Pivot Vault gravel bike first-ride review: Elegantly simple, buttery smooth

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Bike companies have been coming out with all sorts of mechanical devices to improve rider comfort on gravel bikes: Cannondale recently introduced Kingpin on its new Topstone Carbon, Specialized incorporated the Future Shock into its Diverge, Trek has IsoSpeed on the Checkpoint, there’s the radical full-suspension Niner MCR, and so on.

Pivot has instead gone a far simpler route with its revamped Vault, using an elastomer sleeve called Iso Flex. It may not be the prettiest thing, but Iso Flex does serve to remind us that keeping it simple often works just as well as the more complex stuff.

Story Highlights

  • What it is: The latest iteration of Pivot’s dedicated gravel bike.
  • Frame features: Carbon fiber construction with Hollow Core Internal Molding Technology, Iso Flex elastomeric seatpost insert, dual bottle mounts, front and rear fender mounts, internal cable routing, BB386EVO press-fit bottom bracket shell.
  • Claimed maximum tire size: 700x45mm, 650x51mm
  • Weight: 998g (claimed, frame only, medium size, painted, without Iso Flex insert); 8.18kg (18.04lb, actual, medium complete Force-equipped bike without pedals)
  • Price: US$6,700 / AU$10,000 / £6,400 / €8,050 (with SRAM Force eTap AXS); US$5,200 / AU$8,000 / £5,000 / €6,250 (with Shimano Ultegra mechanical); US$2,700 / AU$4,250 / £2,800 / €3,250 (frameset only).

Deceptively simple, impressively effective

It wasn’t long ago that suspension travel wasn’t part of the discussion when it came to gravel bikes. Those higher-volume tires were originally thought to provide all the suspension most riders needed, but yet an increasing number of bike brands are going for even bigger gains, and ever-cushier ride qualities, as the boundaries for what these bikes can and should be doing continue to be pushed.

The latest entry in the field, the Cannondale Topstone, boasts up to 30mm of movement at the saddle on rough terrain, courtesy of a single-pivot pseudo-suspension design called Kingpin — almost the same amount that softail mountain bikes were bragging about a couple of decades ago.

Rather than chase lots of wheel movement, however, Pivot has instead decided to concentrate more on vibration absorption with Iso Flex, with a few millimeters of physical movement as a nice bonus.

The defining feature of the new Pivot Vault gravel bike is its Iso Flex shock damping system.

As it turns out, Iso Flex isn’t even really part of the Vault frame itself. Tucked into the somewhat awkward-looking seat cluster of the Vault’s carbon fiber frame, Iso Flex comprises a co-molded plastic-and-elastomer sleeve that sits in between the seatpost and the frame. The elastomer serves the same function as the engine mounts in your car, attenuating harsh vibrations from the road that would otherwise be transmitted straight up into the saddle, while also providing a modest amount of suspension to further isolate the rider from harsh impacts.

Iso Flex is offered in several different variants.

The seatpost is isolated from the frame by a high-density elastomer sleeve that provides a surprising amount of isolation from vibration and bump impacts.

For maximum comfort, Pivot recommends running a 27.2mm-diameter seatpost and the thicker-walled Iso Flex insert, which not only provides more inherent seatpost flex on bumps, but also the most suspension movement and vibration isolation since there’s more elastomer in between you and the rest of the frame. Another option pairs a more thin-walled insert with a 30.9mm-diameter seatpost, and is aimed at rowdier-minded gravel riders that want to run a dropper post, but still want some measure of vibration isolation.

Just one Iso Flex insert hardness will be available at launch, but other stiffnesses are likely to follow later so that riders have more tuning choices.

Straying further into gravel territory

Iso Flex may be the defining feature of the new Vault, but even without it, there’s a lot to take in.

Pivot’s first-generation Vault was a bit of a jack-of-all-trades-master-of-none machine when it debuted in 2013. Ostensibly billed initially as a cyclocross bike, Pivot hedged its bets by including compatibility for both rim and disc brakes, swappable dropout inserts for 130mm and 135mm quick-release rear wheels, and a toned-down geometry that was neither traditional CX-quick nor particularly stable.

Subsequent updates moved the Vault further into the gravel realm, and this latest version is now fully immersed in the scene. Sure, you can still use the new Vault to race cyclocross, but that’s clearly less of an intent than it ever was.

Pivot says that tires up to 700x45mm or 650x51mm will fit just fine. 700x40mm-wide Maxxis Ramblers come stock on complete builds.

Tire clearance has improved dramatically, with room now for 700c tires up to 45mm in width (an increase of 9mm), or 650b ones up to 51mm across — and if anything, those figures seem a bit conservative.

Frame geometry also remains on the more stable end of the spectrum, but with a few tweaks that should nevertheless make this latest iteration feel a tad sportier than its predecessor, without sacrificing stability at high speeds or on loose terrain.

