Pivot's inaugural model was the Mach 4, a cross-country oriented 100-millimeter-travel dual suspension bike. Its aluminum chassis incorporated a number of innovations, like rockers and bottom bracket assemblies that were welded together from two halves to form lightweight hollow structures, and Pivot also was one of the first bike brands to commit to Dave Weagle's anti-squat suspension technology. Much has changed since then, most notably the public's perception of the basic cross-country trail bike. Unless one happens to be an XC racer, most trail riders are choosing suspension travel in the neighborhood of 120 to 140 millimeters, largely because there is little if any weight penalty for moving up to a more capable chassis, and also because suspension no longer is a pedaling efficiency issue. Pivot, however, believes that many hard-core riders and racers out there long for the snappy acceleration and razor-sharp handling that the Mach 4 was born to deliver, and that the role of the short-travel dual-suspension bike is more valid than ever, so much so that they threw every trick they knew into this week's featured test bike: the Mach 4 Carbon. Meet the Mach 4 CarbonImproved numbers:
• Carbon frame and swingarm, four-bar dw-link suspension, PressFit 92 bottom bracket, 115mm rear travel, 27.5" wheels
• Internal cable routing, Shimano Di2 compatible, with Pivot cable-port system
• Dropper post compatible with internal or external routing
• Shock: Fox Float CTD Kashima
• Fork: Fox Factory Series Float 32 CTD, 120mm, Kashima
• Enduro Max cartridge bearings at suspension pivot locations
• Stainless steel chain protection plates and rubberized leather frame protection pads.
• Bottle mounts above and below the down tube
• Direct-mount front derailleur bosses
• Clearance for tires up to 2.35"
• Sizes: X-small, small, medium (tested) large, and X-large
• Colors: grey/green, carbon/blue, carbon/red, carbon/pink
• Weight: 5.1 pounds (medium frame) with complete builds beginning at 22.pounds (10kg)
• Weight as tested: 27.1 pounds (12.32kg)
• MSRP: frame only - $2899, estimated price as tested, $10.000 (Pivot offers complete bikes, outfitted with either SRAM or Shimano components, ranging from $4499, to $10,249 USD.
• Contact: Pivot Cycles
Pivot founder and designer Chris Cocalis upgraded the Mach 4 from 26 to 27.5-inch wheels when he decided to release a carbon fiber version, which required all new geometry and gave him an opportunity to upgrade its numbers to reflect current trends. Rear suspension travel has been increased from 100 millimeters to 115, which seems like an unusual number, but those who know Cocalis will tell you that the man wouldn't have chosen 115 without an extensive evaluation of travel numbers between 100 and 120. The dw-link suspension was reconfigured to drive the shock with a lower leverage rate, which increases the effectiveness of damping and tuning adjustments, as well as extends the range of rider weights that an air-sprung shock can handle. Up front, the Mach 4 is configured for either 100 or 120-millimeter-stroke forks (a 120 is preferred).
The carbon Mach 4's geometry is slightly slacker, with a 68.2-degree head angle and a 72-degree seat angle. Pivot offers the newest Mach 4 in a five sizes, from X-small (which has been especially designed with 100 millimeters of travel, a lower stack and an impossibly low, 26.61 inch standover height), to X-large. Complete Pivot Mach 4s range from the $10,249 Shimano Di2 build, to a far more affordable, $4,499 Shimano SLX-based build. The frame-only option runs $2,899 USD.Carbon construction:
The Mach 4 is a complicated frame design and Pivot is justifiably proud of the carbon construction methods used to manufacture it. While some of the techniques used are trade secrets, what we do know is that the carbon layups are wrapped around rigid forms which are molded into the final shapes of the frame and swingarm. This sizes the many layers of the flexible carbon layup to closely match the inside of the molds which produce the frame parts. That in turn assures that the carbon is compressed evenly as it is cured using heat and internal pressure. When the parts are removed from their curing molds, they look ready to ride. Their precise layup and molding protocol allows Pivot to use less carbon, and as such, they can put higher strength (read, more expensive) material in key places without wasting the material's properties, because the maker can assure optimum compaction and fiber orientation in those critical areas during the manufacturing process. Just because the frame is built with "high modulus carbon" doesn't guarantee that it is any stronger. The entire process must be optimized to take advantage of it. Pivot seems to have done it right, because the Mach 4 is as beautiful to look at as it is to ride. In case you wondered, the weight of a medium Mach 4 frame is said to be 5.1 pounds (2.3kg).
