiration from jet engine air intakes, adding a subtle curvature and creating a more pronounced shadow line beneath the bar.

“When I was looking at it initially, we were taking inspiration from things like a jet engine intake,” Davidson says. “That sort of conic shape around the base lifts the handlebar and gives it more air and shadow when mounted – it’s a little more refined than the previous model.”

From an industrial design standpoint, Davidson says the team’s goal was clear: “We went back and said we need to improve on every level – the look, the packaging, the materials. Everything.”