Three viewpoints in half a day, a quarter of an hour from the shop: Fort du Saint-Eynard perched on its cliff above Grenoble, the alpine pastures of the Charmant Som, then the Col du Coq at the foot of the Dent de Crolles. Seventy-four kilometres of bends — and, above all, time to stop.
🏍️ Included in the €49 discovery deal. 65 km leaves you more than 25 km of margin on the 100 km included: enough to linger at the fort, climb gently up to the Charmant Som, take time for a drink in Saint-Pierre-de-Chartreuse and make every photo stop you feel like, without ever watching the odometer.
The loop in detailLa Tronche, Saint-Eynard, Col de Porte, Charmant Som, Saint-Pierre, Col du Coq65 kmapprox. 1 h 50
La Tronche → Fort du Saint-Eynard — 11 km, 20 min. You leave the shop through Corenc and Le Sappey-en-Chartreuse, then the Saint-Eynard road clings to the cliff all the way up to the fort, at 1,325 m.
Saint-Eynard → Charmant Som via the Col de Porte — 12 km, 25 min. Back down to Le Sappey, up to the Col de Palaquit and then the Col de Porte (1,326 m), where the narrow Charmant Som pasture road begins.
Charmant Som → Saint-Pierre-de-Chartreuse — 11 km, 20 min. Down from the pastures into the village — the place on this loop to stop for a coffee on a terrace.
Saint-Pierre-de-Chartreuse → Col du Coq — 7 km, 20 min. The finest technical stretch of the ride: narrow, shaded, the Dent de Crolles straight ahead.
Col du Coq → La Tronche — 24 km, 25 min. A long descent towards the Grésivaudan valley, Belledonne facing you, then back to the shop.
The Chartreuse, beyond the road
The massif is more than a ribbon of asphalt: limestone cliffs, high pastures and summits closing the horizon at every bend. Here is what you ride past on this loop.
The Charmant Som alpine road, six kilometres above the Col de Porte. Photo Gemini1980 — CC BY-SA 4.0, via Wikimedia CommonsChamechaude, the highest point of the Chartreuse, seen from the Charmant Som. Photo Gemini1980 — CC BY-SA 4.0, via Wikimedia CommonsThe Dent de Crolles and its cliffs, which you skirt on the way down from the Col du Coq. Photo Eusebius — CC BY 3.0, via Wikimedia CommonsThe valley from the Col du Coq, at 1,434 m. Photo Patrice78500 — CC BY-SA 3.0, via Wikimedia Commons
Photo stops not to be missed
The viewpoint at Fort du Saint-EynardGrenoble a thousand metres below, the Vercors opposite and the Drac–Isère confluence: the most spectacular view you can reach by motorcycle around the city.
The stone gateway to the fortThe passage cut into the rock, just before the car park. Lovely light in late afternoon.
The hairpins on the Charmant Som roadA narrow road, tight hairpins and pastures all around. Pull into a wide spot to frame the bike against the slope.
The end of the Charmant Som road, 1,670 mChamechaude, the Dent de Crolles and, on a clear day, Mont Blanc. The valley of the Grande Chartreuse monastery opens up a few steps further on.
The Col du Coq, 1,434 mThe wall of the Dent de Crolles above you, turning orange at the end of the day.
What you will see along the way
Fort du Saint-Eynard, Grenoble’s balcony
Perched at 1,325 metres on the ridge overlooking the Grésivaudan, the fort is earned by a small cornice road up from Le Sappey-en-Chartreuse. It was built between 1873 and 1879 as part of the Séré de Rivières system, and is one of the seven forts in Grenoble’s fortified belt. It could house close to 480 men and twenty-five artillery pieces tasked with locking down the roads into the Chartreuse. It never fired a shot: aviation made it obsolete, and the army decommissioned it in 1962.