Oft overlooked, the Fox D.O.S.S. dropper post was well suited to the Mach 4's performance. The positive feeling mechanical action offers three positions: up, down and trail. We found the middle position to be perfect for techy, fast-paced trails where we wanted a bit more control.Component Notes
Versatile features: Because many customers order Pivots as frames only, and also because Pivot offers the Mach 4 Carbon in a variety of Shimano and SRAM build options, there is a direct-mount provision for a front derailleur, and cable and hose routings are strategically placed to ensure that any popular component will be compatible, from droppers to disc brakes. Most of the cable and hose routing is internal. We picked up our Mach 4 in conjunction with Shimano's release of its electric shifting Di2 XTR drivetrain because it was the first production MTB chassis to be designed to work directly with Di2. The battery is screwed into a special port below the downtube and there are sealed wire ports where necessary in the frame. At the head tube, special screw-down hatches allow the right-side cable access ports to be converted from standard hose and housings to Di2's e-tube wiring. Pivot's internal routing assures that all the bits inside are secured and protected, and that the chassis looks cleaner and less complicated
Suspension: The latest Mach 4's suspension has been reconfigured with a reduced leverage rate that pencils out to 2.59:1. The idea is to reduce pressure levels required to maintain proper sag, and to boost the sensitivity of the shock's damping in both directions. Cocalis says the short rockers and one-piece swingarm design provides much more stiffness than a single-pivot or Horst-Link suspension. Long-wearing Enduro Max ball bearings are used at all pivot locations, and the lower rocker is offset to the left to add width to the rocker and to maximize the lateral stiffness of the chassis. Like all Pivots, the Mach 4 is configured with dw-link anti-squat kinematics, which means that you'll probably never have to use the shock's CTD lever to boost its pedaling effectiveness. Dw-link designs, however, seem to be sensitive to compression damping, so the Fox Float CTD damper and air-can are custom tuned, and while that is what we would expect from all good bike designs, it is essential to the Mach 4.
Normal reviews call for testing models outfitted with standard, production-line components, but our Mach 4, was sent to Shimano to be outfitted with its house-brand Pro cockpit items, XTR carbon wheels and a Di2 XTR component ensemble. Pivot offers their own version based upon Shimano Di2 XTR, but it features different cockpit items and a Reynolds carbon wheelset which result in a slightly lighter overall weight figure and nearly the same MSRP. Our test bike also featured a Fox D.O.S.S. dropper post, which is not available from Pivot. The test was conducted using a 2.25-inch Maxxis High Roller II front tire, with a 2.2-inch Maxxis Ardent rear tire - both converted to tubeless. (The High Roller II and the Ardent are standard options for the Mach 4.)
Because we are going to post a long-term review of the Di2 ensemble shortly, we will avoid covering the performance of individual components beyond their relevance to this particular review. For the drivetrain, we used the two-by eleven Di2 option, programed in the synchronous mode. The right-side shifter buttons control both the front and rear derailleurs, providing 13 evenly spaced, pre-determined gear selections. The Mach 4 frame is literally built around Di2, and the installation was so seamless that most observers were unaware of its presence until they heard the servo motors at work.
|The Mach 4's cross-country roots are not lost in its modernized suspension and geometry - it feels speedy and efficient, and it requires its rider to be engaged. |
Reviewing a top-food-chain version of the classic short-travel cross-country trail bike asks more questions than it answers. On one hand, Pivot's Mach 4 Carbon represents near perfection of that genre. Its chassis has evolved from a single-purpose racing machine to become a race-oriented, but far more capable tool for backcountry fitness junkies who talk heart rate, log ride distances, and preach Strava. On the other hand, the Mach 4 Carbon has reached a point in its development where it can neither turn back to its racing roots, nor progress forward to join the super-slack enduro-bro genre which has recently captured the imaginations of riders who deem themselves to possess greater technical skills than the average Joe or Jane and thus require uber capable mounts. Its lightweight carbon chassis is remarkably stiff under power and, combined with its anti-squat suspension, the Mach 4 Carbon can be powered up in an instant from a seated or a standing position. Get it rolling fast, and its compact wheelbase and minimal suspension communicate a clear picture of what's going on beneath the wheels. Its cross-country roots are not lost in its modernized suspension and geometry - it feels speedy and efficient, and it requires its rider to be engaged. Initial setup:
Long-travel trail bikes require far more attention to get their suspension right because the more travel you have, the more it affects the outcome of your ride. By contrast, the Mach 4's paltry 115 millimeters needs only to be sagged in correctly (a built-in sag-o-meter assures that you can't get that wrong), and that you have cranked in the low-speed rebound sufficiently to prevent the tail end from bouncing after singletrack-pace G-outs. Fox's 32 Float CTD fork is equally easy to dial in, although, using the 20-percent sag rule allowed the front end to devour its travel when descending steeps, so we changed that to the 15-percent rule.
