Wil reviews the brand new Pivot Mach 4 SL
The Mach 4 SL debuts in 2019 as a freshly baked model for Pivot Cycles. With a sleek carbon fibre frame, 29in wheels and 100mm of efficient dw-link suspension, it slots into the Pivot lineup as the flagship full suspension XC race bike.
In some regards, it’s actually an amalgamation of two existing Pivot models; the Mach 429 SL and Mach 4 Carbon – two very popular bikes on the privateer race circuit. Compared to those two bikes, the Mach 4 SL is lighter, with a more compact suspension package and modernised geometry that’s inspired by the Trail 429.
Labelled as a ‘gravity defying rocket ship’, the Mach 4 SL is purportedly the lightest and fastest full suspension bike that Pivot Cycles has ever produced.
Big Wheels Only Club
Firstly, the Mach 4 SL is rolling exclusively on 29in wheels. Given how popular the 27.5in Mach 4 Carbon has been (especially in the XS and S frame sizes), this is a pretty bold move.
Pivot is confident in its decision though, particularly because the Mach 4 SL will be offered down to an XS size – something that wasn’t possible with the previous Mach 429 SL. And how’s this – there’s actually more standover clearance in the new XS frame than there was with the 27.5in bike.
In order to lower the top tube and accommodate riders as short as 4’10” (150cm), Pivot has flipped the shock to a vertical position. It still uses a dw-link suspension design, with two small machined alloy links connecting the one-piece carbon swingarm to the mainframe via Enduro Max sealed cartridge bearings. Pivot says the overall behaviour isn’t all that different, but with the shock mounting at the bottom bracket instead, the mainframe can be made more compact.
Even with the lowered top tube though, each frame size – including the XS – will accommodate a full size water bottle inside the mainframe. And you can bolt one underneath the downtube too. Those endowed with extra long pins will be pleased to know that the XL frame will actually take two medium bottles inside the frame.
As a proof of concept, Pivot had both 27.5in and 29in alloy prototypes welded up in its Phoenix-based R&D facility. These were both built in an XS size for Chole Woodruff – an American XC racer, and one of Pivot’s sponsored athletes who played a big role in the Mach 4 SL’s development process.
While Chloe has enjoyed plenty of success on her much-loved Mach 4 Carbon, there have been times during World Cup races where she’s felt at a disadvantage to those on 29ers. However, at 5’2” (1.58m) tall, she wasn’t able to fit onto the Mach 429 SL.
On top of this, development of lightweight 27.5in components, including wheels, tyres and forks, is slowing down significantly. Going forward, this will severely limit choices for XC racers who need them for different courses and conditions.
With the new Mach 4 SL though, Chloe was able to get the standover clearance she needed, along with that crucial water bottle clearance. And once Chloe was happy with the handling and fit of her prototype, Pivot decided to fully commit to the big wheels.
High-Tech Carbon Frame
As well as being more compact, the new Mach 4 SL frame is also lighter. Slimmer and straighter tube profiles replace the swoopy-droopy look of previous models, and frame weight drops down to just 2105g for the XS size with shock. That’s over 300g lighter than the Mach 429 SL, and 225g lighter than the Mach 4 Carbon.
There’s less alloy bonded into the frame, with both the headset and pivot bearings now pressing in directly. Having co-developed the press-fit BB standard with Shimano over a decade ago, Pivot continues on with a huge 92mm wide shell on the Mach 4 SL. Despite many UK riders’ disdain for press-fit BBs, Pivot remains confident in its execution, stating that it manufactures the BB shell to an even higher tolerance than the head tube. Complete bikes come spec’d with a high quality Enduro bottom bracket with alloy press-fit cups.
The Mach 4 SL’s swingarm is more compact than its predecessors, with the slender tubing and bolt-up 148x12mm rear axle ensuring a narrow profile for sneaking through tight rock gaps. No, there’s no Super Boost Plus 157x12mm hub spacing here, since the Mach 4 SL is a dedicated 29in race bike. There is no provision for 27.5+ wheels as with Pivot’s Trail 429, Switchblade and Firebird 29 models.
Since the frame is 1x specific, the drive-side chainstay now takes a more direct route from the lower pivot to the rear axle, which makes it lighter and stiffer. Double uprights on the swingarm also increase rigidity.
