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The Mason Definition Chorus is a jack of all trades, yet amazingly a master of all. It's the definitive all-round road bike, one that offers great ride quality and geometry that works both at speed or when cruising along – and that's whether you're crossing town, the county, or even the country. The build quality and finish are flawless too.
Back in 2015 I felt that Mason's Definition was the pinnacle of what an aluminium alloy road bike could be, and one that was breaking boundaries, too.
While we may now see performance road machines with tyres wider than 25mm – and running disc brakes only – as the norm these days, by 2015 standards it was quite a leap of faith.
The fact it had geometry you could ride all day, quickly and in comfort, also blurred the lines between the endurance and race machine pigeon holes. It could even take mudguards, too.
It's had a few tweaks over the years, but thankfully Mason has generally taken the 'if it ain't broke, don't fix it' route. The original Definition used QR skewers front and rear, for instance – though only because designer Dom Mason was waiting for thru-axle standards to settle down – before being updated to 12mm thru axles.
Other than that though, very little has changed. While it's actually quite rare for us to revisit a bike that hasn't seriously changed since the last time we rode it, the times themselves have changed. When we were offered the Definition Chorus, I was intrigued to see how it had stood the test of time.
With all of the advances in aluminium tubing, and seven years of the competition watching and learning, would it still cut the mustard?
The answer is yes!
For my first ride on this Definition, I rolled out of the estate and hit the back lanes, and straight away I was in a happy place. That original Definition has remained in my memory as having possibly the best ride quality of any aluminium alloy frame out there – the talk of aluminium frames giving a harsh ride has been silenced over the years, and the Definition is one of the reasons why.
It doesn't behave in a way many alloy bikes do, it's so damn comfortable. The way it silences road buzz is more like titanium or steel, giving off a velvety feel, a softening around the edges if you like, and without ever minimizing any of the feeling of integration between rider and bike.
And that's the thing: the key to the Definition is that it truly feels like an extension of you.
It feels so poised on the road, even when the surface is rough (as they so often are), and the lack of 'buzz' leaves the Definition feeling planted. That in turn gives an extra boost of confidence for you to push it hard in the bends.
The geometry is spot on too, with a balance of angles and tube lengths that sits towards the endurance end of the market. The front end isn't as razor sharp as the raciest of race bikes, but it's very close, and the slightly slacker head angle – plus a wheelbase a few millimeters longer to accept full mudguards – means handling that's a little bit less frantic. It really allows you to ride the Mason quickly over long distances.
I've hit over 50mph many times on the Definition, and it feels exceptionally solid there, flowing through the bends sweetly. It's easy to hit the apex on even the most technical of descents.
The head tube is relatively short which helps you get tucked into the drops to lower your centre of gravity, although it isn't so short the saddle to bar drop becomes extreme.
There is no issue with any fork flex when banked over hard or scrubbing speed off before a turn, and the fork legs' stiffness gives positive feedback from top to bottom. It's a front end that lets you know exactly what the tyre is up to.
The frame also is impressively stiff, which makes the Definition feel nimble and responsive on the climbs. It's no lightweight whippet, but considering its intentions it's no slouch when ascending – either in the saddle or when dancing on those pedals.
It's the same on the flat. The Mason is well suited to tapping out the miles at a decent pace, but should the need arise for a hard effort or a touch of sprinting, you won't be left disappointed.
From a ride point of view the Mason is just a beautiful place to be. It's such a capable piece of design that it always feels like the right bike for the job (well, probably not if you find yourself on the start line of a crit, but you know what I mean) regardless of your pace or aims for that particular ride.
The ride quality is excellent, but this is where the Definition really shines. I've met Dom Mason countless times over the years and the one thing I've learnt is that he is a stickler for the details. That's highlighted when you get up close to the Definition.
The frame is handbuilt in Italy using triple-butted 7000 series aluminium tubing made by Dedacciai, custom drawn to the exact shape and wall thicknesses specified by Mason. It's this shaping that has the largest impact on the overall ride quality, rather than just the material itself.
The Definition uses sizes and shapes ranging from the beefy 1 1/8in to 1.5in tapered head tube and large D-section down tube, down to a slender, ovalized top tube. The rear triangle incorporates what Mason call its BoatTail stays.
The seat stays taper as they curve towards the dropouts, with the chainstays curving up to meet them. The custom bending creates rotor and caliper clearance, helps reduce chain slap and allows for some comfort-enhancing compliance, according to Mason's website.