Like all short-travel (or no-travel) cross-country oriented trail bikes, fine tuning the suspension is done primarily with tire selection and pressure settings. The Mach 4 performed remarkably different when we experimented with various tires. It prefers a fast-rolling, high-volume tread like the Schwalbe Rocket Ron or the Maxxis Ardent, but unless you are planning a 100 kilometer trail ride or entering a marathon XC event, you will happily give up their faster roll and dexterous feel for a grippier tread that is more predictable in the turns. Ultimately, we settled upon a compromise, with a 2.2-inch Maxxis Ardent in the rear and the industry standard, 2.25-inch Maxxis High Roller II up front. Paradoxically, the exact tire combination that Pivot specs on its complete builds. Running tubeless, the best tire pressures were 28psi up front and 30psi (apx. 2 bar) in the rear with rider weights between 160 and 170 pounds (apx. 70 kg).
Climbing and acceleration:
|The rider's position over the Mach 4 Carbon makes for a seamless transition to and from the saddle.|
Inexplicably, Pivot's blend of new and old-school geometry produces a bike that lacks some of the explosive pop that the original Mach 4 had out of the starting gate and up short, steep climbs. The Mach 4 Carbon can get moving in a hurry, but where it shines best, is its ability to carry speed on the flats and to maintain a strong pace uphill. Some of that tendency could be attributed to the fact that the rider's position over the Mach 4 Carbon makes for a seamless transition to and from the saddle. We'd chalk up the rest to anti-squat and its lightweight, rigid chassis.
Technical climbing was hindered slightly by the Mach 4's lower-than-necessary bottom bracket location, which botched some possible first ascents when I slammed a pedal or a chainring at the most inopportune moments. Pivot pegs the Mach 4's bottom bracket height at 12.8 inches with a 100mm fork and 13.25 inches with a 120mm slider. Our test bike, with a 120mm Fox 32 fork, measured 13 inches, shod with huge, 2.35-inch tires. That said, if you can avoid banging the cranks and pedals, the Mach 4 Carbon can claw its way up some serious gnar. I used the Pivot to explore some lung-bursting technical ascents that featured relentless boulder and switchback problems, and can report that the bike helped me pull off some improbable moves. Its rear suspension seems to dig into the terrain with each power pulse. Technical climbers should know that Di2 absolutely rocks. I never had to worry about a shift. I learned I could push the button, trust the computer, and concentrate entirely on bike-handling skills.Cornering and Steering:
While the Mach 4 is quite capable of the "look at me drift" that has become the defining slack-head-angle move, its steeper geometry and shorter wheelbase gives it more bite in the turns and it tends to carve a tighter arc with a slight tendency for the rear wheel to slide before the front tire breaks traction. When the Mach 4 does break into a drift, it keeps searching for traction, which maintains momentum and improves exit speeds. Those familiar with the Maxxis Ardent 2.2-inch tire, however, will agree that it grips until it doesn't grip, after which, it lets loose with a suddenness that put me on the ground at least once. Those who favor predictable cornering over lower rolling resistance should probably choose a gripper tread like the High Roller II for its tail end.
Steering is light feeling and predictable, but after riding head angles in the vicinity of 66 to 67-degrees for a season, it took some time to adjust to the Mach 4's quicker feeling, 68-degree number. The steeper angle makes the Pivot extremely agile mid-corner, and it presents many more options when it is necessary to scribe a precise line down a rock garden. But, all that goodness comes at a price when you get up a head of speed and the best approach is to straight-line the boulders, and line choices are limited to one. If it strays off line in the heat of battle, it will be up to you to coax it back to safety. In the hands of a competent rider, the Mach 4 can rip, and it can handle a lot of punishment - but you'll have to look and plan ahead.
|Its steeper geometry and shorter wheelbase gives it more bite in the turns and it tends to carve a tighter arc... |
Shimano XTR brakes, paired with a 160/180-millimeter rotor combination provided more than enough stopping power for precise control on the downs, and their feel was better than I remember, with just-right modulation. The Mach 4 can handle steep and technical descending as long as its pilot doesn't go in too hot. There seems to be a fine demarcation between the Mach 4's thrilling-but-in-control speed and its Hail Mary threshold. You will not forget the lesson, I can assure you. Within its envelope, which reaches well into, but does not fully encompass the domain of all-mountain, Pivot's Mach 4 Carbon is a trustworthy and very enjoyable partner, so much so, that I often would choose it for rides that would put it well out of its comfort zone, because I knew that it would be more rewarding for the lion's share of the chosen route.
