The Thorn Mercury 40
The Mercury 40 is designed to succeed the Club Tour Mk5, Audax Mk4, and Mercury Mk3. Drawing inspiration from the Nomad Mk3, it features an integrated frame gate, making it fully compatible with a belt drive system.
IT’S OUR TAKE ON THE ULTIMATE MODERN SPORTS TOURING BIKE
With 650b wheels (or 700 x 40c) it makes an outstanding Gravel Bike.
It also makes a superb bike for lightweight off road touring and a fantastically comfortable bike for cyclists at every level of ability, who ride on today’s broken roads.
Complete Bikes from around £3,300
The Mercury 40 is compatible with both derailleur and Rohloff drivetrains, supports 700c or 650b wheels, and can be configured with drop bars or flat bars to suit your riding style.
Build it with 650b wheels - and can have F&R V brakes, F&R Disc brakes, or Front V and Rear disc. There are different fork options depending on your requirements.
The Carbon disc fork is a QR fork and with 700C you can run 32c tyres and with 650b it will support 38mm tyres.
The frame tubes are of the highest quality - cold drawn, seamless, and heat-treated steel using Thorn 858 tubing as previously used on The Audax frames.
The Mercury 40 is available in a choice of 2 colours , there are 8 sizes - 3 sizes with short top tubes for drop bars, or a relaxed position, 5 sizes with long top tubes for straight bars.
The Mercury 40 has the same geometry as the previous models but with the addition of a Gate in the frame to run a Gates Carbon Belt, and a stand plate under the chain stays so a stand can now be fitted to this bike as this was requested by a lot of our customers.
The Mercury 40 is engineered with a lighter, more responsive frame—delivering an enhanced performance while maintaining the same unwavering commitment to versatility, durability, and comfort. It’s a beautiful well-considered Sports Touring Bike ideal for road or trails, come and give it a test ride.
All Rohloff equipped bike orders come with 100 days moneyback guarantee and derailleur builds come with 14 days moneyback guarantee.
Real Riders, Real Impressions
The Mercury 40 is the latest evolution in Thorn’s line of versatile touring and adventure bikes and it’s already winning the hearts (and legs) of cyclists who’ve taken it on real journeys, from French tours to spirited local rides.
Here’s what riders are saying after putting the new Mercury 40 through its paces...
"Effortless Touring, Unmatched Comfort"
"After my recent tour to Omer in France, the bike performed brilliantly. It just flies along, so easy to cycle."
Nick Ferrar on 09/10/2025
The combination of a thoughtfully engineered frame, Contact Urban tyres and smooth French tarmac resulted in what one rider called “an amazingly effortless ride.” The addition of a belt drive made the journey almost silent apart from the soft hum of tyres on the road.
"Versatility Refined: The Best of Two Legends "
“Out of the three Thorns I’ve owned, I would say this is the most versatile. It seems to have the attributes of the Raven and the Mercury in one.”
Richard Osmond 10/10/2025
Riders who’ve owned earlier Thorn models are particularly impressed. The Mercury 40 with 650B wheels and wider tyres brings together the stability and comfort of the Raven, with the speed and responsiveness of the classic Mercury. Whether it’s cornering through tight turns or cruising long distances, this bike delivers.
"Quiet, Clean, and Low-Maintenance with Belt Drive"
“It is so comfortable on the road and extremely quiet with the belt drive... just the tyre noise."
Nick Ferrar on 09/10/2025
For many, the belt drive is a revelation. No grease, no chain slap — just smooth, silent motion. One rider even reported their son developing "belt envy" after a 20-mile test ride. Once you try it, it's hard to go back.
Comfort Meets Control
“It handled superbly and was a delight to ride - responsive, stable, and lively. The 2” tyres were extremely comfortable.”
Robin Thorn 13/10/025
Paired with the 853 V-brake fork and a chain drive option, the Mercury 40 still gives riders flexibility. Whether you’re a belt convert or prefer a traditional chain, the ride is equally dialled in.
"Built with You in Mind"
“Just a quick note to say thank you for the help you gave me with designing the new Mercury 40. I am delighted with the bike!”
Richard Osmond 10/10/2025
Several customers praised the support and customisation offered during the design process. The Mercury 40 isn’t just a great ride, it’s a bike tailored to your riding style, terrain, and needs.
Final Thoughts...
With its clean lines, custom options, and reputation for touring toughness, the Mercury 40 stands as a new benchmark in comfort, performance, and versatility. Whether you're covering long miles on tour or enjoying a local spin, it delivers an experience that riders are genuinely excited about.