There’s plenty of heel clearance, despite there being room to run a World Cup-able 38t chainring. Oh and for those wondering, Pivot says a 2.5in Minion DHF will fit in the back. With the more conservatively-sized 2.2in Ardent Race tyres on our test bikes, there’s loads of mud room. Pivot has also added a neat rubber shield over the lower dw-link to keep rocks and debris from working into tight gaps.
As you’d expect, the Mach 4 SL gets full internal cable routing via the Cable Port system. Unbolting the ports reveals a large hole to poke cables in and out of, and they can be pulled taut before being bolted back down to keep everything snug and slap-free.
Given Pivot’s previous embrace of Di2, it’s surprising to see the Mach 4 SL skip Di2 compatibility. According to Pivot’s CEO, Chris Cocalis, they’re still yet to hear any concrete plans from Shimano regarding future electronic MTB drivetrains. Top-end builds will be available with SRAM’s wireless AXS drivetrain though.
New-School XC Geometry
Inspired by the latest Trail 429, the Mach 4 SL brings a contemporary approach to its geometry.
Depending on your preferred flavour, the frame will take a 100-120mm travel fork with a 44mm offset. Most builds come with a 120mm travel Fox 34 Step-Cast, while the super high-end ‘World Cup’ models come spec’d with a 100mm travel Fox 32 Step-Cast fork. For more information on the various build kit options and pricing, check out the news story here.
On the note of the World Cup model, I did manage to weigh a Medium bike at the launch, which was outfitted with the XTR build kit, a carbon seatpost, a lighter bar & stem, and the regular cable-activated suspension package. The weight? Just 9.47kg (20.9lbs) without pedals. Hot damn.
With the bigger fork option, the head angle sits at 67.5° and the effective seat angle at 73.5°. The reach is actually identical to the Trail 429, sitting at 427mm on my Medium test bike. It’s worth noting that reach increases to a roomy 440mm with the shorter travel fork though, which is identical to the Santa Cruz Blur I’ve been testing lately.
Compared to the 429 SL, the new Mach 4 SL’s rear centre length is much shorter at 431mm (down from 446mm). However, the overall wheelbase length has grown significantly – on my Medium test bike it increases from 1121mm to 1146mm.
Also of note is the short and straight seat tube, which offers a usable insertion depth for longer stroke droppers. My medium bike came with a 125mm Fox Transfer, but I could easily bump up to 150-160mm travel.
Fox Live Valve
Pivot Cycles has worked closely with Fox Racing Shox on its Live Valve suspension system, and the Mach 4 SL features full integration for the rear sensor, internal wiring, and the control unit.
Each spec level will be available with a Live Valve upgrade, which comes with both increased cost (it’s a £1,950 / $3,000 AUD up-charge) and weight (around 200g).
If you’re not familiar with Live Valve, you should definitely check out Chipps’ detailed ride report.
In a nutshell, it’s a system that offers automated, electronically-controlled damping for both the fork and shock. Instead of the rider having to toggle handlebar remotes and lockout levers, the system does all the work for you, with the key goal being improved rider efficiency.
Three sensors (one on the back of the fork arch, one in the control unit, and one near the rear brake) measure incoming bump forces, and the on-board computer determines whether the suspension should be open or closed. Additionally, a 3-axis accelerometer works out if the bike is climbing, descending, on flat terrain, or in the air, and the decisions it makes are influenced accordingly.
The response rate is fast. The sensors read inputs 1000 times per second, and the damping can switch from open to closed in 3 milliseconds. According to Fox, the control unit will make on average around 480 mode changes per hour of XC racing.
All of the internal settings are predetermined by Pivot and Fox. The ‘Closed’ setting isn’t quite a full lockout, but it’s a relatively firm compression setting. In comparison, the ‘Open’ setting is about as plush as you can get given the Mach 4 SL’s minimal travel. You can adjust the Open setting with a 3mm hex-key, which offers 18 clicks of low-speed compression damping from full plush (0) to full firm (18). Due to the added efficiency the Live Valve system brings to the table, Fox recommends leaving the LSC setting in the plushest setting.
You can also adjust the sensitivity of the system via buttons on the battery pack. There’s an on/off button, and a mode button that will first display the battery life, followed by the sensitivity setting. ‘1’ is the most sensitive setting, meaning the suspension will open up more easily. ‘5’ is the least sensitive, so the suspension will remain in the Closed setting for longer.
