Veteran helmet brand Giro stepped into the cycling shoe market just a few years ago. The Prolight SLX road shoe leverages the carbon fibre expertise of Giro's sister brand, Easton. True to its name, the Prolight is one of the lighter high-end road kicks on the market. A flat Easton carbon outsole offers a neutral fit and the three offset velcro straps can dial it in, pivoting as necessary on titanium D rings.
In a market crowded with various buckles, ratchets, BOA dials and other types of closures, a three-strap velcro shoe looks a little primitive. But foregoing those buckles sheds weighs, and we found the fit adjustment to be perfectly adequate. In fact, being able to pivot the top strap a bit on the D ring allows for a level of fine tuning that's not possible on a fixed-position ratchet buckle.
The shoes come with a set of Ultralight insoles (11g a piece) and SuperNatural Fit insoles with three different velcro-on arch support options (27g for an insole plus arch support). Both feature silver-fibre X-Static material, which we found to be quite effective in neutralising odour over months of testing.
Claimed weight for a size 42.5 is 205g with an Ultralight liner. Our test size 45 weighs 243g with the included SuperNatural Fit insole with medium arch support. In size 45, we weighed the following single shoes: Sidi Wire, 320g; Shimano R170, 295g; Specialized S-Works, 250g; Bont Zero+, 250g.
The Giro design is philosophically different from the likes of the S-Works and the Zero+ in that the outsole is relatively flat, instead of curving up as part of the arch support. Giro's theory is to leave the shoe neutral and let riders either run it as is, modify the fit with the SuperNatural insole options or use third-party insoles that might not fit in a more-shaped sole. In any event, we found the shoe comfortable, and appreciated being able to play with multiple arch supports without having to pay anything extra.
The Easton sole hits the sweet spot of very stiff and very thin — a claimed 6.5mm — with EC90 SLX carbon fibre. The low stack height brings your foot virtually right on top of the cleat. (Definitely use the short cleat screws for this shoe.) As with all Giro shoes, the three cleat holes are slightly back from where they are on most shoes.
"This was done to help riders using the farther-back cleat placement position," said Simon Fisher, Giro footwear product manager. "We found that 99.9 percent of riders never push a cleat all the way forward, so pushing back a bit did not have any negative effects."
We found this to be true in our case as well, with the cleats centered just a hair behind the ball of the foot, there was still plenty of room for back/forth adjustment.
Each shoe has two heel pads angled to sit level when cleats are mounted. As such, it's a stable, albeit stiff, shoe to walk in.
The upper is a synthetic from Teijin, that held up well over months of testing. When walking, it squeaks a bit, but we didn't notice any noise on the bike. Venting is minimal, but the material is so thin we never experienced overheating.
The heel cup has a relatively taller back portion that drops off steeply for plenty of ankle clearance.
The Giro Prolight SLX comes in white, black and black/yellow. Unlike a few of the other Giro shoes, the Prolight SLX does not come in a wide, or as Giro calls it, 'high volume', option.