On test: Pivot Cycles Mach 4, October 29, 2008

Stout enduro racer

The Pivot Cycles Mach 4

Cyclingnews technical editor James Huang builds up a Pivot Cycles Mach 4 and finds it to be a stiff, agile and bulletproof cross-country performer with excellent suspension manners … and perhaps in need of a modest diet.

Pivot Cycles' Mach 4 is somewhat of an odd beast on paper. While its short 100mm of rear wheel travel and quick cross-country geometry scream, 'race me!', its surprisingly weighty showing at the scale is more in keeping with longer-legged trail bikes.

Indeed, our medium-sized Mach 4 bare frame falls on the wrong side of the 2.8kg (6.2lb) mark (with shock, seat collar and derailleur hanger) but at least the extra mass has been put to good use as the triple-butted 6000-series aluminum frame is one of the stiffest short-travel platforms we've tested in recent memory regardless of material.

The bottom bracket area is particularly well bolstered being designed around Shimano's new press-fit bearing cups and wearing a healthy 90mm width as a result. Pivot takes full advantage of the extra real estate with a monstrously broad, ovalized and even slightly asymmetric down tube at one end and a unique wide-set split seat tube design that straddles the eight-bearing lower suspension link at the other.

The multi-shape top tube and internal-type head tube are similarly beefy in dimension and the oversized seat tube is even bolstered up top by a small cross member. Flex? Sorry, you won't find any here.

Our Mach 4 tester arrived as a bare frame so we built it up with an intelligent (and mostly familiar) mix of light-yet-durable components of our own choosing. Total weight came to 11.53kg (25.42lb), complete with a pair of Shimano XTR pedals.

Weight? What weight?

The upper link is carbon fiber

The Continental Mountain King 2.4

Easton's Monkeylite SL riser bar

The Hayes Stroker Carbon features a handy tool-free reach adjust dial.

As compared to earlier Hayes brakes,

Thankfully for Pivot, the Mach 4 nails just about every other performance metric though and it feels markedly lighter on the trail than its somewhat disappointing numbers would suggest.

The frame's bomber overall stiffness translates into nary a hint of out-of-plane movement when out of the saddle and pushing hard and both wheels stay faithfully in their intended direction even when pinballing through a field of boulders or flying across off-axis roots. Other 4" bikes are certainly lighter than the Mach 4 but few feel this solid and predictable underfoot.

Likewise, the Mach 4's dw-link rear end yields a surprisingly capable ascender with a firm and efficient overall feel. Lay down the power and the Pivot rewards you with very good overall response and the otherwise unflappable climbing performance is only slightly sullied by just a hint of feedback when climbing in the granny on technical terrain. Though we wouldn't say the Pivot is quite hardtail-quick when you drop the hammer, it's still one of the sprightlier full-suspension designs out there and we rarely felt the need to flick the ProPedal lever on the included Fox RP23 rear shock.

Bump performance was simply superb with well-tuned shock rates and excellent trail feel throughout the travel range that is neither too isolating nor too harsh provided you put in the necessary time to dial in the somewhat sensitive shock pressure. Small impacts are faithfully erased, bigger hits are swallowed up in a manner that belies the Mach 4's modest rear wheel travel, and square-edged impacts that can often disrupt lesser designs are competently evened out without impeding forward motion. Not to be overlooked, either, is the fact that the Pivot manages to do all this with utter silence.

If all of this makes the Mach 4 sound more like a short-travel trail bike, that's because that's pretty much what it is and also how we ended up using it most. In one instance in particular, we easily kept pace with (and even caught) an experienced riding partner who was on what should have been a much faster 6"-travel machine as we descended back to the vehicles coming out of Colorado's Kenosha Pass trail.

Even so, the Mach 4 is still a capable race rig as we discovered during the recent 24 Hours of Moab. Time lost on the climbs was due almost entirely to lack of fitness which we dutifully made up by bombing the technical and unrelentingly rocky descents, especially during night laps. We intentionally made no efforts to go easy on our tester during any of our four laps (sorry, Chris) yet the only maintenance required in between was some occasional chain lube.