Everything is waterproof to the IPX7 rating, and the system uses plug-in wires for the fastest response rate and low energy consumption. Battery runtime varies between 20-40 hours, depending on how rough the terrain is and what setting you’re running. A full charge takes two hours, though a 15 minute panic-charge will give you an hour of trail use. If the battery does die on you though, the fork and shock will thankfully switch to the full open setting.
Setting Up Live Valve
Being my first experience with Live Valve, setup was initially intimidating. Despite the system’s inherent complexity though, it’s actually pretty simple to use.
To set sag, you switch the whole thing off. For my 70kg riding weight, I ran the fork with 80psi and two volume spacers inside the air spring, and set the rebound two clicks slower than halfway (8/20 clicks).
The Live Valve shock gets a medium compression and rebound tune from the factory, and comes fitted with the largest possible volume spacer. Pivot adds a convenient clip-on sag indicator to help with setup, and to hit the desired 30% sag figure, I had 177psi inside the air chamber.
The partially hidden rebound dial is a pain to adjust, as you’ll need a small hex key to reach the machined notches within. Once you get it set you won’t really have to touch it again though. I settled on bang-on halfway, with 10/20 clicks of rebound damping.
To test out the new Mach 4 SL, Pivot invited me and a handful of other journos all the way out to Fruita in Colorado. We clocked up 130km of riding over the three day launch, which gave me plenty of saddle time to get to know the bike intimately.
The first two days took us around the 18 Road and Kokopelli trail networks, with a range of riding that varied from smooth, hardpacked bermy singletrack, through to slabby and highly technical rock crawling. The riding around Kokopelli in particular was picturesque, but quite rough. If I was choosing a bike to ride there, I’d likely opt for something like a Mach 5.5 or Trail 429.
Before our tyres had even touched the dirt though, they’d gone through a rigorous setup process based off of our provided measurements and preferences.
The fork and shock pressures I mentioned earlier were exactly what Pivot had calculated based on my riding weight. Likewise, the tyres had been set to 22psi on the front, and 25psi on the rear. Even the saddle height was spot-on.
For my bike, the stock 75mm stem had been swapped for a shorter 60mm length, which worked beautifully with the 740mm wide riser bars. Future bikes will be coming with a new 760mm wide carbon flat bar though.
I’m not particularly fond of the stock Pivot PadLoc grips and their honeycomb tread pattern, so it was good to see several other pairs to choose from. I ended up selecting a thinner and smoother-profile WTB Commander grip. These still have the squishy wedged PadLoc ends, which aside from being quite comfortable, also add a little extra width to broaden the bars out to 755mm.
All of this might not sound important, but it’s worth mentioning given that this sort of emphasis on setup doesn’t always happen at bike launches. Pivot CEO, Chris Cocalis is well-known for his fastidious attention to detail when it comes to engineering bikes, and this focus extends through to bike setup too – something that Pivot aims to get dialled with its public demo fleet. He shrugged it off as nothing special when I asked him about it, responding; “you only get one chance at a first impression”.
Consequently, with all this pre-faff sorted out, the bike was immediately comfortable. Aside from a tweak to the saddle tilt, I didn’t have to touch anything for the rest of the launch.
Riding The Pivot Mach 4 SL
With the carbon frameset, high-end DT Swiss wheels and speedy tubeless tyres, the Mach 4 SL isn’t exactly being held back in the rolling speed department. My test bike weighed in at 11.37kg (25lb), and it feels every bit that light on the trail.
On the first two days of riding, I spent a good amount of time messing around with the Live Valve settings. I tried the middle (3) setting first, then the firmest (5) and softest (1) settings, and I also rode with the whole thing switched off too.
This was important for me to experience, as I don’t expect the lion’s share of Mach 4 SL sales to feature Live Valve suspension, given just how expensive it is.
The good news though is that even without any Live Valve sorcery, the Mach 4 SL is still a very efficient pedalling bike.
The dw-link design provides a familiar level of anti-squat with excellent power transfer, providing you’re not mashing out of the saddle. It manages to deliver this support while also maintaining usable traction levels though. And along with the light overall weight and decent volume tyres, the Mach 4 SL asserts itself as a naturally gifted technical climber with superb drive.
While the rear suspension is effective, it is more XC-firm rather than trail-bike plush. However, there’s a real air of consistency to the rear travel, which is impressive given there’s only 100mm of it.
