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Mason Definition road bike



Production bike with bespoke feel and wonderful, inspiring, addictive ride

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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Brighton based Mason Cycles has let us loose with one half of its initial line up, the Definition. It's a four season long distance machine with the manners of a tourer and the temperament of race bike.

It's good. So bloody good it's been difficult trying to get into words just how a handful of alloy sticks welded together can leave you feeling so excited. You don't get a ride governed by angles and dimensions here; the Definition seems to mutate as the speed/gradient/direction changes leaving you wondering if you are still riding the same bike you were five minutes ago.

Sorted geometry equals sublime handling

With a wheelbase of 1010mm, room for full mudguards with 28mm tyres and a relaxed looking front end you'd be excused for thinking the Definition is some sort of audax-style winter trainer. What you get though is a frame that's mild mannered and easy to ride whether it's doing 16 or 60mph (okay 56.9mph, bloody HGV limiters) in the wet or dry.

The key to a good mile muncher is that you don't notice it. If you've tapped out a steady hundred miles and not once thought about the bike it's doing its job. The Definition can do this, miles and miles can go by and the bike will just roll on with little input through the steering.

But we all need a little bit of excitement in our lives and when you give the pedals a kick those Dedacciai tubes deliver a ride to challenge most race bikes.

As the bends start to tighten and the speed increases the tapered head tube and steerer combination comes into its own giving a sharpness and directness to the steering. Handling like its on rails may be a cliché but is totally apt here; point the handlebars at the line you want and the Definition nails it without compromise.

The bottom bracket height has been dropped a touch to counteract the larger volume tyres and alongside that meter long wheelbase the whole bike remains stable at high speed or under heavy braking. A rough road surface won't upset it either.

I thought I'd over-cooked it a couple of times entering roundabouts or bends on a country lane but the Definition just keeps leaning and holding that tight line. A squeeze of the hydraulic disc brakes just tightens the arc a touch if you need to without an unwelcome shift of body weight.

Long rides often see you travelling unfamiliar roads. The knowledge and confidence that the bike will get you out of a tricky situation is a nice feeling to have especially if the fatigue is kicking in and increasing the chances of you making a mistake.

It's not just how precisely it responds in the bends that makes the Definition so rewarding to ride, it's the fact that you can ride it however you are feeling at that particular time. Go steady or go eyeballs out and you'll get the same level of feedback and control.

The Aperture fork is designed specifically for Mason's two bikes, the Definition and the Resolution, and it's a beauty. The carbon layup means you get no chatter from the road surface even at extreme lean angles, despite the stiffness of the legs. It also provides perfect resistance to massive braking efforts.

Stiffness without harshness

Aluminium alloy frames have always had a reputation for being harsh but alloy tubing has had some real investment and technological advances over the last few years. Those tubes build into creating stiff frames without the bone shaking characteristics.

The Dedacciai tube set used on the Definition is testament to this, offering a beautifully smooth ride that shows hints of an almost steel like softness while retaining the stiff undertones of the 7000 series, T6 heat treated alloy.

Mason Cycles' eponymous designer and head honcho Dom Mason handpicked the tube set himself rather than just use an off the shelf selection to create the exact ride feel he was after both in terms of performance and comfort. As with the handling, this is apparent when the bike is being ridden at differing efforts.

Spinning it along easily it rides through the bumps absorbing the majority of the road buzz even with the tyres pumped up to 120psi. You can feel the stiffness of the frame through the pedals being linked to the meaty bottom bracket junction but up near your hands, at the top tube/head tube junction, things are a lot calmer. The feel is ever so slightly different, softer even.

The seatstays are curved which tames the rear end under hard acceleration and dulls the resonation of the road travelling up to the rider before it can reach the saddle.

When the red mist descends though the whole bike again feels like it transforms into a tighter, more nimble beast. The power goes through the down tube and bottom bracket without any feeling of loss as the Definition surges forward. It's not exactly a sprinter but the change of pace is instant and above all addictive, like it's goading you to push that little bit harder than you really need to.

This is true as well when you are in the hills. That bottom bracket area makes sure all of your effort goes to the rear wheel whether you're climbing seated or honking hard on the bars for the really steep bits. At 8.6kg (18.95lb) for this build the Definition climbs well. The Mason x Hunt 4Season wheels' low weight is really noticeable here compared to other disc wheels currently available.

On a 200km ride to Brighton to drop the Definition back to Mason HQ I stepped off the bike without a single ache or pain. Arms, wrists and neck are the usual places I suffer once I get past four or five hours on a stiff bike, but those aches and pains didn't appear. In fact I was fresh enough to ride back the next day on the steel Resolution.

