Imagine the Swedish landscape and a stereotypical scene of idyllic red cottages with white trim, foregrounded by a lake of glimmering blue, might spring to mind. Beyond perhaps, adding depth, lies a band of birch and spruce, and a midsummer view of wooded islands.

Now, add to this image the sight of two half-naked men lunging from a tiny sauna cabin into the cold shock of a lake. One screams. The other ducks his head under, pops up, shivers, then does it again. His skin has the pinkish tinge of salmon, but he’s smiling.

Those swimmers are my friend John and me (I’m the one grinning), and we’re quickly learning that the subversive joy of cold-water swimming – and stripping off in nature – are Swedish obsessions.

We’re on the first day on the Lelångenleden, a 112-mile (180km) cycle route of newly linked trails, which takes riders from the Bohuslän coast, north of Gothenburg, through the lakes of Dalsland and deep into the coniferous forests of Värmland, where the country is wilder still. The promise is traffic-free gravel roads and a segment that runs along the embankment of the discontinued Lelången railway, as well as a journey punctuated by stops in lake towns so charming they could easily be creations of Pippi Longstocking author Astrid Lindgren.

But we’re up for a sterner challenge than the recommended four-day itinerary. Our plan, researched and booked online using West Sweden Trails’ helpful planning tool, is to split the route into three sections of about 40 miles each and cycle for up to five hours a day. Along the way, we’ll be staying in quiet hotels and a campsite where the food is as important as the lake setting.

“You won’t be alone,” says Erik Josefsson, founder of the Dalsland Experience, the tour organiser and bike shop that rents us our gravel bikes and bikepacking gear – for the next three days, we’ll be living out of frame and saddle bags. “Why not?” I ask Josefsson, a little disgruntled. “Sorry, I meant to say there’s plenty of wildlife in the forests!” comes the reply.

West Sweden’s burgeoning cycling scene is largely thanks to the ambition of the regional tourist boards. Now in development, the Västkustleden will be a new national cycle path between Gothenburg and the Norwegian-Swedish border, while the 105-mile Ljungleden opens this month and links together two of Sweden’s most popular trails (the Kattegattleden in Gothenburg and the Ätradalsleden in Falköping). More and more Swedes want to spend their summers cycling, and the Lelångenleden – affordable, family-friendly and largely flat – is tipped to become the next top-tier trail.

We start in the coastal village of Uddevalla, overlooking the beaten metal blue of the Byfjorden, setting off from the Strandpromenaden, a beautiful seaside boardwalk below granite cliffs – a few years ago, it was named Sweden’s most beautiful road. Then, before we head north, a 15-minute detour takes us to Gustafsberg, Sweden’s oldest seaside resort, with a beach, a jetty, a colony of crimson-tinted bathhouses and a historic lido converted into a hostel.

After four hours in the saddle, the fully serviced eco-campsite at Ragnerud Lake, at the foot of the Kroppefjäll plateau in Färgelanda, is a welcome stop for our first night. We check in to a cosy red cabin, then take canoes out on the lake and enjoy a restorative sauna, before watching the sun’s glorious rays cresting the treetops as the light fades. There is a very special quiet and otherworldliness to Sweden in the late summer.

Overseeing this wilderness are campsite owners Linus Bergström and Marielle Örtengren, who grew up on the lake, and the location offers access to one of southern Sweden’s largest hiking destinations. On their doorstep is 200m years of geology and 80 miles of trails.

The campsite’s sustainable restaurant Ragnerud Kök showcases the gifts of the forest – mushrooms, lingonberries, dill flowers. We share plates of kroppkaka (boiled potato dumplings) with chanterelles and brown hazelnut butter, and beef with beetroot and mushroom cream. Then it’s lingonberry-poached pears with forest marmalade. “We hike, we pick mushrooms. Then there is the pure thrill of jumping into the cold lake,” says Linus. “We love the simplicity of the forest and the slow pace of life.”

On untamed gravel roads the next day, red waymarkers guide us to the Dalsland Canal, a system of natural lakes and locks connecting 157 miles of waterways, where cold water swimmers regularly strip off, leaving John looking sheepish. Our cycle route soon morphs into the canal towpath, and we pass a lock house turned summer cafe that’s selling waffles and ice-cream, and lock keeper’s cabins of stone, wood and iron, which can now be booked for overnight stays.

At the end of the 19th century, the variety of terrain – bristling forests, silent mountains, quivering lakes, almost alpine landscapes – prompted Prince Eugen of Sweden and Norway to describe Dalsland as a microcosm of his homeland. As a prominent landscape painter, the prince captured the soul of the place better than most, and his description fits the Sweden we wheel through. With more lakes than anywhere else in the country, our map shows hundreds of spreading fingers, with depths of inky blue.

We stop for the night in the former lumber town of Bengtsfors, checking in at First Hotel Bengtsfors before heading for dinner at Storgatan 19, a cocktail bar with a menu fit for a Tour de France winner. “Seasonality is vital,” co-owner Oliver Tveter tells us, and I order a lifetime-best skagen (prawn salad, but served on a potato pancake) and fallow deer with pickled pumpkin.

The woods around the town are so vast, breathing and beckoning that they can fool you into believing you are being followed, especially in the slanting, shifting early morning light. For all that, it’s not frightening, but a landscape that enlivens the senses. Often, there are roe deer running earnestly across the road – once, I brake hard to avoid a collision.

What’s more, there is a sense that time is not linear in Dalsland. When we cycle deeper into the dense coniferous forests on our last day, it is as if the clock has been wound back. The red barns and lonely church on Lake Västra Silen look like period pieces. When we surface again from the woods to arrive in a blaze of Lycra in the little mill town of Gustavsfors, we have to push onwards for our fika (social coffee break) as it’s Sunday and all the cafes are shut. Any thought of modern-day Sweden has largely been erased.

On our last afternoon, near journey’s end in Värmland, the gravel slowly welcomes us back into the 21st century. I had worried there wouldn’t be enough to do on our trip, but in the end there are so many interruptions – lakes that quiver like jelly, photo stops for elk signs, cold swims everywhere – that we have to clock-watch until the end.

As we reach the road to Årjäng, where our trip finishes, I gaze back and strange half-certainty comes to me. That I’ll return to west Sweden as soon as I can – maybe even on a bike.

The trip was provided by West Sweden tourist board. The Dalsland Experience organises guided and self-guided itineraries and rents gravel bikes and bikepacking gear. Itinerary planning information can be found at Lelångenleden. Ragnerud camping pitches from £20; cabins from £75. Doubles at First Hotel Bengtsfors from £96 B&B. Lock keepers’ cottages from £200