The support discreetly ramps up towards the end, and despite me maxing out the 40mm stroke shock regularly, I can’t say I ever detected a clunky bottom-out. That’s a difficult trick to pull on such a short travel bike, but Pivot has nailed it on the Mach 4 SL. It’s a smooth operator indeed.
During our time on the unfamiliar-to-me Kokopelli trail network, I encountered surprise-drops and mid-descent rock strikes with alarming regularity. It’s telling of the Mach 4 SL’s capabilities that I never once went OTB or really crashed at all, despite using up every last millimetre of travel on both the bike and my limbs.
The stiff chassis and compliant wheels certainly help, but I think the biggest, and most pleasantly surprising contributor, is the Mach 4 SL’s competent handling.
With the 67.5° head angle and 44mm fork offset, there’s a usable amount of trail up front that helps to steady the front wheel on the descents. This gives the Mach 4 SL welcome stability when the trail points downhill and gets really rough. Even at speed on foreign terrain, I was coaxed into staying off the brakes for longer thanks to the bike’s unfazed demeanour.
I was also glad for the slightly shorter stem, which helped me to get my weight back when I hadn’t committed to a full drop-off, and was attempting to, err, casually roll through it.
The 60mm stem also helped to increase leverage over the front wheel, which meant I wasn’t forced to wrestle the bike through the really twisty stuff. Far from it really. Along with the short chainstays and responsive suspension, the Mach 4 SL proved to be every bit as lively and rippable as some of the best trail bikes I’ve ridden.
Throw in the lower weight and zippy wheels though, and it’s just that bit more vibrant and engaging to ride.
Racing The Grand Junction Off-Road
For the third day of the launch, we were to be competing in the Grand Junction Off-Road event, just down the highway from Fruita. As part of the Epic Ride series (which includes the 24-hours in the Old Pueblo), the Grand Junction Off-Road offers 15, 30 and 40-mile race options.
Somewhat ambitiously, I’d entered into the 40 mile category along with four others.
According to the GPS profile, the race actually ended up being 70km long with over 1800m of climbing. It took me four hours and 18 minutes to complete, which somehow put me in pole position for the Journo Cup™.
The race itself was both one of the hardest and most rewarding rides I’ve ever done.
It was a total beatdown on both the body and the bike, with some properly gnarly and technical terrain making up the singletrack sections both at the start and towards the end of the course. The middle section comprised of two horrible climbs – one up the super steep Windmill road, and the other up a slick rock section filled with awkward slabby step-ups that I did not need at that point in the race. There was a good hour in there where I largely rode on my own, while my mind drifted to a darker place.
For the race, I set my Live Valve controller on setting two after much discussion within the group. Given there was going to be a healthy amount of bitumen and fireroad throughout the race course, so I wanted the extra efficiency wherever possible, without the suspension being so firm as to be uncomfortable deeper into the course.
In this racing application, Live Valve makes complete sense. While the Mach 4 SL isn’t exactly a poor pedalling bike, if you’re out of the saddle, it will oscillate up and down – like most bikes do. With Live Valve working its magic though, you can properly stomp on the pedals like a hack, and the bike will stand to attention as if it’s basically rigid.
Even with your bodyweight shifting all over the place, the fork and shock stay sufficiently firm. This does dissipate somewhat in setting 1, which is a little too easy to overwhelm when you’re mashing. I’d say setting 2-3 will suit technical race scenarios, while setting 4-5 are more useful for groomed singletrack.
With the added zip, riding the Mach 4 SL with Live Valve engaged encourages a more aggressive riding style. As well as putting more power to the rear wheel, I also found the firm compression setting to work wonders through high-speed corners. The fork in particular sits higher in its travel, which keeps the head angle and trail consistent for a noticeably more direct and squirrel-free feel.
The only issue I had was in the middle of the race, where riding at slower speeds along blown-out fireroads proved to be insufficient to trigger the Live Valve controllers. This meant I copped more feedback through the bike, which resulted in more fatigue. I would have turned the system off, but I was so exhausted at that point, I was afraid that if I dismounted, I might not get back on the bike.
I did wonder whether a handlebar remote could be useful to change between settings. But then the whole point of Live Valve is that its automated and there isn’t an extra wire or cable up at the cockpit. It keeps the bars clean, and it also frees your brain to stop worrying about constantly flicking levers, so it can focus on the riding ahead.
