Pivot Cycles Mach 4 SL first-ride review: Full XC race machine

Pivot Cycles has been on a bit of a roll lately, what with the Trail 429, Switchblade, Firebird 29, and Phoenix all receiving healthy doses of positive media and user reviews, plus healthy sales to match. But there’s been one category where the brand has been feeling a little off-the-back in recent years: cross-country. Pivot promises to remedy that now, however, with the release of the new Mach 4 SL, which will replace the long-running Mach 429SL as the company’s premier XC race bike.

First off, you’ll notice the name: it’s the Mach 4 SL, and not the 429. The original Mach 4 was shod with 26″ wheels, and when Pivot switched to a size-specific 29/27.5″ setup, that necessitated a badging change. But given how the XC market is now firmly in the 29er camp, Pivot decided to revert to the simpler Mach 4 moniker since wagon wheels are basically a given in that category these days.

Naturally, the new Mach 4 SL is made of carbon fiber, and also a given is the new bike’s 100mm of rear wheel travel, which continues on with a variant of the dw-link suspension layout that has marked every Pivot full-suspension bike since the inception of the company in 2007. It’s tuned more for pedaling efficiency than longer-travel Pivot models, of course, but it also differs in that the shock is now oriented vertically, tucked tightly in front of the seat tube instead of residing under the top tube as has always been the case with Pivot models.

Out back is yet another iteration of the dw-link rear suspension design that has adorned every Pivot full-suspension bike since the company was founded in 2007.

It’s also very light, it’s compatible with Fox’s incredible Live Valve electronic suspension, it’ll supposedly clear a 2.5″-wide Maxxis Minion out back, and the progressive geometry further blurs the lines between XC and trail with a longer and slacker front end, shorter chainstays, and a steeper seat tube angle.

Pivot will offer the Mach 4 SL as a bare frame for US$3,400 / AU$5,300 / £3,550 / €3,600, or in one of 22 complete build kits, ranging in price from US$5,000 / AU$8,000 / £5,250 / €6000 to US$11,300 / AU$18,000 / £11,800 / €13,550. Every Mach 4 SL gets the same carbon fiber frame, and at least for now, there’s no aluminum version. But, continuing a most-welcome trend, it’s actually available right now.

REAFFIRMING THE MACH 4 STORYLINE

The original Mach 4 was a distinct outlier when it was first introduced a dozen years ago. Although its 100mm of rear-wheel travel put it head-to-head with other cross-country bikes of the time, its ride and handling suggested that it was meant for much more than just going uphill fast. Subsequent Mach 4(29) models have followed suit, and this latest Mach 4 is no different with angles that focuses more on high-speed stability than low-speed, point-and-shoot agility.

Pivot will offer the Mach 4 SL with World Cup or Team build kits. The former is more race oriented, with 100mm-travel forks and fixed seatposts, while the latter comes with 120mm-travel forks and dropper posts.

Even when equipped in World Cup race trim with a 100mm-travel fork, the Mach 4 SL’s 68.5° head tube angle is the same as what Specialized uses on its more trail-oriented Epic Evo, which features a 120mm-travel fork. Nearly all Mach 4 SL complete builds will come with a 120mm-travel fork standard, though, which kicks the front out even more, down to 67.5° (which, somewhat remarkably, is nearly identical to Pivot’s much longer-travel Switchblade).

Chainstay length has also decreased substantially from the Mach 429 SL, from 445mm to a stubby 431mm, while the slightly longer reach dimensions are now borrowed from the current Trail 429. Bottom bracket height is the same as before, though, which is just fine since many already found it to be about as low as it could be without inducing too many pedal strikes. Seat tubes are steeper than before, but not outrageously so — it’s still a pedaling-intensive XC bike, after all.

Tube diameters on the Mach 4 SL are generally smaller than on other Pivot full-suspension frames, all in the name of saving precious weight.

