Kevin of Steel 4 Frameset

The new KOS4 keeps the same spirit as the last Kevin of Steel: a reliable, versatile, heat-treated chromoly steel gravel bike built for real adventures, long rides, rough roads, bikepacking, commuting, and whatever else you define as gravel this week.

But it has been brought properly up to date.

The geometry now follows our current titanium GXR4, our flagship gravel platform. That means a proven gravel fit, wider tyre capability, improved handling, and a higher front end on the larger sizes compared with the previous Kevin of Steel. The size range has also grown, with XXS and XXL now available in limited numbers.

The KOS4 features increased tyre clearance, clearing up to 700c x 51 mm / 29 x 2.0” at the rear, with room for even more up front — up to 29 x 2.4” with the Ride 415 fork. KOS4 also gets internal dropper post routing through the bottom bracket shell, so you can get low if the trail gets rowdy.

We kept Kev on leave by the pool until the new design passed the standards we expect from a true Curve adventure bike, including full ISO 4210 compliance. That took longer than planned. Nearly three years, in fact. We now truly understand why so many brands neglect thorough testing for steel bikes - it’s tough! But if Kevin was going to come back, it needed to be done properly. The KOS4 frame uses top tube and down tube gussets to improve durability and help the frame meet our strict testing requirements. 

Mounting points have also been improved. The KOS4 includes rear rack mounts, fender mounts, top tube bento mounts, and five bidon mounts, including the offset down tube mounts popularised on our GMX+ model. The offset and underside down tube mounts allow riders to run three bottles while still using a full-size frame bag, even for smaller frame sizes, giving you more range on bikepacking adventures.

Up front, the KOS4 is built around the Ride 415 VGM fork. It is a serious fork, with tyre clearance up to 29 x 2.4”, adjustable offset, and Curve’s through-leg VGM mounts. Each fork leg is rated to carry up to 8 kg, giving riders a total of 16 kg of fork-mounted load capacity. Extra water, micro-panniers, fire extinguishers, full-sized pumpkins - go for it. The Ride 415 has also been to MTB standards meaning it’s a super robust gravel bike upgrade.

At the back, bespoke cast dropouts bring SRAM UDH and Transmission (T-type) derailleur compatibility to the steel Kevin platform, just like its titanium cousin. Kevin has always been versatile. Now it is more compatible with modern drivetrains too.

We are relieved and proud that The Kevin of Steel is finally back from sabbatical! Now stronger, more capable, and even more reliable.