Even if that means a slightly bumpier ride sometimes, it’s made up for the fact that you have fully automated efficiency when you need it.
Once into the last 20km of technical singletrack descending, I caught my second wind and started to pin the bike a little harder. There was some really rough terrain in the last part of the course, and the Mach 4 SL conducted a gallant performance in trail bashery as we popped, swerved, and blasted down the mountain.
On the repeated high-speed chop, the suspension was open and effective, and the Live Valve’s behaviour is undetectable. This is because each time the suspension opens up, a timer is started and the system will remain open for a couple of seconds. If you hit another bump, the timer resets. When this happens while you’re riding downhill (considered a slope of 6.5° or more), the delay is made longer. Additionally, the accelerometers can also detect free-fall, and whenever this happens, the mode switches to Open to absorb the landing.
In an effort to make up time on the descent, I didn’t hold back on the Mach 4 SL. Despite absolutely smashing the tyres and rims, and hearing them bottom out a few times, I somehow avoided any punctures. I was genuinely worried I’d broken a rim on a couple of particularly raw hits, but the DT wheels remained unscathed. Impressive.
Is Live Valve Worth It?
While this is meant a review of Pivot’s Mach 4 SL, I feel like this is a question I can answer after the time I spent with the Live Valve system.
If you’re a competitive XC and marathon racer, then there are benefits to Live Valve. It boosts efficiency and encourages you to ride more aggressively, and that can be advantageous in racing scenarios. Chloe Woodruff and the rest of the Pivot XC team will be using Live Valve on the race circuit, and the Giant Off-Road Factory Race Team is also using Live Valve on the Anthem 29er.
For general trail riding though, it’s less beneficial – particularly on something that’s as inherently efficient as the Mach 4 SL. Perhaps I’d notice a bigger benefit on a bike with poor pedalling manners.
On that note, it would be interesting to see a bike developed 100% around the Live Valve system. Given the high point of entry though, and the fact that many consumers perceive it as something of a ‘bandaid’ for poor pedalling performance, that might be too risky for most brands.
Straight-up, this Pivot Mach 4 SL might just be the best XC bike I’ve ridden. It’s lightweight, efficient and stiff of course, but it was really the effective suspension and competent handling that impressed me most. I got away with a lot more on this bike than I probably should have.
It is also a bonkers expensive bike though. Whether the premium sticker price is worth it over bigger mass-produced brands will depend on how much value you place on the effective dw-link suspension system, and the high quality frame’s attention to detail.
One thing’s for sure though – if this is where XC bikes are going, then the future is very bright.
Pivot Cycles Mach 4 SL Team XTR
- Frame // Hollowbox Carbon Fibre, 100mm Travel
- Fork // Fox 34 Step-Cast Live Valve, Factory Series, 44mm Offset, 120mm Travel
- Shock // Fox Live Valve, Factory Series, 190x40mm
- Hubs // DT Swiss XRC 1200, 36pt Engagement
- Rims // DT Swiss XRC 1200, 28h, 25mm Internal Rim Width
- Tyres // Maxxis Ardent Race EXO TR, 120tpi, 2.25in Front & Rear
- Chainset // Race Face Next SL, 34t Chainring
- Rear Mech // Shimano XTR, 12-Speed
- Shifter // Shimano XTR, 12-Speed
- Cassette // Shimano XTR, 10-51t, 12-Speed
- Brakes // Shimano XTR Race, 160mm Front & Rear Ice Tech Rotors
- Bar // Phoenix Team Low-Rise Carbon, 35mm Diameter, 740mm Wide
- Stem // Phoenix Team XC/Trail, 35mm Diameter, 60mm Long
- Grips // WTB Padloc, 30mm Diameter
- Seatpost // Fox Transfer, 30.9mm, 125mm Travel
- Saddle // Phoenix WTB Team Volt
- Size Tested // Medium
- Sizes Available // Extra Small, Small, Medium, Large & Extra Large
- Weight // 11.37kg / 25.01 lbs
- RRP // £10,750 / $15,999 AUD
Wil’s flights & accommodation for this trip were covered by Pivot Cycles.
|Mach 4 SL Team XTR
|Upgrade Bikes, upgradebikes.co.uk
|£10,750 / $15,999 AUD
|by Wil Barrett for 3 days