As before this uses a threaded bottom bracket, although the diameter of the shell is larger than most at 56mm. That gives more room to run the gear cables, wires and brake hose under the BB sleeve. It also gives a larger weld area at the down tube for maximum strength and stiffness. The shell is then 'stepped down' to accept the bearing cups of a standard threaded 68mm-wide bottom bracket.
All the cables, wires and hoses are run internally using Mason's Multiport system, which provides various 'plates' to accept whichever of those three you are inserting or extracting from the frame.
The entry ports are on the down tube, with the front mech cable/wire exiting at the rear of the bottom bracket shell, while the brake hose and rear mech cable/wire leave the corresponding chainstay. There's internal routing for a dynamo wire, too.
The welding throughout is exceptional; a real work of art, with the frame and fork finished in a deep luxurious paint job in either the Lens Blue found here, Shutter Black, or Vela.
The Aperture2 fork is unique to Mason, and weighs in at 365g. Wheel retention is taken care of by thru-axles, and Mason's F-Stop system allows for the axle inserts to be replaced should the thread ever get damaged.
The mudguard eyelets are discretely placed on the inside of the legs, which means the stays will need a little bit of fettling before fitting the guards, though that's a straightforward process (I'm speaking from experience).
Tyre clearance is 32mm with mudguards and 35mm without, although this depends ultimately on your tyre and wheel combination.
The Definition is available in eight sizes, which is an impressive number given the relatively small scale of production. The smallest frame is a 48cm, and the largest is a 62cm with 519mm and 601mm effective top tube lengths respectively.
This one is a 54cm with a 551.5mm effective top tube, a 155mm head tube, and a 1,009mm wheelbase. Angle-wise the head is 71.5°, and the seat tube is 73.5°. If you base sizing on stack and reach, on this size frame you're looking at 565.5mm and 383mm respectively.
Mason offers a detailed geometry table on its website for all sizes, and a page on sizing advice based on various bike models.
The Definition line up is available in a range of builds, with SRAM, Shimano and Campagnolo offering both electronic and mechanical shifting, and even 1x in the case of Campag's Ekar. There is also a 'rolling chassis' option including frameset and wheels, plus a frameset-only option.
We have the Campagnolo Chorus option, and very impressive it is too. The builds we get in for testing are most commonly running groupsets from Shimano, with most of the rest wearing SRAM. Unfortunately very few come in with Campagnolo, although that has changed somewhat of late – the Italian manufacturers haven't suffered the same supply and availability issues as the others.
Back when I started riding in 2000, SRAM was yet to enter the road groupset market, so a few small component manufacturers aside you were either a Shimano or a Campagnolo rider. There was much banter from 'experts' on either side of the club run. The main truism I can remember was that 'Shimano wears out, while Campag wears in.'
I've since run groupsets from both brands to the end of their lives, and I'd say they are actually pretty equal, but I get where the saying comes from. Campag's shifters do take a while to bed in, and that's noticeable here too. Straight out of the box, Chorus shifts don't feel quite as smooth and refined as, say, Shimano's Ultegra; each takes a bit more pressure at the lever, and there is more of a clunk as the chain drops or climbs a sprocket.
That doesn't last for long though: 500-1000 miles later and the shifting really starts to come into its own, requiring less of a press to activate. I like the defined click from the Chorus shifters too – you definitely know the chain has moved without having to glance around – plus the hoods and the curved carbon brake levers just fit so well with the natural resting positions of your fingers.
You can also carry out multiple shifts at once, up or down the cassette.
The carbon crank arms suit the high quality of the Definition's finish, and Campag offers chainrings in all the standard sizes including 52/36t (the largest the Definition can accommodate), 50/34t and a 'gravelesque' 48/32t. There is a range of 12-speed cassette options too, so you can spec your Mason up with the gearing that best suits you.
Campag was late to the game with hydraulic disc brakes, but they were definitely worth the wait. There is loads of power on tap, requiring just two fingers on the levers, and I braked from some very high speeds without issue even on the hoods. As with the majority of hydraulic calipers on the market, modulation is great wet or dry, and if you manage to lock the front wheel up you are doing something wrong.
As for the rest of the kit, Mason likes to keep things as Italian as they can be. Both the stem and handlebar are Zero2 offerings from Deda's catalogue, and the saddle is Fizik's Tempo R3.
