Pivot’s new Mach 4 SL is the latest of Pivot’s quiver to gain a straighter-looking frame and updated geometry, dropping significant weight in the process. Built around the well-loved DW-link suspension platform, the leaner, meaner Mach 4 SL replaces both the Mach 4 and the Mach 429 SL as Pivot’s sole full-sus XC option.
In keeping with the ongoing 29er domination of the XC scene, the Mach 4 SL is available only with 29-inch wheels, all the way down to its XS frame size. Pivot proto-typed both a 27.5-inch bike and a 29er, but found that pro team racers generally preferred the rolling momentum gained with the larger wheel size. Plus, with most 27.5-inch tire development going toward bigger, more aggressive endeavors, 29-inch wheels give racers the greatest XC-width tire selection.
Smaller riders will appreciate the influence of petite Pivot athlete and Olympian Chloe Woodruff, who worked closely with the brand to ensure that the bigger wheel size wouldn’t compromise standover or maneuverability. The result is a bike that actually has a lower standover and a shorter seat tube than the 27.5-inch Mach 4—and happily fits a full-sized water bottle in all frame sizes. The Mach 4 SL is available in XS-XL, which Pivot claims are suitable for riders from 4-foot-10 to 6-foot-7.
Pivot lightened the frame by 300 grams (compared to the previous Mach 4) through refinements in its molding process and by using carbon bearing “pockets,” rather than standard aluminum cups; other than the headset, this frame has no metal in it. The rear triangle was also trimmed down, with a higher chainstay, shorter seatstays, and svelte dual uprights rather than the beefier (i.e. heavier) load-bearing single tube used before.
The Mach 4 SL uses a press-fit bottom bracket, which might dismay some, but as one of the pioneers of the very concept of press-fit bottom brackets, Pivot defends its decision; bonding a threaded bottom bracket shell to the frame creates weak points and interface issues—which Pivot claims ultimately cause the majority of frame warranties. Pivot also holds its bottom brackets to the same stringent tolerance standards as its headsets, for an ostensibly snug, creak-free fit.
Riding the Mach 4 SL:
Simply put, the Mach 4 SL brought out some of my more destructive XC urges (stomp pedals, throw elbows, win press camp) and I’m not sorry about it. Of course, it’s no surprise that a lighter, stiffer Mach 4 with the latest components, modern geometry and fast-rolling 29er wheels turned out to be a sweet race bike. But where I think this bike really shines is its versatility—and that word isn’t code for ‘not really a race bike.’ Rather, I think that this is an amazingly light, strong and versatile frame that can be made into exactly what the rider needs it to be.
Let’s start with the wheels. For the Mach 4, 29-inch wheels were the obvious choice. This is a cross-country bike after all. It has little use for popping and flicking. In exchange for that pop, the Mach 4 SL offers a little more margin for error on technical descents and a little more float on technical climbs.
The moderately steep headtube (67.5 with the 120-millimeter fork I rode) and shorter rear triangle probably contribute to this—you feel like you’re in a nice balanced place between the wheels for good control and power transfer. Like most bikes these days, Pivot went with 148 Boost spacing to give the bike a wider, stiffer BB without ballooning the q-factor of the bike. You can feel it when need to pop a wheelie over a ledge, or hammer out a few miles of fire road. Combined with the superb anti-squat characteristics of the DW-link platform, even fully open this bike feels super efficient.
It would be easy to draw a comparison between The Mach 4 SL and modern versatile XC rigs like the Yeti SB100, but having ridden both I think I’d choose the Mach 4—it feels more substantial without being cumbersome, and somehow more composed the dicier things get.
The bike I rode came with a Fox Factory 34 SC 120-millimeter fork. But you can also choose a 100-millimeter fork (both have 100 millimeters of rear travel). The 120 slackens the headtube by a degree and makes the bike both heavier and taller—but that’s easy to address with stem/stack/bar setup if you like a lower position. All said, you can choose from 22 different full builds, from the Race XT build with a 120-mil Fox SC 34 and Performance DPS shock ($5,000) to the Team XX1 AXS build with Fox LIVE VALVE, which will run you more than $11k.
Ultimately, this bike gives you all the XC options you could ever want. Need an emaciated race weapon? It can be that. Need a light, capable whip for your local XC trails? It’s more than happy to be that too. As I see it, the main question for this bike is whether to spring for the available LIVE VALVE suspension upgrade.
