Reviewed by Jess Pedersen and John Hauer // Photos by Shawn Spomer and Lear Miller
Inspired by the aggressive Mason 29er hardtail, Diamondback's 140mm Mason FS entry into the mid to long-travel full suspension 29er trail bike market serves up a rowdy looking package. Curious to see how recent improvements to the suspension and frame design played out, we pointed the Mason FS up and down some of the rowdiest trails in Sedona, Arizona during the 2014 Vital MTB Test Sessions.
Mason FS Pro Highlights
- 6061-T6 weapons grade aluminum frame
- 29-inch wheels
- 5.5-inches (140mm) of rear wheel travel
- Knuckle Box suspension
- Tapered headtube
- 66.5-degree head angle
- 73-degree seat tube angle
- 13.6-inch (345mm) bottom bracket height
- 18.3-inch (464mm) chainstays
- Threaded bottom bracket shell with ISCG mounts
- 142x12mm rear through axle
- Measured weight (size Large, no pedals): 32.0 pounds (14.51kg)
- $6,000 MSRP
Early Vital MTB readers surely remember the advertisement featuring a monster truck announcer’s voice screaming “KNUCKLE BOX!” before practically every video. While it may have seemed a little corny, Diamondback’s four-bar suspension technology has some true potential that is worth screaming about. This design deserves more attention than it gets.
Also known as a bell crank, the Knuckle Box serves as the center of the single-pivot four-bar suspension platform and redirects bump forces from the seat stays to the shock. The progressive design keeps the majority of the weight low and centered, which helps out a bit in turns and with stability. A custom tuned FOX CTD Float rear shock compliments bike, offers a good platform when the trail heads uphill, and is easy to reach on the fly. All 14 Enduro Max bearings needed to keep the system running smoothly can be easily accessed thanks to the oversized, single-sided aluminum hardware that rounds out the Mason FS.
Perhaps the most important story about the Mason FS is how Diamondback has improved lateral stiffness in the rear end. During last year’s Vital Test Sessions, we faulted the similarly designed Diamondback Sortie 3 29er with stiffness issues, so it was refreshing to see the company take a few steps in the right direction by beefing up the rear end. New with the Mason FS, the bell crank has been anchored to a pivot that goes through the downtube rather than on top of it, gaining width and increasing stiffness. The seatstay bridge was also beefed up significantly, though this came at the expense of increased chainstay length. The chainstays are also visibly larger and have a more symmetric design. A 142x12mm axle and large clevis pivots out back tie it all together.
The frame features a hydroformed top tube, butted and formed downtube, tapered headtube, and plenty of standover clearance in a 6061-T6 Aluminum package. A threaded bottom bracket promises less creaking than the press fit alternative, and ISCG mounts allow you to mount a chainguide if you see the need. Mud clearance is quite good with the stock 2.35-inch Kenda tire.
While a potential negative for some due to their exposed position under the down tube, the custom cable guides are better than most. Dropper post guides follow the underside of the top tube, and there’s also a Stealth routing option on the side of the seat tube. The bike does lack water bottle cage mounts, the overall package is executed quite well. It seems as though Diamondback has finally nailed most of the small details.
The Mason FS is available in two builds priced at $3,500 and $6,000. We tested the $6,000 Pro build.
On The Trail
We chose to ride the Mason FS on the incredibly diverse terrain in Sedona, which had everything from fast and flowy singletrack to extremely technical rocky climbs and descents. Trails included Slim Shady, Hi-line, Baldwin, Old Post, Ridge, Templeton, and Made in the Shade.
Diamondback did a great job with the cockpit components, which include a 50mm stem and 30.9-inch (785mm) handlebars. It’s clear that whoever spec’d the bike likes to shred, and these parts paired well with the bike’s capabilities. The compact 4.3-inch (110mm, size dependent) headtube works well with the 29er, helping to keep the front end height reasonable. The reach felt on point, and we were right at home immediately. The 24.4-inch (620mm) top tube is average for a size Large, and Diamondback recommends the Large for riders in the 5’10” to 6’1” range which seems on point given our experience. Unfortunately reach and stack measurements are not published.
Given the bike’s rather aggressive geometry, it's obvious that Diamondback intended this bike to be used on as hectic of terrain as the rider can handle. The 66.5-degree head angle is matched with a 5.5-inch (140mm) FOX 34 Float CTD fork with a 51mm offset. This gives you a nice slack feeling but doesn’t compromise the steering characteristics that you would get with a smaller wheeled bike.
The one fault with the bike’s geometry is the length of the chainstays, especially on tighter trails. At 18.3-inches (464mm) they are an inch or more longer than many others in the aggressive all-mountain 29er category. While this provided good stability in high speed sections, we would like to see things balanced out to give the bike the ability to change directions more easily when the trail is slow and tight. The excessive length of the stays could feel worse on smaller sizes.
The bike's strong point has to be its capabilities on the descents. The geometry, suspension design and pure physical mass allow you to point it down and open it up. It may not be the most playful bike due to its weight, but when heading into the roughest sections of trails you can hold your line, pick a new line mid section, or even experiment with sketchy lines that lighter, more nimble bikes want nothing to do with. Most of the mass is around the bottom bracket or behind it, so lifting the front end is still as easy many lighter bikes, despite the long stays.