Shorter riders will be happy to see that Pivot has added a long-overdue extra-small size (without having to switch to 27.5″ wheels), and Pivot says the five-size range will accommodate riders from 4’ 10″ all the way up to 6’ 7″. Clever repackaging of the rear shock — which is now oriented vertically instead of horizontally — means that even the smallest size has room for a large water bottle to fit inside the front triangle, while the XL size can handle two (and yes, there is a second set of mounts).

Standover clearance has improved across the board, too, and the shorter and straighter seat tubes used throughout allow for longer-travel dropped posts. Pivot only specs 150mm-travel posts on the XL size, but my suspicion is that many riders will be able to use those on other sizes, too, depending on saddle height.

YUP, IT’S LIGHT

Although the Mach 4 SL’s geometry paints it more as a trail bike, its showing at the scale is certainly more in keeping with the XC crowd. Claimed frame weight with the stock Fox Float EVOL rear shock is just 2,105g (4.64lb) — over 300g lighter than the old Mach 429SL for a given frame size, according to Pivot, and about 700g lighter than a Trail 429. Granted, that Mach 4 SL claimed figure is for an extra-small frame size, and while larger sizes will obviously be heavier, there usually isn’t a huge amount of variation as you move up (and at least Pivot’s claim includes paint, which is surprisingly heavy).

Claimed weight for a complete World Cup XTR build — in a medium size — is a paltry 9.48kg (20.9lb), without pedals.

While many companies are moving to fully guided internal routing, Pivot is sticking with bolt-on ports and open frame tubes. This makes it a little more of a hassle to get all of the lines to run through the frame, but it also affords more flexibility for different drivetrain and suspension setups.

A lot of that weight saving comes from the use of higher-stiffness carbon fiber, of course, along with Pivot’s “hollow core internal molding” technology, which uses semi-rigid internal pre-forms inside of the frame instead of the old-school inflatable bladders. However, the tubes themselves are also a fair bit smaller in diameter on the Mach 4 SL than what Pivot uses elsewhere, which cuts down on the amount of material required in the first place. Both the front and rear triangles are more compact that what Pivot has used in the past, too, which cuts down on the amount of material required further still.

Pivot says that additional weight savings came from that vertical rear shock placement. Since there are no longer any suspension loads being transferred into the top tube, that part could be made lighter — and since the bottom bracket area is already heavily reinforced, no weight had to be added there. In addition, all of the suspension pivot bearings now rest in seats that are molded directly into the frame with no additional aluminum required.

NO TO DI2, BUT YES TO LIVE VALVE

Pivot was one of the first companies to partner with Fox on its fancy Live Valve terrain-sensing electronic suspension system, so it’s no surprise to see that the system will be offered on the Mach 4 SL. Dedicated wiring ports are included for the fork sensor, rear dropout sensor, and controller/battery unit, and the latter is neatly tucked away underneath the top tube.

Inside the rear shock and fork are latching solenoids that can open and close the compression damper in just 3ms.

Upgrading to Live Valve adds an extra US$1,900 on top of the standard build kits, and adds about 220g (0.5lb). That’s a lot of money, but also a considerable saving over the US$3,200 it’d cost to add the system after the fact — plus, the folks at Pivot HQ in Arizona will route all of those wires for you.

Pivot was also one of the first companies to specifically develop mountain bike frames to accommodate Shimano Di2 electronic drivetrains. But like the Trail 429 that Pivot launched last year, you won’t find any compatible wiring ports or battery storage here. It’s widely expected that Shimano will release the second generation of that fancy electronic drivetrain sooner than later, but given the lack of wiring ports and the anticipated life cycle of this Mach 4 SL, Shimano is either moving to a wireless (or semi-wireless) format, or things are progressing slower than anticipated.

We’ll have to wait and see, but point being that if you’re already dedicated to Di2 and were hoping to use it here, you’ll have to get creative. And yes, drilling holes will most definitely void the ten-year frame warranty.

CLEARANCES, BB SHELLS, ROUTING — AND WHAT ABOUT SUPERBOOST?

