When the 429 SL first debuted as Pivot’s ultimate World Cup-caliber race weapon it was long, low and slack, at least for its time. Signaling a change to the new era Pivot’s cross-country bike is now named the Mach 4 SL providing 100mm of a renowned dw-link suspension paired with either a 100-120mm travel fork.
Even though the bike is intended to be a cross-country bike, I cringe a little to call it that. With reach numbers equivalent to Pivot’s short-travel shredder, the 429 Trail, the new Mach 4 SL is more than just a “cross-country race” bike; it’s a bonafide mountain bike that absolutely rips.
The most apparent change to the Mach 4 SL is a vertical shock layout. The shock placement offers the same anti-squat numbers if it were mounted in-line with the top-tube but allows a more compact frame design. By rotating the shock, Pivot was able to improve standover height and bottle clearance in the smaller frame sizes as well as create better integration with Fox Live.
Pivot was able to shave an additional 300 grams off the Mach 4 SL compared to its already feathery predecessor, the Mach 429 SL for a frame weight (without shock and hardware) of 1,845 grams. Updates include an integrated headset, carbon-bearing pockets for the rear suspension linkage, a compact rear triangle with skinnier tubes and a stiffer lower chainstay since there is no front derailleur to worry about and further optimizing the shape of the tubes.
GEOMETRY & SIZING
The geometry updates for the Mach 4 SL are not only comparable to other modern bikes in its class but offers some attractive advantages. For our size large, the seat tube length lost 2-inches compared to its predecessor allowing more dropper post compatibility. With a 120mm fork, the head tube angle sits at a slack 67.5 degrees which is a degree slacker than the Santa Cruz Blur and 3-tenths of a degree more slack than the Yeti SB100. Standover has been substantially improved on as well, sitting 2-inches lower than the Mach 429 SL and an inch lower than both the Blur and SB100.
Pivot offers the Mach 4 SL in a 29-inch wheel only but a full-size run of extra-small through extra-large to cover riders 4’10” – 6’7″. In addition, the extra-small will fit a large bottle inside the triangle and provides a lower standover height than the Mach 4 Carbon with 27.5″ wheels. The extra-large Mach 4 SL offers two bottles mounted on the downtube inside the triangle.
The new Mach 4 SL is available in three color options – Team Blue, Cherry, and Stealth. It is available as a frame, frame kit, and a complete bike in multiple configurations, ranging from $4,599 to $11,299 USD. For more information, visit Pivot Cycles website.
There is no denying the fact that I am a fanboy of down-country bikes. In the grand scheme of mountain bikes, an over-forked cross-country bike with some meaty tires is what I recommend to most riders. It’s more than capable of handling drops and chunk as well as being lightweight enough to make epic all-day adventures possible.
The first two days consisted of 18 Road and Kokopelli loops in Fruita, Colorado. Both offer a mix of high desert terrain of fast and flowy, steep ups with a sprinkling of whoops, jumps and chunk. While the focus was getting out to enjoy the ride of the new whip and dial in bike set-up, the third day was race day. After all, “the Mach 4 SL is a total cross-country rocket ship,” says Pivot Cycles president and CEO Chris Cocalis. So, what better way to find out then to embark on the Epic Rides Grand Junction Off-Road race. The 40-mile loop is a true mountain bikers course offering a steady 1,800′ (chunky) gravel climb and super technical singletrack through the Tabegauche Trails (aka Lunch Loops). All in all, an incredible course for someone who loves fast technical riding, doesn’t mind earning their descents the (extra) hard way, can handle a bit of exposure and maneuvering between, in and around jagged rocks.
I am 5’10 with a 32.5″ inseam and found that I typically ride a size large and a shorter stem. The Mach 4 SL was no different, I was set up with the size large frame size and switched from the stock 75mm stem and 740mm handlebar to a 60mm stem and 760mm handlebar. The only other tweak I would have liked to make was swapping to a more voluminous tire like the 2.35 Ardent Race or maybe an Ardent Race 2.35 / Rekon 2.6 combo.
The Mach 4 SL I was riding for the weekend also featured the Fox Live suspension system. The system has sensors in the fork and rear axle collecting data 1,000 times per second with the ability to adjust the suspension within 3-milliseconds. That’s one hundred times faster than a blink of an eye. There are five modes, the fifth setting requiring the most amount of input for the suspension to open for a firmer feel and the first setting which requires the least amount of input from the sensors and rider. Chris had suggested starting on the third mode, but I found myself liking the feel of the second mode during the race and preferred the first mode while riding at Kokopelli.
From a racers cross-country race rig perspective, it’s all about efficiency and not wasting any energy and the Fox live system works exceptionally well if you are willing to give up roughly a half-pound. The system is half the weight of a dropper post, but still, when you are fighting for marginal gains, grams add up.
For the average rider, weight is less of a concern, the fewer levers, and do-dads on the handlebar, the better. However, I felt it rode a little on the firm side for my liking. Typically, I prefer more plush off the top, keeping the fork wide open and tend to lock-out the rear shock only as needed. I want to spend more time on the system as I see a lot of benefits and could be if used regularly would make me a more efficient rider. One characteristic that was mentioned by another rider was that the bikes suspension remained even through a bermed corner whereas with a standard suspension system the front end is loaded with more of the rider’s weight thus creating a more balanced and in-control feel.
Overall, Fox Live is seamless and super clean since it doesn’t require any additional levers on the handlebar. I also found the timing of when the system opened and closed to be instantaneous; there was no odd delay or hiccups while riding. It truly allows the rider to focus on pinning it regardless if an unexpected steep pitch veers its ugly head or you turn a corner after a climb and are presented with a fast descent with a series of water bars.
During the first pedal strokes and the official parking lot tests (i.e., bunny hops, wheelies, and a slalom course made from imaginary cones), the best way to describe the Mach 4 SL is spunky. It’s light and agile as a short travel 29er should be, but it doesn’t have that twitchy feeling that many World Cup cross-country bikes have. My weight felt centered and inside the bike rather than front end heavy creating a more relaxed body position.
Even with the Fox Live system off and the suspension fully open, the bike maintains an efficient pedal, as one would expect from Pivot. Also, the steep ups I was able to quickly stand-up out of the saddle mashing my way to the top with little wasted energy from pedal bob.
The Shimano XTR 12-speed felt buttery smooth, after riding a handful of bikes with SRAM it was nice to get back on Shimano again. Even with my low-lander legs, I thankfully never had to go into the 51 tooth cog, but it was nice knowing I had it there as a back-up as I made my ascent up the grueling Windmill Road climb.
Descending on the Mach 4 SL felt smooth, controlled and effortless. The bike maintains it’s composure through even some of the more dicey terrain that many would question if a “cross-country” bike could handle. Perhaps maybe that’s it’s a weakness, it feels too much like a trail bike on descents, and you can gain too much confidence. I ended up eating some high-desert dirt over in 18 Road after I decided to get a little sendy while the cross-winds were having their own party.
From the initial pedal strokes stuntin’ around in the parking lot, to the final miles of the 40-miler Grand Junction Off-Road race, the Pivot Mach 4 SL is a pure ripper. It climbs as a cross-country bike should and descends like a short-travel trail bike.
Riding photos courtesy of Cody Wethington/ Pivot Cycles