Attention to detail

I'd still be a bike fanatic even if I didn't cycle. I just love the way a road bike looks especially metal ones with tubes and things which is why the Definition gives me such a buzz.

The curved seat and chain stays are a work of art as well as being functional. The longer wheelbase allows for plenty of heel clearance on the chain stays too considering the extra width of a disc hub.

The quality of the finish on the Definition is second to none, from the welding through to the paint and decals. To achieve this Mason has the frames shipped around Italy to the companies he has handpicked for the quality of their work. The photos just can't do the finish justice; it really needs to be seen in the flesh and preferably in the sun.

The welding is neat and tidy and thankfully left in its raw state. I prefer to see the joins rather than sanded for a smooth finish, it keeps the bike's engineered look and means there is no chance of the tube wall thickness being reduced through over-zealous sanding.

Mason offers a five year guarantee on the frame and fork plus two years on Mason components; that's an impressive testament to his confidence in its quality.

It's the little details that bring a completeness to the frame though, things like the MultiPort system that allows you use various nodules and blanking plates depending on which groupset you are running internally through the frame – electronic or mechanical. The positioning of these entry and exit points provide smooth cable rums for unrestricted shifting quality if you are running cables, removing tight bends and keeping things close to the frame and avoiding moisture collecting sumps. The MultiPorts used on the 48mm diameter downtube are staggered to create this kind of detail.

Continuing this tidy run is the unique thruBB bottom bracket shell which is oversized at 50mm diameter before stepping down to accept standard threaded BB cups. This allows clearance to run the cables and brake hose through the BB shell without the risk of pinching or restricting function plus a larger surface area for welding.

As I mentioned above the Definition frame is fully equipped with bosses for full mudguards and a rear rack and a few more discretely situated on the wheel side of the seatstays for tidy cable routing. Fittings are positioned underneath the redundant rear brake bridge and on the chain stay bridge too.

This level of detailing continues to the fork as well. Like I said earlier the fork has been completely designed by Mason to work with this frame. Perfecting the height, clearance and ride quality has allowed him to refine everything else too, like the internal cable/hose routing for the disc caliper and placing the mudguard bosses on the inside of the fork legs for a minimal look. The Aperture has traditional dropouts rather than a thru axle which is a sensible option at the moment while (if) the industry decides on a standard.

The full carbon steerer has an even taper, unlike some that are just straight down to a small section of larger diameter at the bottom. The Aperture steerer therefore has a larger surface area for stiffness.

Well specced finishing kit

The Definition is available in four build options plus a special order Dura-Ace Di2 so the Ultegra Di2 version we've got is the top off the shelf spec. You get the new hydro shifters to work with the Shimano hydraulic disc brakes and it's a match made in heaven. Being able to brake and change gear at the same time in total control is a massive confidence booster and you don't realise how much of a benefit it is until you switch back to mechanical.

It's a full groupset too with chainset and both mechs adding to that complete look you get when all of the components match. The shifting on Di2 has got much smoother over time and although the front mech is still on the large side the rear looks very little different from the mechanical version.

The braking from the latest generation Shimano hydraulics is phenomenal. The control from the levers is class-leading and while you can easily lock the rear wheel you soon get used to how much power you need to use.

The style of the braking perfectly matches the mannerisms of the Definition, aggressive and pin point accuracy when you want it, gentle inputs when you don't.

Running with the Italian theme the headset, handlebars and stem are all Deda items. The spec level increases with the build option/groupset you go for and on our model the upper level alloy components of the range suit the frame perfectly. They are stiff but thanks to slight shock absorbance of the frame not overly so.

The majority of the Deda bars have a shallow drop these days so they suit a larger selection of hand sizes and are very comfortable to ride. Descending in the drops is a real pleasure, being able to spread your weight out over the bike.

All the bikes and frames are shipped with a Mason seatpost made from UD carbon fibre. It's 27.2mm in diameter to allow some flex between frame and saddle. It's easy to set up for fore and aft or levelling the saddle.

Fabric provides both the saddle and bar tape and they're really good stuff. The Scoop saddle has a decent mix of stiffness and padding and is very supportive over long distances. The bike swap weekend I put in over fifteen hours on the bike and while I knew I'd done a big weekend I suffered no numbness or chafing at all from the saddle.

The tape is wipe clean which is a really huge bonus if you're running white like our test model was, that'll save you a few quid over the course of the year. The rubbery feel gives plenty of grip and a reasonable amount of padding though I did get the odd tingly finger if I wasn't wearing gloves.

