At a Glance
There is a lot of hype surrounding the new wave of XC bikes that have arrived in the last twelve months. These short travel, lightweight and capable bikes may yet spawn their own genre but for the time being, we are seeing a response to more taxing World Cup courses and the application of kit that can be both light and strong.Buy XC Bikes on
Pivot launches their new Mach 4 SL, which is their unapologetically race-focused machine with 100mm of travel. The layout is different, but the DW link remains and it's brought right in line with the current Pivot sizing spectrum. The builds available on the Mach 4 SL are many, but they range from full-xc focussed race setups with a fixed post (remember them?) and 100mm fork to marginally more relaxed approach with a dropper and a 120mm step cast fork.
In our case, we have the latter end of the spectrum with something more akin to a trail bike but would happily smash out some racing in the form of a BC bike race for example. This model is the 'Team XTR' it gets the 120mm Fox 34 Step-Cast fork and the whole system is run on Fox Live Valve, which controls the damping via an electric system that senses forces on the bike and applies damping accordingly.
Full XTR (nearly) deals with drive and braking, the brakes being the lighter weight options with tiny little 160mm rotors and single pot discs. The drivetrain now has the 12-speed range and goes up to a 51 tooth ring on the cassette. A Fox Transfer is another nod to a more capable bike but the 75mm stem then confuses things. Ardent race tyres again suggest a rapid bike, but not so rapid that you're willing to have tissue paper sidewalls.
The frame is a thing of beauty, being a smooth, aesthetically pleasing carbon machine. Internal routing and plenty of bottle cage mounts are all nice touches on this high-end frame. The head angle on this model with the 120mm forks is 67.5 and the reach on my XL is 472mm. The chainstays are super short at 431mm but surprisingly the Mach 4 doesn't get super-boost plus and remains as 'standard' boost. The seat angle sits at 73.5 effective, which certainly isn't down with modern trends.
The Team XTR is an eye-watering $10,399.00, but there are models at a more reasonable price.
On The Trail
This is a serious tech-heavy bike, with Fox Live and full XTR there was a lot to get my head around. However, despite the electronic wizardry on board, set up is easy and the Live system only requires you to set the sag and switch it on.
Once set up, the Mach 4 SL shows it's hand quickly, and then proceeds to do everything else with similar speed, proving itself to be rocket ship of the highest order. There is a tension about the Mach 4 which makes sense as soon as the pedals are pushed and it lurches forward with impatience. This is in essence what the bike is all about, propelling you forward as fast as possible.
Climbing on steady inclines is phenomenal as the efficiency gives an ebike-like kick for every pedal stroke. The Fox Live system firms up under pedalling and any stomping out of the saddle is rewarded with a firm platform to transfer every last drop of power. With both front and rear shocks controlled as one system, there is always a firmness to putting the power down and the bike just fires itself down the trail.
On more technical climbing the Mach 4 SL requires a turbo boost approach where speed is applied out of the saddle to get over technical sections before regrouping and attacking the next. With a 73-degree seat angle, short stays and an XL frame with a high seat, the front does not like to stay on target whilst sat down. This was surprising, but for a racer, they're not going to be sitting down on a steep climb so I suppose it doesn't matter. For those of us that like to winch up in a seated position, the Mach 4 will argue against that vehemently, encouraging you to stop being lazy and stand up. The 75mm downturned stem did help, but it's all about the weight being too far over the rear axle, it's clear that no lazy enduro winching is allowed here.
While the seat angle may not be cutting edge, the Mach 4 gets a good head angle, a low bottom bracket and as such carves turns with confidence. As a singletrack slayer, it's a great bike, but this is a modern XC bike and can punch way above its weight. With a shorter stem and a grippier front tyre, the performance opens up no end and descents are no longer survived before the next climb, they are attacked full throttle.
The style of attack is perhaps a little different to an Enduro sled, but with superb power in the pedals, even the most leisurely of gradients can be approached at breakneck speed. Through rooty turns, the limited travel works hard to keep traction and the truly awesome 34 forks are stiff and precise. The rear end struggles to match, but it is a mere 100mm and asking too much from it would feel unfair. Although confident, there is a fine line to be trodden between pushing hard and finding the limits of the bike. This creates an engaging and exciting ride on even the most mellow of trails that would be dumbed down by a bigger bike.
The Fox Live element is pretty incredible, and I can see why racers will appreciate the system more than anyone else. Essentially it gives an excellent pedalling platform whenever you want it, without flicking a switch or lever. Come out of a corner and need to sprint? It's ready and waiting, and not just the back end, the front firms and it is all systems go. Fly off a drop? It all opens up and your return to earth is smooth and composed.
I did find it a little confusing when pumping terrain and needed to reduce the sensitivity a little (there are 5 settings) as I couldn't tell exactly what the fork was going to do and it felt unnerving. With it set up in a more relaxed way, in which it is fully open more often we got on better and it was more predictable.
Not being much of an XC racer, I ran it a fair amount without the Live Valve switched on and it's fair to say it very noticeable. It's also fair to say it still works great when it's all open unless you need that pedalling firmness then it's not something you'll be desperate for on your next bike. It's nice to know the Mach 4 is good even with analogue suspension!
With a 40mm stem on and a spikey front tyre, the capabilities are far more trail-bike like. Pivots Mach 429 Trail maybe their fun, short travel bike, but I felt that Pivot missed a trick I not having a more trail specced version of the Mach 4 SL. With a quick cockpit, tyre and brake tweak, the bike is transformed into the fastest and lightest trail bike I've ever ridden.
Shimano's new XTR needs a mention as the shifting has been impeccable and shows that the traditional drivetrain has once again been improved. Shifting under power is brilliant and the lever feel is typically Shimano, both subtle and precise at the same time. The brakes again are lovely to use, but lack power in the one pot and 160mm rotor set up. Again if you want a 'trail' Mach 4, bigger brakes are certainly needed.
As much as I've tried to encourage this bike to get outside the tape and ride some trails, it still has racing at its core. It's a testament to a great bike design that a few component tweaks can take a bike from the racecourse to the backcountry so easily. It's either an XC bike that likes to get gnarly on the side or a trail bike that loves to race, essentially it's the rider who will decide.
The Mach 4 SL proves that you can have a thoroughbred race machine that can attack trails with confidence, style and mind-boggling speed. Although aimed at racing, the Mach 4 SL is far more versatile and capable than it's cross country label would suggest.
This review was in Issue 60 of IMB.For more information visit Pivot Cycles
By Ewen TurnerEwen Turner is a self-confessed bike geek from Kendal in the Lake District of England. He runs a coaching and guiding business up there and has a plethora of knowledge about bikes with an analytical approach to testing. His passion for bicycles is infectious, and he’s a ripper on the trails who prefers to fit his working life around his time on the bike.