Can’t stand the 157mm-wide SuperBoost Plus hub spacing that Pivot uses on so many of its other bikes? Well, since the Mach 4 SL is only meant to be ridden with 29″ wheels, Pivot has built the frame with plain ol’ regular 148mm-wide Boost hub spacing instead. That said, Pivot says there’s still enough room between the stays to clear 2.5″-wide Maxxis Minions while running chainrings up to 38T.

The rear hub uses standard Boost 148mm-wide spacing, but Pivot says the stays will still clear a 2.5in-wide Maxxis Minion tire.

Speaking of chainrings, Pivot is following the lead of the Trail 429 in that the Mach 4 SL is built solely for 1x drivetrains, which not only helps in terms of tire and drivetrain clearances, but allows for wider linkages and bearing spacing for a stiffer connection between the front and rear triangles. That 1x-specific layout even takes care of a long-standing criticism of several other Pivot frames: the loop of derailleur housing that dangles below the bottom bracket on the Trail 429 and Switchblade is finally gone, but the ISCG tabs stick around if you’d prefer the added security of a light-duty chain guide.

And speaking of bottom brackets, Pivot is sticking to its guns: the Mach 4 SL uses yet another PF92 press-fit shell. Before you crack out the torches and pitchforks, though, even I have to admit that Pivot seems to do a better job than most in terms of keeping the shell dimensions to proper tolerances. I still don’t like using a hammer when I have to install or remove a bottom bracket, but at least in my experience, press-fit seems to work as it’s supposed to on the Pivot frames I’ve ridden (and owned) over the years.

A second bottle mount is located on the underside of the down tube. The small hatch further back is similar to what Pivot includes on the Mach 5.5 model, but it isn’t for a Shimano Di2 battery. In this case, it just provides access to help mechanics feed the dropper seatpost line up into the seat tube.

Cable routing is internal throughout, using the same interchangeable port system found in other recent Pivot frames. Unfortunately, none of the lines are fully guided, but there are at least a fair number of sizable access holes to help fish things through, there’s a lot of flexibility in what can be run where, and the covers also lightly clamp the hoses, housings, and wires to keep rattling at bay.

And finally, from an aesthetic standpoint, let’s all maybe cheer the fact that the Mach 4 SL has been penned more with a ruler than a French curve, and that Pivot is sufficiently confident that it no longer feels the need to put a logo on every frame tube.

FIRST IMPRESSIONS

Press launches rarely provide a good opportunity to really get a proper feel for a bike, but Pivot conveniently chose to launch the Mach 4 SL in Fruita, Colorado, on trails that I not only know very well, but also happened to be on just three weeks prior. In typical fashion, Pivot put editors on one of the top-shelf builds, featuring Shimano’s new XTR group, Reynolds carbon wheels, and the complete Fox Live Valve system.

This was admittedly my first time on Live Valve, but to be perfectly honest, it’s ruined me.

Even without the Live Valve system turned on, the Pivot Mach 4 SL climbs with superb efficiency. Photo: Cody Wethington.

With the system turned on, the suspension is open and active when you want it to be, rigid when you don’t, and utterly settled and composed throughout with no other inputs required. There were also some unexpected benefits, such as incredible support on g-outs, and easier launches where you’d normally have to be more careful with your timing on the lip. You still need to exercise some care when it comes to matching the bump threshold setting to the ground type, but once that’s out of the way, Live Valve is essentially what the Specialized Epic aspires to be, without the clunkiness and occasional confusion.

That said, this is still a Pivot cross-country bike with a dw-link rear end, and it works extremely well even with Live Valve turned off. There’s minimal unwanted rear-end movement under power, excellent (albeit somewhat firm) bump control, and very good support throughout the range of travel, just with a slightly busier ride quality and more input required when approaching certain obstacles.

The 100mm of rear wheel travel says “XC bike”, but the progressive geometry encourages you to run the Mach 4 SL harder than you might otherwise expect to do on a pure race bike. Photo: Cody Wethington.