Arriving at Fort du Saint-Eynard, flags in the wind, after the hairpins up from Le Sappey.The stone-cut entrance to the fort, just before the viewpoint.At the fort’s viewpoint, Grenoble and the Isère valley a thousand metres below.The fort’s parapet, straight above the Grésivaudan.At the viewpoint, the bike facing the valley.
Today it belongs to the Grenoble landscape. You park at the foot of the ramparts and the panorama opens up through 180 degrees: Grenoble a thousand metres below, the Vercors opposite, Belledonne to the left, the Isère valley running off towards Chambéry. A museum and a restaurant open in summer. It is a quarter of an hour from the shop, and yet you feel a very long way off — check the opening times on chartreuse-tourisme.com before riding up.
The Charmant Som pastures
From the Col de Porte, a pasture road climbs another six kilometres and stops at 1,670 metres, below the summit of the Charmant Som (1,867 m) — one of the most visited viewpoints in the massif, and one of the very few you can almost ride to. In summer, willowherb turns the slopes pink and herds often stand on the road: this is a working alpine pasture, not scenery.
A stop below the cliff, between the fort and the Col de Porte.A pause at the signposts, at the top of the Charmant Som road.Willowherb in the foreground and the Tiger Sport at rest, on the Charmant Som road.Ready to set off again, the alpine road straight ahead.Backlit at the hiking signposts, at the top of the road.
From the car park, the view swings round to Chamechaude, the Dent de Crolles and, on a clear day, Mont Blanc. A few steps are enough to discover the valley of the Grande Chartreuse monastery, invisible from the road — exactly the kind of ten-minute detour that justifies the mileage margin of the half-day on its own.
The Col du Coq, for the way back
Nine narrow, shaded kilometres from Saint-Pierre-de-Chartreuse, with the Dent de Crolles growing at every bend, then a long descent towards the Grésivaudan. You close the loop without ever riding the same road twice.
End of the day on the way back, when the light turns orange.
A half-day that leaves you time
Two and a half hours of riding across half a day: that is the whole point of this loop. The distance sits well inside the 100 km of the discovery deal, and the time left over is yours — a coffee on a terrace in Saint-Pierre, a pause at the fort, and as many photo stops as the light deserves. Allow generously rather than tightly: these roads are not to be rushed, and that is exactly right.
Good to know before you set off
65 km: the loop sits comfortably inside the 100 km included in the €49 discovery deal.
Allow 1 h 50 of actual riding, without pushing. Route planners suggest close to two hours: doable if you know the road, not if you are discovering it, and not behind a camper van on the Charmant Som climb.
The Charmant Som road closes in winter and can stay snow-covered late into spring. Best season: June to October.
The Saint-Eynard and Charmant Som roads are narrow and busy with walkers at weekends. Set off early and take a wide line through the hairpins.
Herds are up on the pastures from June to September, often on the road itself.
Frequently asked questions
Is this loop covered by the €49 discovery deal?
Yes, with room to spare: 65 km against 100 km included. It is in fact the loop we recommend for a first half-day, because it leaves time for the stops.
Can I ride it on an A2 licence?
Yes. The Triumph Tiger Sport 660 and the Street Triple 765 R are available in A2; on a full A licence, the Trident 800 is perfect for this kind of route.
Can you ride up to Fort du Saint-Eynard?
Yes, the road is open and surfaced all the way to the fort car park, and you park at the foot of the ramparts. The last section is a narrow cornice: take care, especially on the way down. It closes in winter.
Can you visit the fort and the Charmant Som?
Fort du Saint-Eynard has a museum and a restaurant open in summer; the Charmant Som is a working pasture, freely accessible, with an easy path to the 1,867 m summit from the end of the road. Both are very busy at weekends in high season: set off early and you will have the road and the panorama to yourself.
Where can I stop for a drink?
In Saint-Pierre-de-Chartreuse, halfway round, or at the Fort du Saint-Eynard restaurant if you would rather have the view than the village.
Ready to ride?
The bike is waiting for you in La Tronche, prepared and insured. Pick your date and your slot, morning or afternoon, and set off on this loop.
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