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by James Huang
March 10, 2017
Photography by James Huang
Pinarello entered the red-hot gravel bike market earlier this year with two entries: the GAN GR Disc plus and the decidedly more progressive GAN GR-S Disc model, which uses the same rear elastomeric mini-shock as on the Dogma K8-S. All the gravel bike requirements are checked on the GAN GR-S Disc, including disc brakes, thru-axles, relaxed handling, and clearance for tires up to 38mm-wide. But is that enough to compete in what is rapidly becoming a highly contested market? US technical editor James Huang isn’t so sure.
The GAN GR-S Disc shares strong family ties to the Dogma K8-S, with similarly shaped front triangles and tube profiles, the same “Flexstay” flattened chainstays, that distinctive S-bend of Pinarello’s now-trademark Onda fork blades, and the same machined aluminum rear shock. Just as on the Dogma K8-S, Pinarello says there’s up to 10mm of rear wheel travel on tap for a smoother ride and better traction, all without adversely affecting frame stiffness or drivetrain efficiency.
The Pinarello GAN GR-S Disc bears a strong family resemblance to the more road-oriented Dogma K8-S. Photo: Pinarello.
As for the shock itself, it’s quite a simple affair, consisting of two short aluminum tubes that telescope inside one another, a short chunk of microcellular urethane foam, a stainless steel shaft, a single-lip wiper seal, and a few composite bushings to help keep everything linear. There’s also a simple threaded preload collar to adjust the amount of force required to get everything moving.
All told, it’s basically a tiny version of what many mountain-bike suspension forks looked like two decades ago — hardly groundbreaking in terms of technology, although in fairness to Pinarello, there’s less required in this application, too.
The GAN GR-S Disc’s defining feature is this little elastomeric shock. The 10mm of claimed maximum rear travel is likely only to come when hitting something really, really hard.
Alas, for as many similarities as there are between the Dogma K8-S and GAN GR-S Disc, the former is hardly suited for gravel with its modest tire clearance, and it’s only when you inspect the respective geometry charts that you realize how much Pinarello had to massage one to produce the other.
While the GAN GR-S may look similar from afar, the chainstays are 10mm longer, the head tube angle is slightly slacker, and there’s more rake on the fork, all of which add about 20mm to the wheelbase, depending on size, for more stability on loose terrain. Reach is similar across the board, but stack is increased a substantial 20mm or so on the GAN GR-S for a more upright and relaxed position. Interestingly, though, Pinarello actually raises the bottom bracket on the GAN GR-S by 5mm relative to the Dogma K8-S — the exact opposite of what’s typical in the gravel scene.
While the Dogma K8-S and GAN GR-S Disc share many traits, they differ substantially in terms of geometry. Photo: Pinarello.
Geometry aside, there are the more obvious changes to suit the GAN GR-S to modern gravel riding: the stays and fork blades are more widely spaced for higher-volume tires — up to 38mm, according to Pinarello — flat-mount disc brakes are fitted at both ends, and the wheels are held in place by 12mm thru-axles. Fender mounts are included, too, along with a tidy hidden binder for the proprietary carbon seatpost, dual bottle mounts, internal cable routing, and — hallelujah — a traditional Italian threaded bottom bracket.
Pinarello doesn’t quote a claimed weight for the GAN GR-S frame, but given the inflated dimensions and more run-of-the-mill carbon fiber blend (a move ostensibly made to boost the GAN GR-S Disc’s impact resistance for gravel riding), it’s fair to assume that it’d be a bit heavier than the 990g official figure for the Dogma K8-S.
The chainstays are radically flattened, but also very wide.
Pinarello offers the GAN GR-S Disc in two complete builds. This particular sample features the higher-end Shimano Ultegra kit, complete with appropriately wide-range gearing (52/36T chainrings, 11-32T cassette), mechanical Shimano RS685 shift/brake levers, and matching RS805 flat-mount hydraulic disc brake calipers with 160mm-diameter rotors. Rolling stock consists of Fulcrum Racing 5 DB aluminum clinchers wrapped with 35mm-wide Vittoria Adventure tires. Pinarello’s MOst house brand provides a flared aluminum handlebar and forged aluminum stem, and it’s all topped with a fi’zi:k Antares k:ium saddle.