Frame stiffness isn’t quite like what you’d find on a Switchblade — or a burlier trail or enduro bike, in general — but it certainly seems competitive for the category, and balanced from front to rear. And the geometry feels spot-on, at least for the faster trails where we rode: stable and composed at high speed, but nimble enough for rapid-fire turns without requiring too much handlebar wrestling.

For now, my biggest criticisms lie with a couple of spec items.

Pivot includes 29×2.25″ Maxxis Aspens front and rear on the more race-oriented World Cup builds, and the 29×2.2″ Maxxis Ardent Race for the somewhat more versatile Team variants. They’re light and fast-rolling, no doubt, but the extremely low-profile tread designs aren’t the best for general trail riding. For the dry-and-dusty trail where I live, I’d like to see something slighter meatier, at least up front. Likewise, all Mach 4 SLs come with 160mm-diameter rotors front and rear, instead of a more useful 180/160mm combo.

Team builds come with 29×2.2in Maxxis Ardent Race tires, while World Cup builds come with 29×2.25in Maxxis Aspens. Both are very fast-rolling treads that sacrifice grip for low rolling resistance.

Given how capable the Mach 4 SL chassis feels, both of those seem like limiting factors for what otherwise seems like a worthy opponent to the Yeti SB100. Granted, the argument can easily be made that the Mach 4 SL is supposed to be a race bike, and should be equipped as such. However, I’d argue that there are far more people who just want a fast and capable bike than ones who will specifically be buying this to race.

Either way, stay tuned for a more in-depth review once we’ve got a production sample in hand, and more saddle time on local trails.

www.pivotcycles.com

The new Mach 4 SL is Pivot’s lightest cross-country bike to date, but yet its geometry makes it feel more like a shorter-travel trail machine.

Moving the rear shock to a vertical orientation just in front of the seat tube left enough room in the front triangle for a large-sized water bottle, even on the extra-small size.

Bearing seats for the suspension pivots are now molded directly into the carbon fiber whenever possible. The two suspension links are made of aluminum, and comprise the vast majority of the non-carbon weight on the Mach 4 SL frame.

A small rubberized flap keeps small rocks and debris from getting jammed in between the lower link and the carbon frame.

The new Mach 4 SL is designed specifically for 1x drivetrains, which allowed for wider suspension links, wider bearing spacing, and neater routing for the rear derailleur housing.

Pivot is sticking to the PF92 bottom bracket, and that wide format allows plenty of room for suspension hardware.

Seat tubes are notably short (and straight) across the board, which should allow most users to run 150mm-travel dropper seatposts.

Standard tooled rear axles leave a mostly flush finish.

Since the chainstay no longer has to clear a front derailleur cage, Pivot positions it higher up so it can take a more direct path from end to end, saving weight and increasing stiffness. Chain slap could be an issue at that point, but between the clutched rear derailleur and the molded cover on the frame, things run pretty silently.

Fox Live Valve is an option across the board on the Mach 4 SL, and it’s absolutely incredible on the trail. That said, there’s still some time required to get the initial setup how you want it.

Fox Live Valve requires two accelerometers to feed information to the system’s controller: one at the fork, and another at the rear axle.

While the fork sensor is a bolt-on bit that works with any current Fox fork, the rear Live Valve sensor requires dedicated frame fittings.

Pivot tucks the Live Valve controller and battery underneath the top tube, where the buttons are still readily accessible, but the flashing lights aren’t right in the rider’s field of view.

Fox claims 20-40 hours of ride time on a fully charged Live Valve battery. Five preset modes are available, too, each with progressively harder hits required to open up the compression valves.

The stock handlebar is 740-760mm wide, depending on build kit. Either way, the ends are cut at an angle to work with WTB’s PadLoc grip system.

The carbon wheels feature rims made by Reynolds.

The color schemes may not be particularly imaginative, but at least they’re clean and understated. Photo: Pivot Cycles.

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