Riding LIVE VALVE
The Mach 4 SL I tested was “live,” or outfitted with Fox’s freaky-deaky new LIVE VALVE technology. The electronic suspension control system senses variations in the trail and opens or closes the fork and shock accordingly—a premise that I was admittedly very skeptical of, especially for an added half-pound and $1,900.
I like simplicity and consistency, especially in a race setting. In my experience, anything that can go haywire in a race will go spectacularly haywire, so trusting something as important as suspension performance to a literal bundle of wires felt gimmicky at best, and straight-up crazy at worst. Given the wild variations of our test trails around Grand Junction (and the 40-mile Grand Junction Off Road marathon looming at the end of the week), I was worried I’d made a terrible mistake committing to ride a bike I’d never seen.
Now, after spending roughly 70 miles and eight hours in the saddle getting to know LIVE VALVE, I’m just worried other bikes will seem, well, dead.
Colorado’s Western Slope trails are notorious for dishing up flow-packed clay ribbons, square sandstone edges, rock-shard gullies and serious exposure—all in the blink of an eye (about ⅓ of a second). Fortunately, LIVE VALVE responds even faster than that. Think 1,000 times a second. If the system senses input, it responds in 3 milliseconds. We humans, on the other hand, take a leisurely 12 milliseconds to even notice.
LIVE VALVE engages an average of 480 times an hour during normal riding, and more than 700 times during an average XC race. In other words, that’s 700 times you don’t have to think about locking or unlocking your shock, so you can focus on tearing peoples’ legs off instead.
The internal accelerometer also measures three axes of movement (fore-aft, up-down, and side-to-side) and makes specific adjustments for each. If it senses you’re climbing a grade of over 5 percent, for example, it will open up the front when triggered, but keep the rear a little stiffer for pedaling efficiency. If it senses you’re in the air, on the other hand, it will open everything up for a soft landing.
What does that translate to on the trail? A bike that felt like the perfect bike for the job, all the time. It was a twitchy, aggressive hardtail that melted into a plush trail bike the instant I felt like plowing through a rock garden. Support through high-velocity corners was flawless, and it gave me just the right balance of traction and efficiency through jumbley climbs. It took all of five minutes to trust the system completely, and I never looked back.
The nitty gritty: LIVE VALVE consists of a toptube-mounted control box, which also contains the battery. This is internally wired to controllers in the fork and shock. The system has five levels of responsiveness, similar in concept to damping control—you can decide how much input (i.e. how big a hit) is required for it to respond. Sag and rebound are set normally.
Fox says the battery will last you between 20-40 hours ride time, depending on how often the system engages. Fifteen minutes charge (via micro-USB) gets you an hour’s ride time; two hours gives you a full charge. If you opt for LIVE VALVE when you order a Mach 4 SL, it runs you around $1,900 for the upgrade. Aftermarket, it’s between $3,200 and $3,300, depending on the suspension you choose—LIVE VALVE forks and shocks are tuned differently than standard ones, so your whole suspension setup needs to be replaced if you decide to upgrade after the fact.
Is it really better than a well-tuned shock with the right linkage for your ride style? This is a question I struggled a bit with over the week, because I want to say that a perfectly dialed setup is all anyone needs. Ultimately, I think that is still true for most types of riding—but the luxury of LIVE VALVE was hard to deny. Not only does it reduce mental and physical fatigue over long miles, but it gives the bike a distinctive personality—it feels like you’re in constant conversation with the bike, instead of just riding it.
I can relate to the skeptics who feel a visceral sense of wrongness about the idea of having to plug in a bike. There is something real about preserving the simplicity of our experience on the trail, and the encroachment of e-bikes and electronic shifting can make this feel even more important.
But this is also just a really impressive piece of technology that makes for a (vastly, remarkably, cynic-convertingly) more seamless riding experience. It might seem unnecessarily wired and expensive right now, but I wouldn’t be surprised if fork and shock lockouts eventually go the way of the front derailleur and robots get a lot more streamlined and affordable. It’s only by trying these crazy things that we get to keep seeing mountain bikes get cooler—and the Mach 4 SL with LIVE VALVE is definitely one of the cooler bikes I’ve ridden to date.