Like most XC-oriented designs, the Mach 4's rear wheel tends to lift when jumping unless you exaggerate the pull-up slightly. Otherwise, it flies pretty well. Its limited suspension travel makes it skip around a bit under braking at speed, and it will do the same while rounding fast, rough corners. Happily, the chassis is laterally rigid to the point where none of that bouncing seems to throw it off line. I found the medium size to be just right for me, which means that riders nearer to six feet tall should probably choose a large size. I found that I was up against the handlebar when I was climbing up steep rock faces or launching up steps on the trail, and I am fairly short (five-foot, seven inches/170cm). In its favor, the Mach 4 requires very little fore/aft movement to weight the wheels when maneuvering the bike, and it can be had in five sizes, so most riders are assured a good fit and a proper handling bike. Issues:
Looking back at the Mach 4 Carbon review, I would probably choose a longer stroke fork if I were to make the bike my daily rider. A 130mm or 140mm fork would raise the bottom bracket slightly and kick the head angle out to about 67 degrees, both of which would extend its comfort zone in the technical type trails which I ride most often. Of course, that pushes a bike which is clearly intended to be a lightweight XC trail machine into the realm of all-mountain. While the 32-millimeter Fox fork is considered to be taboo by hard core riders, it puts in a sufficient performance in the shorter, 120-millimeter length. I learned to use the "Trail" option to add support when I was descending in earnest, which worked out well. I blew up the shock in about two months, however, which may have been another reminder of the bike's intended purpose. Failures of Float CTD shocks are few and far between in the true realm of XC/trail riding, but mine leaked some fluid and sucked some air. Evidently, the Mach 4's 115 millimeters of travel are not negotiable. Other than that, the only problems I had were snapping a carbon XTR brake lever and losing the retaining screw for Pivot's through-axle nut at the rear dropout. The derailleur hanger is integrated into that part, so when I pulled the rear wheel out, the rear derailleur fell off - more of an annoyance than a serious problem. Technical Notes:
Overall the Mach 4 Carbon was a trouble free, quiet running trail bike that took a beating and was always waiting for another go. As mentioned earlier, the Pivot's build kit was intended to showcase Shimano XTR M900 and Di2 XTR M9050 components which will be covered in a future review. That said, we did have some positive and negative experiences with the bike's components worth mention.Carbon brake levers:
Shimano XTR carbon brake levers are not immune to failure. We snapped one on the last day of the review period. Who would have guessed that, after crashing and bashing for three months, the tip of the lever blade would pop off when the bike fell over by itself in soft dirt? I sanded it smooth with a rock and called it good
Fox D.O.S.S. dropper post: It's heavier than the Reverb, it only has three positions, and it has an external housing. And you know, I couldn't care less. The Fox dropper was the perfect mate to the Mach 4's performance - the middle position was the ticket for long, fast-paced descents or anywhere I anticipated trouble and, unlike the infinitely adjustable Reverb, I could flick the Fox's black lever and find the same location - every time. Turns out, I like it.
Di2 Synchronous shifting: Awesome. If you are going to have a front derailleur, then you should have one that shifts by itself. The difference between electric shifting and manual is that you must hold onto the manual lever until the shift is complete. With Di2, you press and forget. Small deal? Try it before you pass judgement. Di2 only offers one gear higher and one lower than SRAM XX1. I found that I liked the extra low and rarely used the taller option - still, having two extra gears in the bank turned out to be a good thing.
|The frame alone of Pivot's Mach 4 Carbon costs as much as a good quality, entry-level, dual-suspension trail bike and it would take over three times that sum to duplicate our test bike. The message here is that you should be absolutely sure of what you want before laying down that kind of cash for a mountain bike. The good news is that Pivot makes that task easy. The Mach 4 Carbon is beautifully designed and executed to fulfill a specific role: a no-compromise cross-country trail bike, built tough enough to last a lifetime, and light enough to ensure that its owner need not wish for something else a few years down the road. If you own an elite level XC bike, have a few bib shorts hiding in the closet, collect KOMs on Strava, and have a burning desire to get rowdier than the rest of the boys and girls on your weekend cross-country rides, the Mach 4 Carbon will show you a whole new world. - RC|
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, @foxracingshox, @Maxxis