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 chain stays, that distinctive S-bend of Pinarello’s now-trademark Onda fork blades, and the same machined aluminium 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.
As for the shock itself, it’s quite a simple affair, consisting of two short aluminium 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.
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 realise how much Pinarello had to massage one to produce the other.
While the GAN GR-S may look similar from afar, the chain stays 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.
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 seat-post, 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 fibre 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.
RIDING THE GAN GR-S DISC
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.
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 seat-stays and chain-stays — barely enough to clear the claimed-maximum 38mm tires under the best conditions at all, and well short of established international guidelines.
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.