Grin Bikes: New manufacturer from Germany: Grin bikes for big enduro adventures

Many bikers dream of creating their own mountain bike at some point in their lives. When the first prototype of the Grin One Enduro bike was unleashed on the trails in 2022, this dream became a reality for Philipp Brunn. Although the Bavarian by choice with roots in the Odenwald started his initially private project on a blank piece of paper, he was not completely naïve. Philipp has 20 years of professional experience in the automotive industry and started building his own enduro bike as a hobby during the coronavirus pandemic.

As a passionate bike mountaineer, Philipp was dissatisfied with the increasingly flatter and heavier enduro bikes on the market and designed his own fully without further ado. In March 2023, the further concept was finalised based on the findings of the prototype. At the end of July, Philipp was then able to give several bikes in the second stage of development to his experienced biker friends for testing. The next prototype stage is scheduled for mid-2024. Production of series bikes is scheduled for early 2025.

Philipp Brunn currently runs the Grin Bikes project part-time from home. The great enthusiasm of the bike community for his Grin One Enduro could change that one day. Philipp is not alone and is very well connected. His girlfriend regularly accompanies him on test rides in alpine terrain, he is part of the bike mountaineering group around Munich and has good contacts in the lively scene in Eberbach.

The well-founded feedback he receives for the prototypes of his first work is continuously incorporated into its further development. The prototypes are welded in Karlsruhe, while chassis specialist Anyrace from Munich helps with the development of the chassis.

Details of the Grin One prototypes

• Price: Prototype not yet for sale
• Suspension travel: 170 millimetres front / 160 millimetres rear
• Wheel size: Mullet - 29 inch front / 27.5 inch rear
• Frame weight: 3.2 kilos
• Weight of complete bike: from 14 kilos
• Special feature: In-house development from Europe, space for telescopic seatposts with up to 240 millimetres stroke, size-dependent chainstay length

Grin One - a unique prototype

The Grin One has some unique selling points that set it apart from other current enduro bikes. It was important to Philipp to combine the downhill expertise of this category with good uphill performance. Despite the robust aluminium frame, he therefore attaches great importance to a low frame weight and is aiming for 3.2 to 3.3 kilos. In its current configuration, the prototype bike weighs around 14 kilos without a single carbon part.

An extra steep seat angle of 78.5 degrees should make the enduro bike efficient even on the steepest climbs. As Philipp regularly tackles high-percentage climbs himself, he pedals the Grin One on a small chainring with only 26 teeth. A maximum of 32 teeth would be possible.

For plenty of freedom of movement over the bike and the lowest possible standover height, it relies on steeply sloping top tubes and straight, extra-short seat tubes (440 millimetres in size L). At the same time, it allows the use of adjustable seat posts with a maximum stroke of up to 240 millimetres.

Geometry & details of the Grin One Enduro (prototype)

The Grin One is designed for a mullet wheelset so that the rear wheel does not have to confront the rider's rear end on steep descents. Chainstays that grow with the frame size should nevertheless give the Enduro balanced riding characteristics - regardless of the rider's height.

At 489 millimetres in size L, the reach is modern and roomy. The steering angle of the prototype is slack at 63.8 to 64.5 degrees, but is not quite as extreme as many competitors in the same suspension travel class. Another special feature is the moderately low bottom bracket height. As a bike mountaineer, Philipp knows that a bottom bracket that is too low can restrict the handling of an enduro bike in rough terrain.

The small chainring also provides more ground clearance. After all, the Grin One should be able to do more than just shoot downhill fast: bike park stunts, adventure tours and bike mountaineering expeditions should be equally possible.

As befits a modern mountain bike, the prototype of the Grin One Enduro has a UDH derailleur hanger at the dropout and internal cable routing. The rear triangle is compatible with both air and steel spring shocks.

Speaking of the rear suspension: Philipp favours soft spring rates to make it easier to roll over obstacles. The rear suspension is therefore designed for a lot of negative suspension travel (SAG) to guarantee traction at all times in demanding terrain. Nevertheless, the linear kinematics should become significantly more progressive towards the end in order to cope well with large impacts. With ASTM category five approval, the Grin One should be able to handle even the wildest action.