Mason Cycles’ road & gravel bikes keep evolving with larger tires, modern geometry & more hauling capacity to extend their adventure capabilities. Now the new ISO takes #AdventureSport riding further afield In Search Of even more off-road trails to explore with dropbars, 29er or 27.5+ wheels, and some trick detailing…

Mason Cycles ISO 29/27.5+ steel bikepacking mountain bike

Mason Cycles ISO 29er 27.5+ steel bikepacking adventure gravel dropbar mountain bike

Mason Cycles started out developing the Definition and Resolution disc brake road bikes with larger tires to open up more places to ride year round. That quickly evolved into the 650B Bokehs for gravel adventures. And now the new ISO expands adventure trail riding even further off-road. The new ISO is an even more progressive bike for Mason, with a new Dedacciai steel frame and carbon fork design that can fit wide 29er tires or even full plus-sized 27.5 tires to take on ever steeper & rougher terrain on bikepacking adventures far from tarmac. beyond just adding a lot of mounting points for accessories, Mason added a few extra tricks including a unique lightweight, load-bearing front fender that will make taking loaded bags much more secure off-road.

Mason ISO bikepacking bike Tech Details

The new Mason ISO is built from a custom-shaped & butted Dedacciai Zero steel tubeset developed for Mason, plus a mix of a Reynolds 853 seattube, a stainless bottom bracket, and UK-made Mason x Bear flat mount dropouts. This unique tubing design & spec is really one of the key places where Dom Mason’s years of frame shines, setting his bikes apart.

The bike gets triple Anything cage mounts on both top & bottom of the downtube, plus forward-facing on both fork legs, in addition to standard seattube bottle bosses. Both frame and fork also get braze-on mounts for both full coverage fenders and front & rear racks.

Mason Cycles ISO 29er 27.5+ steel bikepacking adventure gravel dropbar mountain bike Shutter

The Boost-spaced frame uses an integrated headset for the 1.5″ tapered steerer fork. That new carbon Hot Shoe fork is suspension corrected for a 100mm travel fork (if you decide to go that way) and gets internal routing for a dynamo for extended off-road touring.

Mason Cycles ISO 29er 27.5+ steel bikepacking adventure gravel dropbar mountain bike Shutter fender

Strapped onto the Hot Shoe fork is the unique new Shutter Mudguard, an integrated fender that can support 500g of load and includes lash down loops.

Mason Cycles ISO 29er 27.5+ steel bikepacking adventure gravel dropbar mountain bike

The ISO routes the rear derailleur and brake internally (or internal Di2), and includes mixed internal/external routing to run a stealth dropper seatpost. The bike is optimized for 1x drivetrains, but it can be configured with a band clamp front derailleur too. The bike gets a threaded 73mm BSA bottom bracket and uses a 31.6mm seatpost.

Mason Cycles ISO 29er 27.5+ steel bikepacking adventure gravel dropbar mountain bikeThe ISO is designed to fit up to 29 x 2.4″ or 27.5 x 2.8″ tires. A medium sized ISO (50cm) has a claimed weight of 2400g complete with its axle, derailleur hanger, and all bolts & cable ports. The ISO comes in a wide size range and in two colors – gray or green.

Mason ISO bikepacking bike Availability, Spec & Pricing

Mason Cycles ISO 29er 27.5+ steel bikepacking adventure gravel dropbar mountain bike

The new Mason ISO will be available either alone as a frameset for £1495, or in one of two complete bike builds. A SRAM Force 1x Hydro complete bike will sell for £3500 and a Rival 1x Hydro complete will sell for £3195.

Both complete bikes share a Truvativ Stylo DUB crankset with a 34T chainring, Ritchey VentureMax Flare bars & stem, Mason seatpost, a Fabric Scoop saddle and either a new Mason x Hunt ‘The Search’ 29er wheelset with a dynamo of Hunt’s 27.5 TrailWide wheels wrapped in either WTB Ranger 29 X 2.4″ or 27.5 x 2.8″ tires.


    • Hi DeafDaddy,

      Thanks for your question.

      The extract from our press release below should help to answer it : ]

      Dom | Mason Cycles.

      “Our first bicycles, the Definition and Resolution were unflinchingly progressive, taking advantage of the latest thinking in tyres, hydraulic braking, wheel design and modern tubing. These bikes were designed as the ultimate Four-Season, mileage machines. Very soon, the Ultra-Endurance community realised that the comfortable, fast, multi-surface capabilities of these bicycles was ideal for the ContinentCrushing rides that they were undertaking, Josh Ibbett won the 2015 Trans Continental Race in record time on a Mason Definition and the #FastFar credentials of our bikes was firmly underlined.

      Then things progressed once again. Josh and riders like him wanted to ride fast, for a very long way but now they wanted to venture further off road. This was something more than ‘Gravel Riding’ and we responded by designing the multi award winning Mason Bokeh, this was the start of #AdventureSport and we now see riders strapping lightweight packs to these bikes and setting off on purposeful, fast, multi-terrain adventures, covering thousands of miles.

      This explosion in off-road, high mileage adventuring got us seriously fired up and we found ourselves taking the Bokeh to territory and terrain that we had never imagined riding with a bike like this. Josh found himself deep in the Mexican desert, fully loaded in deep sand. I found myself smashing down blue runs in the French Alps and linking runs together on isolated, steep, Rocky Mountain trails. The Bokeh handled this stuff incredibly well, it was amazing fun but it got us thinking again and after a long distance call from Josh [he was actually in his bivvy bag way out in the desert], I started sketching.

      This is how our radical new bike the ‘InSearchOf’ or ‘ISO’ was born. This new bike is still firmly in the #FastFar, #ContinentCrushing vein but a progressive new frame and fork design allow it to use 29 x 2.4” or 650b x 2.8 wheels, meaning steeper, rougher and deeper terrain are well within it’s capabilities. Multiple mounting points, a bespoke load-bearing mudguard, specific rack systems, 160/180 flat-mount braking and 100mm suspension-ready geometry mean that the InSearchOf, once again, does not shy away from the ‘Progressive’ word in our title.”

  1. So excited about this. A gravel bike for real dirt roads and trails.

    That single external cable is awful, though. Hope they can tuck it away for production. Not up to Mason’s usual aesthetic standards.

      • Hi Esteban LV, very true but we also find that sensible internal routing makes it much easier and more practical to strap packs on and helps keep the hoses/cables out of harms way. If you need to replace a hose or cable in an emergency you can always run it externally until you can re-route it properly. ‘Gnarly DH image’: This was a pic from when we were testing the p.types [we tested them hard] and it’s just a steep gravel bank really. This is the stuff we want it to take in it’s stride : ]

    • Hi Celest Greene, Great to hear you are excited about the ISO! The cable you are seeing is for the dropper post, it routes down the outside of the DT and then in through the base of the seat tube. So, you would only see this if you are running a dropper. It makes more sense to run it like this as it means a stronger DT with less holes in it! Many steel MTB brands also do it this way.

      Dom | Mason Cycles.

  2. Well…its nice and green, lightweight and features that push all the right buttons but the price for a frameset is a little out of my league…pitty.

  3. Sign me up! With a lockout-equipped front suspension fork something like this would be awesome for big mixed-terrain rides here in NM. $1600 or so is more than fair with a custom carbon fork, and a steal if it’s made in Italy like the rest of Mason’s line.

    If it’s anything like my Definition it’ll be a winner.

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