There was a little flex detectable in the rear end, but it was no where near as much as the Sortie 3 we tested last year. This helped tremendously with the overall handling and responsiveness of the bike.
Small bump sensitivity was spot on, allowing the bike to track extremely well on loose terrain. The back of the bike wanted to push through the chunder rather than bounce or hang up. The shock had great mid-stroke support and was progressive enough towards the end to avoid the feeling of riding too deep into the suspension. G-outs, drops and jumps were dealt with surprisingly well. Downhill square edge hits were absorbed very well, but what stood out even more was the bike’s ability to take the edge off all the square edges on technical climbs. It smoothed out many of the awkward ascents and made it easier to keep the wheel on the ground between rocks and shelves.
FOX’s 34 Float fork paired well with the Mason FS, offering sufficient front end stiffness, decent small bump performance, and a nice progressive ramp at the end that prevented any harsh bottom outs.
At 32-pounds there’s no hiding the bike’s weight, and it definitely has the feel of a heavy rig. Yes, in this day and age you will find much lighter bikes, but we would rather tack on a few extra pounds to the Mason FS and have it work well than sacrifice performance.
In the saddle over rough terrain, the bike is very efficient. Standing up, though, the active suspension design robs some horse power. The bike doesn’t exhibit a large amount of anti-squat so it lacks a snappy pedal response, but then again it tracks very well. Flipping to the “Climb” setting on the Float CTD shock helps improve the ride on smooth portions of the trail.
Climbing efficiency comes from its ability to find traction where other bikes can't. You may have to carry a few extra pounds up the hill, but you will find that you are not spinning the rear tire wasting energy. This was greatly appreciate as we neared the end of a few big rides and tired muscles made things a little sloppy. The Mason can keep a slow and easy cadence while minimizing strain which will help you continue to clean technical climbs hours into your ride. The bike’s length does requires some advanced planning on technical ups, however.
Diamondback did a great job understanding the personality of the Mason FS by equipping it with a pretty smart selection of components. They didn’t compromise performance with anything flimsy, which makes the bike feel solid and doesn’t leave much room for hesitation due to a lack of confidence in the components.
The 2.35-inch Stick-E rubber Kenda Nevegal tires are not the fastest rolling, but they provided sufficient traction on the rock in Sedona when things got steep and rough. For smoother, faster rolling trails we’d suggest something a little less aggressive in the rear. For loose over hard terrain, consider a complete swap for the best traction.
Easton’s Haven wheels performed well. Had Diamondback chosen to put lighter and potentially less stiff wheels on this bike to save weight, that could have had a big impact on the review. The Mason can take the gnar so the wheels better be able to as well.
The Avid X0 Trail brakes combined with a 200mm front and 180mm rear rotor provided plenty of power and modulation. We never found ourselves wishing for more power, even after a few river crossings and sand sections. Two thumbs up.
SRAM’s X01 drivetrain had no issues and the lack of a chainguide gave the whole system a very smooth and drag free feel. Shifting was flawless with no skips or dropped chains. It also quieted the bike nicely and cleared up room to run the Crankbrothers Kronolog dropper post lever where a front shifter would normally sit.
While we’ve had a few poor experiences with the mechanical Crankbrothers Kronolog seatpost in the past, this post worked flawlessly.
Long Term Durability
The components and frame are definitely worthy of being abused for the long haul. The frame is quite stout compared to previous Diamondback 29er designs, and the pivots remained tight during our test.
Diamondback's warranty policy provides up to five years of coverage for the frame, and all suspension components (including the swingarm and linkages) are covered for one year.
What's The Bottom Line?
From the moment we threw a leg over the Diamondback Mason FS Pro 29 we were pleasantly surprised. It feels comfortable immediately, inspires confidence when the trail gets rough, and the aggressive geometry is suited to letting it rip on the descents. Dropping in for the first time it was clear we were going to have fun on this bike. While it’s not the most agile due to the rear end length, the stability, suspension performance, and rear end stiffness improvements allow you to focus on getting nasty.
Yes, it weighs a decent amount, but there is a lot to be said for a bike that does the job without a single hiccup. The added heft also helps the bike carry speed where others slow down, and makes us inclined to think that it’d be a good match for riders that really put their equipment to the test. Remove any preconceptions from your mind, the Mason FS is the real deal and ready to take what you can dish out.
The only major point of contention is the price tag, because at $6,000 you can pick up some very nice rides, many of which are of the carbon variety.
Visit www.diamondback.com for more details.
About The Reviewers
John Hauer - In 13 years of riding, John has done it all and done it well. Downhill, 4X, Enduro, XC, cyclocross... you name it. He spent 7 years as the head test rider for a major suspension company, averages 15-20 hours of saddle time per week, and is extremely picky when it comes to a bike's performance. And yeah, he freakin’ loves Strava.
Jess Pedersen - Jess is one of those guys that can hop on a bike after a snowy winter and instantly kill it. He's deceptively quick, smooth, and always has good style. He's also known to tinker with bikes 'til they're perfect, creating custom additions and fixes along the way. Maybe it's that engineering background...