The seatpost is Mason's own carbon fibre Pento model in a 27.2mm diameter.
It's all good quality kit, and there is certainly nothing you'd need to head out and upgrade.
Mason has long associated with Hunt Wheels, the pair having collaborated on the wheelset for the original Definition and Resolution.
So it's no surprise to see a Mason X Hunt 4Season V2 alloy disc wheelset here as standard. Other options are available though, and ours has an upgrade to a set of Hunt's carbon wheels.
The wheels performed faultlessly throughout testing and the ride quality is excellent, while the 35mm deep rim brings a tiny bit of aeroness to proceedings and drops a bit of weight.
Our wheels were wrapped in Schwalbe's very capable Pro Ones in a 30mm width. The Pro Ones are grippy in all kinds of conditions and roll excellently. I've used them on lots of test bikes and have always been pleased with them. Durability is decent too, especially considering they are a performance tyre.
The range starts at £3,045 for mechanical Shimano 105, with the £3,225 mechanical Ultegra build coming next. The Ekar model is £3,600 and this Chorus version is £3,665 with the standard wheels.
Above that Mason switches mechanical groupsets for electronic, with the new 105 Di2 offering being the cheapest at £3,595. Ultegra Di2 comes in at £4,145, while SRAM's Rival AXS is £3,695 and the top-flight Red AXS rings the till at £6,045.
A frameset will set you back £1,375.
When it comes to the competition it's amazing how few brands have high-end aluminum bikes in their lineup. The big brands are almost exclusively carbon fibre, and the custom builders – or other small batch producers – tend to focus on steel or titanium. Personally, I think that is a shame as aluminium has a lot to offer.
So, let's have a look at the alternatives regardless of frame material. Giant's Defy Advanced Pro 3 has the same tyre clearance as the Definition, and it's designed for the same sort of riding style. 'Endurance Road' Giant calls the geometry, and I found its carbon frameset a very comfortable ride.
It's only a few hundred grams lighter than the Mason but comes with the bonus of deep-section carbon wheels. With a mechanical 105 groupset it costs £2,999 (down from £3,299 in 2021) which is £46 cheaper than the equivalent Definition. That's quite a small margin considering it's mass-produced, versus the small-scale production of the Mason.
Condor's Fratello Disc is made from Columbus' Spirit steel tubing, so it's probably more of a direct comparison to Mason's Resolution, and it's handmade in Italy, has mounts for mudguards and will also take a rear rack.
I absolutely loved the ride quality back in 2020, and it's a looker too. The skinny tubing means the cable routing is external though, so it isn't quite as clean-looking at the Mason offerings. It's available as a frameset and costs £1,299.99 in 2022.
I reckon such comparisons show the Definition is good value for money, and the price is easily justifiable when you see the extreme quality in the flesh. The Definition is as close as you can get to a custom, yet off the shelf, bike.
Phenomenal – that's the only word I can really think of to describe the Definition as a package. Just looking at the build quality and impeccable paint finish, I could easily forgive the Mason if it rode like a garden gate. Thankfully though, it doesn't. The ride is sublime.
Back in 2015 I said I couldn't understand how a handful of alloy sticks welded together could leave you so excited, and I stand by that seven years later. Aluminium alloy still has so much to offer, and the Definition is its showcase.
The way this thing rides is a masterclass in bike design and engineering
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road.cc test report
Make and model: Mason Definition Chorus
Size tested: 54
About the bike
List the components used to build up the bike.
Shifting: Campagnolo Chorus 12spd. Ergopower
Chainset: Campagnolo Chorus 12spd. Ultra Torque
Cassette: Campagnolo Chorus 12spd.
Chain: Campagnolo Chorus 12spd.
Braking: Campagnolo Chorus Hydraulic Disc
Tyres: Schwalbe G-One 30mm / Pro-One 28mm. Others available.
Wheels: MASON x HUNT 4Season V2 disc wheels. Other options available.
Handlebar: DEDA Zero2 black on black. 295g.
Clamp: MASON Macro alloy ultralight.
Seatpost: MASON Penta carbon, microadjust.
Saddle: Fizik Tempo Argo R3
Bar Tape: Mason Contact Tape.
Stem: DEDA ZER02 black on black. 140g.
Tell us what the bike is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about the bike?
Mason say, "Our Italian made, Dedacciai tubed, aluminium all-road bicycle that tackles the most variable and unpredictable surfaces with confidence and poise. The Definition is designed to deliver sporty, long-distance performance in the harshest conditions."