Wheely, wheely good

Mason have gone down a collaboration route for the wheelset on the Definition with fledgling brand Hunt to create the 4seasons, and attention to detail is the defining factor here too.

The 27mm deep rims use a 23mm wide rim (17mm internal) which suits the profile of the 28mm wide Continental Grand Prix All Season tyres perfectly. The width increases grip and ride quality, and gives a little bit in the way of an aerodynamic boost too. They are tubeless ready if that takes your fancy.

They use a quality selection of components from the likes of EZO bearings from Japan and Pillar spokes with reinforced heads. This allows for a strong wheelset to be handbuilt without a weight penalty, they are a claimed 1585g. They roll smoothly and stayed true throughout the test period and are continuing to on the Resolution review bike so longevity isn't going to be an issue.

Additions like stainless hardwear on the skewers is a decent insight especially for a bike that is likely to be used in all weathers.

They are priced at £349 so absorb a decent chunk of the budget but it's where you want your money to go. We see lots of bikes of similar prices being let down by low-priced heavyweight wheels.

The Conti tyres offer really decent grip especially in the dry. They are surefooted and thanks to the profile allowed by the wheels you can really bank them over in the bends. Their resistance to cuts and punctures is second to none as well.

Defining the Definition

You can probably tell by the length of the review that the Mason Definition has tremendous depth to it with regards to the ride, the overall finish and detailing. It's a production bike but with that kind of custom finish to it.

The ride is amazing, pure and simple. The tubes, the geometry, the finishing kit all come together to create a package that is hard to fault. The way it seems to come alive as you put more and more effort into becomes like a drug to the point where I was rarely taking it steady anymore. I needed that hit.

The finish and the way it looks on the road just adds to the pleasure. I love the way the Mason logo faces you on the down tube and I think it tops the table with regards to head tube badges.

Overall the Definition manages to be an all-rounder without displaying any compromises.

Full details of specs and geometry can be found on


Production bike with bespoke feel and wonderful, inspiring, addictive ride

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Make and model: Mason Definition

Size tested: 54

About the bike

State the frame and fork material and method of construction. List the components used to build up the bike.

Frame: Dedacciai 7000 T6 series aluminium alloy

Fork: Full carbon disk, tapered steerer

Headset: FSA Tapered

Handlebars: Deda

Stem: Deda

Seatpost: Mason carbon fibre

Saddle: Fabric Scoop

Shifters: Shimano R785 Di2 11spd Hydraulic

Chainset: Shimano Ultegra 50-34

Front Mech: Shimano Ultegra Di2

Rear Mech: Shimano Ultegra Di2

Brakeset: Shimano BR-R785 Hydraulic (140mm Rotors)

Wheelset: Mason x Hunt 4Season

Tyres: Continental 4 Season 700x28

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?

The Definition is described by Mason as a long distance machine that still delivers a quick and entertaining ride with the added benefit of being able to take guards. I think the Definition delivers exactly that.

Frame and fork

Overall rating for frame and fork

Tell us about the build quality and finish of the frame and fork?

The attention to detail, the finish, the welding - there isn't a fault to be found anywhere on the frame or fork. A lot of thought has gone into the frame, that is evident just by spending five minutes looking it over.

Tell us about the materials used in the frame and fork?

The frameset is handbuilt in Italy out of Dedacciai's 7000 series alloy which has been heat-treated to T6 grade for added strength. The tubing is triple butted for weight saving and ride quality.

The fork is made in Taiwan and designed by Mason. It includes a full carbon tapered steerer and internal hose/cable routing for the disc brakes.

Tell us about the geometry of the frame and fork?

At first glance the front end looks very relaxed with the 71.5 degree head angle but as a complete package the Definition delivers on stability and precision.

Full details here -

How was the bike in terms of height and reach? How did it compare to other bikes of the same stated size?

Mason says that he's concentrated on height and reach rather than just tube lengths to deliver a better geometry. The height of 565.3mm and reach of 388.3 on our 54cm test frame provided a very comfortable position being just stretched out enough to get a decent 'fast' tuck for plenty of miles pain free.

Riding the bike

Was the bike comfortable to ride? Tell us how you felt about the ride quality.

Yes, the Dedacciai tubing doesn't suffer from harshness at all making the Definition a pleasure to ride for long distances.

Did the bike feel stiff in the right places? Did any part of the bike feel too stiff or too flexible?

It is a very good balance, stiffness around the BB is very high with other places on the frame allowing some give to maintain comfort.

How did the bike transfer power? Did it feel efficient?

Very well, the Definition seems to enjoy being pushed hard and delivers power straight to the road.

Was there any toe-clip overlap with the front wheel? If so, was it a problem?