Total weight for a 50cm sample is 9.26kg (20.41lb), without pedals.
With higher-volume tires inflated to just 40psi and the added benefit of rear suspension, it’s little surprise that the GAN GR-S Disc rides quite smoothly on rough ground. As always, the tires do most of the heavy lifting in terms of evening out the ground, but the rear suspension does come into play here, particularly on bigger bumps; I regularly finished test rides with visible evidence that the rear shock had moved several millimeters.
Nevertheless, the rear shock stealthily goes about its business, with little tangible evidence that it’s moving aside from the fact that your rear end is jolted slightly less than usual. There’s little evidence through the pedals that anything is amiss, either, as the rear end feels like any other medium-stiff bike with no obvious squishiness when you put down the power.
Pinarello has done a good job of keeping the rear end from wagging around under power, despite the fact that it’s designed to move quite a bit when hitting bumps. The shock integration is admirably discreet and tidy.
Front triangle torsional stiffness is good, too, with a sturdy feel when sprinting out of the saddle or torquing the handlebars through a tricky section of trail.
However, just like on other predominantly rear-suspended road bikes — like the Trek Domane, for example — there’s a certain imbalance to how the front and rear ends even out the ground. While the clever rear shock on the GAN GR-S Disc does an impressive job of evening out especially jarring surfaces like badly washboarded dirt roads, there’s no mechanical device to assist your arms and hands. It’s not enough to be overly disruptive in most situations, mind you, but it’s hard not to notice the disparate ride qualities of either end when things get really bumpy.
The fork features Pinarello’s trademark curvature. Even so, there’s a marked difference in how the front and rear ends behave over bumps.
Handling traits of the GAN GR-S Disc are as expected. The long wheelbase and slack angles provide lots of stability for confidently traveling slippery gravel roads, and you’re more likely to drift safely through loose corners instead of abruptly swapping ends. If your idea of a good day in the saddle is spending long hours casually cruising the less-traveled backroads, the GAN GR-S Disc’s calm demeanor will suit the task nicely.
Further adding to the bike’s versatile confidence are the wide-range transmission — a 36-32T low gear is enough to climb the steepest walls, while a generous 52-11T top-end ratio is plenty for the fastest descents — and Shimano’s superb hydraulic disc brakes. Stopping power is more than ample, yet the fine control means you only lock up a wheel when you want to — all with a light and fluid lever feel to boot.
The flat-mount front and rear Shimano disc brakes both feature 160mm-diameter rotors.
While that easygoing stability is one of the defining traits of a true gravel bike (as compared to the somewhat more nervous nature of more dedicated cyclocross racers), with the GAN GR-S Disc, Pinarello has missed the mark in a few key areas.
Perhaps most critically, Pinarello has overstated the GAN GR-S Disc’s tire clearance. Up front, there’s only 46mm of space in between the fork blades, while the rear end is even further pinched with barely 40mm of room separating the left and right seatstays and chainstays — barely enough to clear the claimed-maximum 38mm tires under the best conditions at all, and well short of established international guidelines.
Pinarello seems to have overstated the GAN GR-S Disc’s tire clearance as there is barely 40mm of space in between the seatstays and chainstays — not nearly enough to safely accommodate the claimed 38mm maximum allowable tire width.
Likewise, while the rear suspension unit does work, it falls short of the claimed maximum travel. On full-suspension mountain bike frames, actual wheel travel is usually some multiple of shock stroke since the leverage ratio — how much the wheel moves vs. how much the shock compresses — is rarely 1-to-1. On the GAN GR-S Disc, however, the rear shock is almost collinear with the rear wheel’s direction of travel, and the total shock stroke is just 6mm. Even with no preload on the threaded collar, I rarely saw any more than 5mm of movement.
Further diminishing the GAN GR-S Disc’s capabilities and fun factor are multiple missteps in terms of spec.