The Definition is indeed a versatile machine, with excellent handling and ride quality for covering big miles at speed.
Where does this model sit in the range? Tell us briefly about the cheaper options and the more expensive options
This model sits around midway in the line up. I've listed the various models and prices in the value section of the main review.
Frame and fork
Tell us about the build quality and finish of the frame and fork?
The attention to detail is excellent, including the high quality welding and flawless paint job.
Tell us about the materials used in the frame and fork?
"Dedacciai, custom formed, triple-butted performance Aluminium frame with Mason Aperture2 full carbon Thru-Axle/Flat-Mount fork."
Tell us about the geometry of the frame and fork?
The geometry is more relaxed than a traditional race bike with a slacker front end and slightly longer wheelbase for stability (and to accept full mudguards). It still provides a performance ride, though.
How was the bike in terms of height and reach? How did it compare to other bikes of the same stated size?
The stack and reach figures create a 'sporty' position without being as extreme as a full race bike. In relation to the frame size, there are no big surprises in terms of those stack and reach numbers.
Riding the bike
Was the bike comfortable to ride? Tell us how you felt about the ride quality.
Very comfortable. The Dedacciai tubing gives an excellent ride quality.
Did the bike feel stiff in the right places? Did any part of the bike feel too stiff or too flexible?
Stiffness levels are very impressive where they need to be, most notably at the front end and around the bottom bracket.
How did the bike transfer power? Did it feel efficient?
The Definition feels very efficient, and behaves like a much lighter bike.
Was there any toe-clip overlap with the front wheel? If so was it a problem?
No issues with overlap.
How would you describe the steering? Was it lively neutral or unresponsive? Biased towards neutrality, but with enough speed for the handling to be fun and involving.
Tell us some more about the handling. How did the bike feel overall? Did it do particular things well or badly?
The Definition is an easy bike to ride fast thanks to positive handling and great feedback.
Which components had the most effect (good or bad) on the bike's comfort? would you recommend any changes?
I got on well with the Fizik saddle, and the other contact points offer a comfortable position.
Which components had the most effect (good or bad) on the bike's stiffness? would you recommend any changes?
Campagnolo's Chorus crankset offers great stiffness when putting the power down.
Which components had the most effect (good or bad) on the bike's efficiency? would you recommend any changes?
The impressive grip of the Schwalbe tyres allows you to push hard into the bends without scrubbing off much speed.
Tell us some more about the drivetrain. Anything you particularly did or didn't like? Any components which didn't work well together?
Campag's Chorus is a lovely groupset to use, with the highlight being the comfortable shapes of the hoods and brake levers.
Wheels and tyres
Tell us some more about the wheels.Did they work well in the conditions you encountered? Would you change the wheels? If so what for?
The upgraded carbon Hunt wheels on this model performed excellently throughout the test. They're highly durable and light too.
Tell us some more about the tyres. Did they work well in the conditions you encountered? Would you change the tyres? If so what for?
Good quality tyres with plenty of grip, and minimal rolling resistance.
Tell us some more about the controls. Any particularly good or bad components? How would the controls work for larger or smaller riders?
The Definition comes with good quality componentry for the price.
Did you enjoy riding the bike? Yes
Would you consider buying the bike? Yes
Would you recommend the bike to a friend? Yes
How does the price compare to that of similar bikes in the market, including ones recently tested on road.cc?
There aren't many high-end, small-batch aluminium frames on the market – many brands prefer to focus on steel, carbon and titanium. I have mentioned a few alternatives in the main review, though.
Use this box to explain your overall score
The Defintion is an investment, but the high quality of the frame and fork means it's an investment worth making. The whole bike looks amazing, and the looks are backed up by a brilliant ride quality.
About the tester
I usually ride: This month's test bike My best bike is: B'Twin Ultra CF draped in the latest bling test components
I've been riding for: Over 20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: time trialling, commuting, club rides, sportives, fixed/singlespeed,
With 20 years of road cycling and over 150,000 miles in his legs it's safe to say Stu is happiest when on the bike whatever the weather. Since writing his first review for road.cc back in 2009 he has also had a career in engineering including 3D-CAD design and product development, so has a real passion for all of the latest technology coming through in the industry but is also a sucker for a classic steel frame, skinny tyres, rim brakes and a damn good paintjob.
His fascination with gravel bikes is getting out of control too!