No, it shouldn't be an issue with guards either. The geometry is designed to eliminate this.

How would you describe the steering? Was it lively, neutral or unresponsive? Neutral handling for those long miles though lively enough to excite in the bends.

Tell us some more about the handling. How did the bike feel overall? Did it do particular things well or badly?

The front end geometry and long wheelbase means the Definition is very stable and holds a line very well indeed.

Which components had the most effect (good or bad) on the bike's comfort? would you recommend any changes?

The Fabric Scoop saddle is very pleasurable and feels worn in straight away. Being able to use large volume tubeless tyres means you can drop the pressure for added comfort too.

Which components had the most effect (good or bad) on the bike's stiffness? would you recommend any changes?

Deda's alloy bar and stem combos have always been stiff and nothing changes here.

Which components had the most effect (good or bad) on the bike's efficiency? would you recommend any changes?

The Hunt wheels are light for disc wheels and really bring a lot to the overall ride. I've ridden plenty of big money disc equipped bikes that are let down by cheap, heavy wheels so it's good to not see that happening here.

Rate the bike for efficiency of power transfer:
Rate the bike for acceleration:
Rate the bike for sprinting:
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The drivetrain

Rate the drivetrain for performance:
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Tell us some more about the drivetrain. Anything you particularly did or didn't like? Any components which didn't work well together?

The Ultegra/hydro set up used on our test bike is lovely. The shifting has got better compared to the first generations but best of all is how well the shifters work with the hydraulic brakes, being able to brake late and change gears at the same time is great on unfamiliar roads.

Wheels and tyres

Rate the wheels and tyres for performance:
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Tell us some more about the wheels and tyres.Did they work well in the conditions you encountered? Would you change the wheels or tyres? If so, what for?

The Mason x Hunt wheels are befitting of the bike. The finish and build quality is top notch plus using quality components means weight can be trimmed without affecting durability.


Rate the controls for performance:
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Tell us some more about the controls. Any particularly good or bad components? How would the controls work for larger or smaller riders?

The compact Deda bars provide plenty of positions and are stiff enough for high speed direction changes while providing a decent level of comfort.

Anything else you want to say about the componentry? Comment on any other components (good or bad)

The new Fabric range seems to be delivering performance on a sensible budget and if the Scoop is anything to go by we should be seeing a lot more of them. Their bar tape is comfortable and properly wipe clean, ideal for white tape lovers.

Your summary

Did you enjoy riding the bike? Yes.

Would you consider buying the bike? Yes.

Would you recommend the bike to a friend? Yes.

Rate the bike overall for performance:
Rate the bike overall for value:

Anything further to say about the bike in conclusion?

The Definition sums up to me exactly what I think cycling is all about. It's not just about price, weight or components, it's about the whole package. Delivering a ride that thrills though relaxes too and every time you look down and see that deep paintjob in the sun it makes you glad you went out. It makes you feel special like you haven't got a care in the world.

Overall rating: 9/10

About the tester

Age: 36  Height: 180cm  Weight: 76kg

I usually ride: Kinesis T2  My best bike is: Kinesis Aithien

I've been riding for: 10-20 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 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!

Latest Comments

  • chrisonatrike 0 sec ago

    Off to a dictionary with you!  Not that it matters, people choose their own definitions....

  • hirsute 19 min 8 sec ago

    I was not suggesting that they should get radar merely pointing out how radar can be useful. There was a recent review of a radar unit on here...

  • BalladOfStruth 43 min 22 sec ago

    There's something I don't miss from the morning commute - an Audi A3 overtaking me within spitting distance of a junction, hard on the brakes as it...

  • BalladOfStruth 47 min 42 sec ago

    I think it might actually be the least popular behaviour in all of web design.

  • lesterama 49 min 40 sec ago

    Here's some hope for us chunky blokes, even if most of won't consider spending £3.5k on wheels.

  • Rezis 51 min 13 sec ago

    If running it poorly affected their salaries and bonuses (and other accountabilities) maybe they would run it properly......

  • simonmb 1 hour 2 min ago

    Passing a cyclist in the opposite direction warrants at least a nod or a gentle lift of the hand from the bars. But what about overtaking a fellow...

  • brooksby 1 hour 57 min ago

    If a bicycle is the only vehicle stopped at a zebra crossing, you should just go around them.

  • Secret_squirrel 2 hours 28 min ago

    Im considering something like this to replace my current storage bottle on my downtube.  It does the job of keeping the tools safe and dry but at...

  • brooksby 12 hours 10 min ago

    The wheelbenders were on the verge again, so since there were no other bikes in sight i locked mine along the back of them....