The wheel-and-tire package is unduly heavy and cumbersome, and that excessive rotating mass dominates the ride experience. Each of those Vittoria Adventure tires is nearly 600g — aided in no small part by low-budget steel beads — and the inner tubes add another 130g apiece. Moreover, claimed weight on the Fulcrum Racing 5 DB wheels is a reasonable 1,710g, but the actual weight is a hair shy of 1,800g.
The tread design on the stock Vittoria Adventure tires provides decent grip on both asphalt and dirt, but the thick casing rolls slowly and stiffens the ride quality. Both tires also measured significantly narrower than labeled.
Granted, the thick casings that come with the Adventure tires’ weight are just what you want for more extreme gravel surfaces, but few GAN GR-S Disc buyers will regularly tackle the flint hills of Kansas. On the more tame dirt and gravel roads this bike is apt to see, the tires feel stiff and dead. But worst of all, they’re not even as wide as the labels describe; both measured barely 32mm across, even at 50psi. Swapping to a set of true-to-size 36mm-wide Clement X’Plor MSO tubeless clinchers, with their more supple 120TPI casings, did wonders for both ride quality and speed.
Opinions will vary on the flared aluminum drop handlebar, but Pinarello’s choice of tape seems misdirected at best. The wrap is paper-thin and provides no cushioning for your hands, and the surface is slippery even with good gloves. Similarly, the fi’z:k Antares saddle is smartly shaped, but it’s hard to stay planted on rough roads with the slick cover.
The Pinarello GAN GR-S Disc seems like a good gravel racer on paper, but its limited tire clearance means it’ll probably be best suited to the Pinarello-faithful who are looking to stray just slightly off the beaten path.
The head tube shaping is rather awkward without a conventional rim brake caliper to fill in the gap at the crown.
The main tubes are nominally aero, although it’s unlikely most people buying a bike like this will place much weight on how efficiently the structure slices through the wind.
The top tube shaping likely adds little in terms of function, but it does add some style.
The internal cable routing is mostly neat and tidy in terms of appearances, but the actual cable paths and angles could use some refinement.
The stock Formula thru-axles tighten securely, but are clunky to operate as compared to more refined options from SRAM, DT Swiss, Fox, and others.
In a cycling world increasingly dominated by press-fit shells, the use of easier-to-service (and quieter) threaded bottom bracket cups is most welcome.
Fender mounts are included all around, but there isn’t much space left around the stays or fork crown for them to fit.
Clearance up front is slightly more generous with 46mm of space in between the fork blades – but still not enough for the high-volume rubber many true gravel riders will want to use.
The hourglass-profile head tube houses a tapered 1 1/8-to-1 1/2″ carbon fiber steerer tube. Note the hose rub on the front of the head tube, just above the fork crown.
The seatpost binder is neatly hidden away inside the top tube.
The Shimano Ultegra crank is a smart choice as it’s reasonably light, shifts supremely well, and has a proven reliability record.
The R685 brake/shift levers aren’t the prettiest in the Shimano catalog, but they fit nicely in your hands and work well.
Not everyone will like the look of a mid-length derailleur cage, but it’s a small aesthetic price to pay for the more useful gearing range.
52/36T chainrings pair with the 11-32T cassette for a wide gearing range that doesn’t sacrifice the top end.
The Fulcrum Racing 5 DB wheels used here are almost 100g heavier than claimed, and their 17mm internal rim width isn’t a great match for the wide-profile tires this bike will typically see in day-to-day use.
Fulcrum’s choice to stick with its trademark 2-to-1 spoke lacing pattern on a disc-equipped rear wheel can be debated.
Pinarello has long championed the benefits of its highly asymmetrical frame designs – including top tubes and down tubes. Whether there’s much real-world benefit, though, is not as clear.
The flared handlebar will invariably be a love-it-or-hate-it item.
The bar tape, however, seems like a poor choice regardless of preferences. It provides no cushioning whatsoever on rough terrain, and the surface is woefully slippery.
The pseudo-aero theme carries through to the MOst stem (with its wedge-type steerer clamp) and profiled headset spacers.
Is the GAN GR-S Disc truly a gravel bike, or is Pinarello just trying to capitalize on an emerging trend?
The fi’zi:k Antares saddle is comfortable, but the cover is quite slippery.