Head tube angles are mostly unchanged, but chainstay lengths have shrunk to 420mm (a decrease of 5mm) despite the improved tire clearance. Bottom brackets have dropped by 5mm as well, while wheelbases lengthen by a handful of millimeters on most sizes. Speaking of sizes, tall rides will be happy to hear that Pivot has finally added an extra-large variant, bringing the total range of sizes of five, supposedly covering riders from 1.5m (5ft) to 1.96m (6ft 5in) in height.

Details, details, details

Given that Iso Flex takes care of the lion’s share of rider comfort, Pivot placed a greater priority on weight and stiffness elsewhere on the Vault. According to Pivot, compliance hasn’t been ignored completely — even without Iso Flex, the new Vault is said to be more comfortable than before — but frame designers now supposedly didn’t have to make as many compromises to provide that cushy ride. Notably, Pivot says bottom bracket stiffness has increased, too.

Claimed frame weight is a respectable 998g for a medium size. That includes paint, but not the Iso Flex insert itself (which supposedly adds 56g).

Visually, the most dramatic feature on the new Vault is the dual dropped chainstays, which, combined with the wide-format BB386EVO press-fit bottom bracket (a format that Pivot founder Chris Cocalis pioneered back in 2011) allow for that impressive tire clearance while still leaving room for two-chainring cranksets.

The chainstay shape will be visually jarring to some, but it’s where an increasing number of gravel bikes are going these days. Common problems, common solutions.

Also included are front and rear fender mounts, internal cable routing for mechanical or electronic drivetrains, mounts for a top tube feed bag, a large hatch under the bottom bracket for easier servicing and hidden Shimano Di2 battery storage, 12mm front and rear thru-axles, flat-mount front and rear disc brake interfaces, and optional covers for the routing ports and removable front derailleur mount depending on drivetrain choices.

As has quickly become the norm, Pivot provides two mounting positions for the down tube bottle, which can be very handy, particularly for riders that like to run frame bags. Notably missing, however, is a third bottle mount beneath the down tube or accessory mounts on the fork blades. Gravel bikes are quickly segmenting into ones made for speed and ones made for versatility and capability, and it’s clear in which camp the Vault falls.

Multiple holes on the down tube allow for some flexibility in bottle cage positioning, but two bottles is still all you get here.

Pivot will offer the Vault in two complete builds for now, one with SRAM Force eTap AXS and 23mm-wide Reynolds ATR-X carbon wheels for US$6,700 / AU$10,000 / £6,400 / €8,050, and the other with Shimano Ultegra mechanical and DT Swiss CR 1600 aluminum clinchers for US$5,200 / AU$8,000 / £5,000 / €6,250. There’s also a frameset-only option for US$2,700 / AU$4,250 / £2,800 / €3,250, and dropper posts will be available as stock equipment for an additional charge on those complete builds, too.

Actual complete weight for a medium Force-equipped build is 8.18kg (18.04lb), without pedals, and with a fixed seatpost.

Sampling the Vault

I didn’t have a chance to ride the new Vault during the launch event in Fruita, Colorado (where Pivot also debuted the new Mach 4 SL cross-country race bike), but the company actually did one better by stopping by CyclingTips’ US office in Boulder, CO with a sample. That ride wasn’t terribly long, but the mix of tarmac, gravel, and rocky singletrack still provided enough time to get a good first impression of the Iso Flex system.

In short, it not only works as advertised, it’s better than I expected.

Complete bikes with two-chainring drivetrains will come with Praxis cranksets, fitted with sub-compact 48/32T chainrings. Smart.

Iso Flex doesn’t provide heaps of movement like Trek’s IsoSpeed system or the Kingpin micro-suspension design on Cannondale’s new Topstone Carbon. But it nevertheless is remarkably adept at squelching unpleasant vibrations from the road or trail, while also providing more movement than I’d anticipated, given the description.

It’s not suspension exactly, and that effect obviously goes away if you stand up. That said, Iso Flex still makes for a very notably smooth and muted feel out back, almost as if you’re running several psi less in your back tire than usual, but without a hint of bounciness. Keep in mind, too, that my loaner was also fitted with a dropper seatpost, so if anything, the ride quality with a 27.2mm post will likely be even better.

Interestingly, the bike I rode was a test mule that was also equipped with a Redshift ShockStop suspension stem — a bit that I reviewed in the past at length, and still greatly admire. In that configuration, I found the Vault to offer an impressively balanced and planted ride front-to-rear, to the point where I wonder if the Vault would feel harsh up front with a standard stem. Unfortunately, Pivot doesn’t offer the Redshift stem as a stock option, but it sure seems like a shame not to.

The seatstays aren’t particularly small, but then again, with the Iso Flex system, they don’t have to be. Instead, most of the frame can be tuned more for stiffness and efficiency.

Ride quality aside, the Vault’s stiff backbone feels admirably responsive under power, and the handling is spot-on for the segment: stable to the point of inspiring confidence on slippery ground, but not so much so that it feels sluggish and resistant to handlebar inputs.

Overall, it was certainly an entertaining ride, and an eye-opening one as well. We expect a production sample for a proper long-term test shortly, so stay tuned for a more in-depth report in the weeks and months ahead.


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