In Pivot's defense, some of the Mach 4's heft is offset by its integrated componentry. The press-fit bottom bracket cups save a handful of grams as does the chain-tracking (and excellent shifting) direct mount front derailleur but still, the Mach 4 strikes us as a tad overbuilt and could stand to lose a good hunk of mass to make it a little more appealing.

Pivot has also introduced a new SL Carbon build kit which reportedly brings the total bike weight down to a much more race-ready and competitive 9.68kg (21.3lb) without pedals which is roughly in keeping with some of the latest and greatest carbon rigs out there. Even so, that complete bike also carries with it a hefty US$7695 price tag and it goes without saying that a lighter frame would bring the weight figure down even further.

Rough and tumble

Racers or climbing specialists looking to shave every last gram will undoubtedly scoff at the Mach 4's weight disadvantage over much of its 100mm-travel competition. However, the extra frame stiffness, vault-like feel and superb suspension that comes along with that extra weight also means that the Mach 4 can be pushed faster and harder through rougher terrain than we would typically expect of bikes in this category and we would also expect it to hold up better in the long run.

As such, riders that don't necessarily place weight at the top of their priority scale who are looking for something a little more substantial than your typical one-season race rig would be well served to pay the Pivot a closer look.

Price: US$1995 (frame, rear shock, press-fit bottom bracket)
Weight: 2.85kg (6.28lb) (medium frame with rear shock, seat collar and derailleur hanger)
Pros: Beefy chassis is stiffer and stouter than most 4" frames, intelligently integrated components, superb dw-link rear suspension
Cons: Frame could stand to lose a few grams, handling may be a bit too quick for some
Cyclingnews rating:
More information: www.pivotcycles.com

Photography

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Images by James Huang/Cyclingnews.com

• The Pivot Cycles Mach 4 is a short-travel cross-country bike that you don't have to baby.
• The key to the Mach 4's performance is its well-executed dw-link rear end.
• A pair of stout links carefully controls the movement of the rear end and keeps rear end flex in check.
• The upper link is carbon fiber and all of the pivot hardware is anodized aluminum. A Fox Racing Shox RP23 ties it all together.
• The press-fit bottom bracket cups allow for a monstrously burly bottom end. Flex? Not a problem here.
• The direct-mount front derailleur tracks the chain as the suspension moves through its travel for better shifts and it also shaves a few grams, too.
• The oversized head tube continues the beefy theme with internal headset cups that allow for a lower bar height if needed.
• The top tube transitions from a square profile up front to a round profile at the seat tube.
• Even the replaceable derailleur hanger is far burlier-looking than we're used to seeing.
• RockShox' superb new SID handled the suspension duties up front.
• We had to flip our PushLoc remote lever upside-down for a better fit with our selected components but the lever was still easy to access on the fly.
• The Specialized Roval Contrôle XC Race Disc wheelset was fast and light though not particularly rigid.
• The straight-pull stainless steel spokes are doubled up on the disc brake side for more even tension.
• The Continental Mountain King 2.4 was a supremely versatile tire that also rolled faster than its appearance would suggest. Best to mount it on a wider rim, though.
• Easton's Monkeylite SL riser bar strikes a near-perfect combination of weight, width, rise and sweep for cross-country applications.
• The Hayes Stroker Carbon features a handy tool-free reach adjust dial.
• As compared to earlier Hayes brakes, the Stroker features larger pads for less heat build-up and more power.
• Don't be fooled by the FSA K-Force Light's carbon construction; it handled rock hits and scrapes with aplomb while also delivering excellent rigidity and shifting performance throughout testing.
• SRAM's X.0 rear derailleur continues to be one of the best gear changers in the industry.
• The SRAM PG-990 11-34T cassette provided the wide-range gearing we were looking for.
• Shimano XTR pedals aren't the lightest around but they're among the most bulletproof and consistent on the market.
• The Easton EA90 stem is quickly shaping up to be one of our favorites thanks to its combination of stiffness and light weight.
• fi'zi:k's new Tundra Carbon saddle is certainly light but make sure its shape suits you as the shell is unyielding rigid and it doesn't break in much.
• The Arundel Dave-O carbon bottle cage is road bike-light but still provides mountain bike-grip.