Mountain Bike Action Bike Test: Pivot Mach 4 Carbon SL
Pivot Mach 4 Carbon SL
By 2016 I had a few Leadville finishes to my name, and that is also the year I went sub-9 hours for the big belt buckle (goal accomplished). For some reason, I keep coming back, and each year I learn more. Last year I made a last-minute decision to race across the sky after another DNF at the Dirty Kanza 200. Let’s just say I felt like I needed to punish myself a bit at high elevation.
As I looked at my aging fleet of bikes, I reached out to MBA to see if they had anything in the stable that could fill the void. This is where the new Pivot Mach 4 SL came in. The new offering replaces the Mach 429 in Pivot’s line and takes the reins as the new XC and trail race rig—perfect for a long day in the saddle above 10,000 feet, as well as trail riding at home.
The Mach 4 SL is a short-travel, 100mm, full-suspension carbon bike that rolls on 29ers. Both the front and rear triangles are made using Pivot’s carbon Hollow Core internal molding technology, and Pivot claims a frame weight of 1845 grams. That’s 300 grams less than its predecessor (the Mach 429 SL), but Pivot also claims it’s stiffer. Also new is Fox’s Live Valve integration and, in our case, installation. The geometry was designed to be paired with a 100–120mm fork to meet the growing demands of XC courses.
All cables and hoses are run full length internally. There is also routing for an internally routed dropper post. The most noticeable change is the vertical positioning of the rear shock in the triangle rather than horizontal along the top tube like its predecessor. The frame has Boost spacing, along with a full-carbon Press-Fit 92 bottom bracket shell.
When it comes to build options, the Mach 4 SL is downright crazy. There are currently 22 complete builds available, as well as five frame options. And none of those have anything to do with color as an option. Pivot sent us its near-top-of-the-line build called the Team XTR with a 120mm Fork & Fox Live Valve. It will set you back a whopping $10,400 and features Shimano’s 12-speed mechanical XTR drivetrain matched with a carbon 34t Race Face Next SL crankset. The 10-51t cassette offers plenty of range for everything from steep climbs all the way to race-pace downhills.
The cockpit is supplied with in-house Phoenix Team flat carbon bars at 760mm matched to an alloy Phoenix Team XC/trail stem and PadLoc grips. Our size medium build came with a Fox Transfer 125mm dropper post, same as the one on small and large frames, but a KS Rage-i 100mm comes on the XS and a Fox Transfer 150mm comes on the XL. This is topped with a WTB Team Volt saddle with titanium rails.
Keeping things moving is a lightweight set of DT Swiss XRC 1200 Spline 25 wheels. Unlike the normal DT Swiss offering with 180 hubs, ours have DT Swiss 240 hubs and use the 36t star ratchet in the freehub. The 29er carbon rims have an internal width of 25mm with an external width of 31mm. A set of Maxxis Ardent Race 29 × 2.2 TR, EXO tires is sealed using Stan’s sealant. Last but not least, a set of 160mm center-lock XTR rotors is matched with dual-piston XTR brakes.
Fox Live Valve is the big news for our test bike, and it also adds almost $2000 to the build compared to the equivalent bike without it. In the rear, we have the Fox Factory Live Valve shock set at 25-percent sag (10mm) rather than the 30 percent (12mm) that the sag indicator represents. It’s on a dw-link and is modified for XC racing. In front is the120 mm 29er Fox Factory Stepcast Live 34 with 44mm offset that we also set to 25-percent sag (30mm).
Both the fork and shock have low-speed compression damping that can be tuned for the open mode. We had both set one click from the softest. We also ran the rebound on the fast side. The real workhorse in the system is the controller that adapts to the terrain at 1000 times per second. Adjustments happen in 3 milliseconds for an almost unregisterable transition from closed to open and back.
There are three sensors: one on the fork, one on the furthest point of the chainstay and the last one in the cradle of the controller. Using these three sensors, the controller knows the position of the bike relative to level as well as the force of an impact at either wheel. The system then reacts accordingly, depending on if you are climbing or descending. The controller also has a free-fall sensor, so the suspension will open while you’re in the air instead of relying on a fork or chainstay sensor for impact.
The controller has two buttons with five threshold settings. The power button does as you would expect and powers on and off the system. The setting selector button cycles through the five threshold settings. One LED indicates very little bump force needed and five LEDs indicate the highest setting, where a larger hit is needed to open the suspension. The controller is said to run between 16 and 20 hours before needing to be charged. We would say it’s closer to the 16-hour mark. A micro-USB port is used to charge the unit, and it takes about two hours.
