Gear News

Mason Definition2 road bike – first look

Mason's second generation, disc-equipped, aluminium road bike arrives for review

Back at the Cycle Show in September we spotted the second generation Mason Definition, a simply gorgeous machine which immediately had us negotiating with the Sussex-based brand to get a bike in for review on RCUK. And here it is.

You may be familiar with the Mason story; experienced bike designer Dom Mason founded the eponymous brand in 2015 and the aluminium Definition was part of the launch range, alongside the steel Resolution. The line-up has since expanded to include the Bokeh adventure bike (available in aluminium and titanium), but the Definition is the embodiment of the Mason ethos.

That is to say the Definition2 is a disc-specific, all-weather road bike, with generous tyre clearance and a geometry designed to offer both stability and speed. Let’s run through each of those points quickly.

Mason’s aluminium, year-round frame, the Definition2, has been updated to accommodate thru-axles and flat-mount disc brakes

The Definition was designed for disc brakes from the outset – the brand’s full name is Mason Progressive Cycles and discs are central to that forward-thinking philosophy. There’s not a rim brake in sight. Back in 2015, road disc brakes were still an emerging technology, with bike manufacturers yet to settle on a dropout standard, but thru-axles now rule the roost.

As a result, while the original Definition had quick-releases, you’ll see thru-axles and – also new – flat-mount disc brakes on the Definition2. “We hadn’t jumped onto the thru-axle/flat-mount bandwagon a year ago because we’d rather turn up late than do something average,” says Mason brand manager, Callum Nicklin.

In truth, the front end of the bike has been thru-axle for a while now, since Mason launched the Aperture2 fork, so the real work has gone into remodelling the rear.

“By working closely with the frame maker to develop our own machined thru-axle/flat-mount dropout, we’ve kept our signature ‘BoatTail’ shaped stays that contribute to the Definition’s excellent ride quality and unique rear triangle,” adds Nicklin.

Mason Definition2 road bike (Pic: George Scott/Factory Media)
Mason Definition2 road bike (Pic: George Scott/Factory Media)
Mason Definition2 road bike (Pic: George Scott/Factory Media)

That ‘BoatTail’ design sees the stays adopt a smooth bend to offer clearance for the disc caliper, rotor and, crucially, wide tyres, while also helping to meter out road buzz, according to Nicklin.

Tyre clearance is 33mm without mudguards and 30mm with (the Definition2 has discreet eyelets for full mudguards and a rack). That leads us neatly onto Definition’s geometry. Mason toyed with the idea of updating the geometry and when we initially spoke to Nicklin at the Cycle Show the plan was to shorten the chainstays by 5mm to give the frame a slightly more responsive ride.

However, that decision was reversed. While the Definition was initially designed around 28mm tyres a couple of years ago, Mason now regularly see customers speccing bikes with 30mm tyres and above, Nicklin says. Shortening the chainstays would have sacrificed that additional tyre clearance, he adds – something key to the Definition’s year-round persona.

As a result, the Definition2’s geometry remains identical to the original. The frame is available in six sizes, from 50cm to 60cm and our 54cm test bike has a 551mm effective toptube, 155mm headtube, 1010mm wheelbase, and 71.5 and 73.5 head and seattube angles respectively. It’s a geometry designed to give the bike a stability and predictability to tap out long, steady miles, while retaining a sense of speed and agility to liven up the ride. You can find the full geometry table on the Mason website.

The frame continues to be made from a custom Dedacciai tubeset, paired with a full carbon fibre fork. The toptube is ovalised to increase lateral stiffness by increasing the weld area at the headtube, according to Mason. The downtube is oversized, with a 48mm diameter, which apparently has allowed Mason to reduce the wall thickness without losing stiffness or sacrificing ride quality. That downtube feeds into a 50mm bottom bracket shell. The frame, meanwhile, is compatible with mechanical and electronic groupsets.

Neat design flourishes help the Definition2 stand out from the crowd

Otherwise, the Definition2 is typical Mason, with plenty of neat design flourishes across the frame – it’s very easy on the eye and is available in three colours (‘shutter black’, ‘lens blue’ and the ‘element grey’ finish of our test bike).

We’ve had the chance to take the Definition2 out for two short rides since it arrived, totaling just under three hours, and two things immediately stand out. First, the ride quality is sublime – it remains connected with the road while still offering feedback to the rider. Now, our test bike has plush 30mm Schwalbe G-One Speed tyres fitted to the Mason x Hunt 4Season Disc wheels so that will have a big impact, but it’s a positive start. We’ve also got a set of Hunt 50Carbon Aero Disc wheels to slot into the Definition2 and will wrap those in racier rubber to see how it responds.

Beyond the ride quality, the geometry is immediately likeable. I didn’t swing a leg over the original Definition but this second generation machine feels instantly familiar, like an old friend along for the ride. It has a reassuring stability while retaining a sense of agility when out of the saddle, with the bottom bracket providing a rigid and responsive focal point for the bike when climbing or pushing hard on the pedals. More riding will see how the Definition2 stands up to sterner tests.

We’ve touched on the spec but our Definition2 comes with a SRAM Rival 1 groupset and the American firm’s hydraulic disc brakes. The 46-tooth chainring is paired with an 11-42t chainring, giving a climbing gear slightly easier than a compact 34-tooth chainring with a 28-tooth sprocket. The carbon Mason-branded seatpost is topped with a Fabric Scoop saddle and the cockpit sports aluminium Deda Zero 1 finishing kit.

The Definition2 is available as a frameset for £1,150 or Mason offer the frameset in three builds, with Shimano 105 (£2,740), Shimano Ultegra (£3,130), Shimano Ultegra Di2 (£3,995) and Shimano Dura-Ace Di2 (£4.995).

That’s it for now, we’ll be logging more miles on the Definition2 over the weekend and the weeks to come. Full review to come on RCUK.

Website: Mason Progressive Cycles

Something for the weekend showcases our pick of the latest tech to arrive at RoadCyclingUK. You can see more here.


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