DOWN AND DIRTY
The world of XC racing has been evolving, and World Cup courses are getting more demanding. That’s why it wasn’t a surprise that the Mach 4 SL is capable of being a great trail bike, too. This test bike with its 120mm fork offers a slightly wider range when it comes to trail selection and, let’s be honest, we don’t race World Cups. Ours also has the slightly beefier 34 stanchions, along with the added 20mm of travel for our local trails.
The drawback for us is the seat tube angle changes 1 degree, making it harder to adjust over the cranks. It also shortens up an already short 440mm reach on the 100mm version to 427mm. This means an even longer stem was in order. The wheelbase is short at 1150mm, which is something that I personally like, since I enjoy tight and technical trails; but, it pushes it a bit more to the XC side of things.
Thanks to the Live Valve, the suspension is very supportive but supple at the same time. The controller seamlessly opens the system if needed and allows the tires to stay on the ground with traction high. Big efforts don’t open the system, so even aggressive riders will enjoy the intelligence that Live Valve brings when climbing. Our bike stock is incredibly light at 24 pounds and is easy to flick around.
The system also works much differently when climbing and remains open for a very short duration. The controller will also open the front or rear suspension independently as needed. I like the controller in the three or four LED setting but was content as low as one LED (the most sensitive). I will say that the 110mm head tube with the 120mm fork positioned me very high, even with the stem as low as it could go for an XC bike.
When things transition to downhill, I’m torn. The bike is very confidence-inspiring, and I found myself riding it like a much longer-travel bike. The Live Valve works wonders as long as the trail has an imperfection to open the system. On flow trails or smooth sections, the suspension stays closed, and this can be unsettling. It’s that feeling you have when you crest a climb and head into the first downhill turn but forgot to unlock your suspension and drift into the first few sections. The difference is if your trail has a lot of these smooth sections, it keeps happening, and the only way to leave it unlocked is to turn the system off.
On trails that were super fast and smooth, I liked the most sensitive setting (one LED) because I was more likely to have the system open when I wanted it. On any other trail, I had no problem and could run any sensitivity with confidence. Another very cool feature is the free-fall sensor, meaning that any time the bike gets airborne, the suspension opens so landings are much plusher and more confident.
The suspension linkage works very well, even without the Live Valve. I did plenty of riding with the system off, and the bike was still supportive and efficient. Cornering is very fun; the bike goes where it’s pointed. Fast turns, tight turns and technical turns are opportunities where a few seconds can be made up.
MODS AND UPGRADES
I enjoyed the bike as is, but I would consider the 100mm fork for a more XC position. I think this would still offer great trail capabilities, but be much better in terms of positioning. The Live Valve system is remarkable but would work better with a different tire that has more to offer on the outside tread in case the controller delays opening heading into fast, smooth corners. I also would go slightly wider on the rim for the same reason, but this would probably add weight.
The biggest drawback for me as an endurance rider is that even with the new shock position, I can only fit one bottle. Sure, you can run a large bottle and it’s easy to get to, but I don’t like wearing a hydration pack on rides over six hours. Since the standover has been lowered, I added the SKS on the top tube, enabling an additional bottle cage. It didn’t look pretty but worked flawlessly.
At the end of the day, this XC bike is a bit more trail than the competition. This isn’t a downside; it just makes it a more versatile bike for most. The 120mm fork made it harder to fit for XC races, but gave it a slight advantage on more aggressive trails. The geometry and weight of the bike made it very playful and a blast to ride.
The Shimano XTR works flawlessly, and with a 34t front ring, I had plenty of range, even on slow, steep climbs. The two-piston calipers and 160mm rotors worked well, but I would consider a beefier system for the 120mm spec’ed bike. While Fox Live Valve is not feasible for most with its nearly $2000 premium, if it’s something you’re considering, go for it. If you try to upgrade later, it will set you back more than double that, so make up your mind before you buy.
At Leadville, the bike was complete overkill. For me, that’s better than being under-gunned and beat up. It let me maintain speed and makeup time on the descents while still being able to eat and drink. On the climbs, the weight wasn’t noticeable, but the added traction was key where traffic, rocks and oncoming riders would occasionally send you off line. I didn’t beat any records, but out of all my trips to the thin air of Leadville, I had the most fun and felt the best after the race.
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