Review of the Shimano S-Phyre RC-903 Shoes

For the fourth iteration of its high-end S-Phyre shoes (following the RC-9 released in 2017, the RC-901 in 2019, and the RC-902 in 2021), Shimano appears to have definitively resolved the usual trade-off between performance and comfort in the new RC-903, thanks to an upper and lacing system that provide a secure fit without creating any pressure points. These shoes are just as popular with pros as they are with amateurs and long-distance riders.

By Guillaume Judas – Photos: @3Bikes.fr

The S-Phyre RC-903 retains the features that made the first models so successful, namely a very stiff outsole directly connected to the upper and its snug fit, an insole with adjustable arch support, a slight arch, and a slim heel with an anti-twist shell to limit unwanted foot movement while pedalling. On this new model—already being used by pros like Mathieu van der Poel as of the 2022 season—Shimano has primarily reworked the interweaving of the microfiber leather layers in the upper, resulting in an even softer and more progressive fit than on previous models. This same upper also feels slightly more supple to us (without being stretchy when tightened) than the previous RC-902 version, and significantly less stiff than the 2019 RC-901 model.

Shoes that truly stand out from the competition

One of the S-Phyre’s key features is its construction method, which omits the midsole typically used to secure the upper between the (carbon) outsole and the comfort insole. The upper is attached directly beneath the carbon sole, which allows both sides of the shoe to gradually close around the foot at the same time when laced up, and gains a few millimeters of height between the foot and the outsole, theoretically providing additional stability for the foot on the pedal.

The S-Phyre also features a very stiff sole (a rating of 12/12 on the Shimano scale), It features a fairly flat arch and a relatively wide cleat area, allowing for a wide range of adjustment with less risk of overhang when placing the cleats—a process further facilitated by numerous markings. If you’re switching to this model from another pair of shoes, you’ll likely need to lower your saddle by a few millimeters to get back into the swing of things.

The S-Phyre also features an insole with adjustable arch support, offering a choice between two thicknesses of cushions (included with the shoes), which provides good support for the midfoot and ensures even pressure distribution throughout the shoe. Note, however, that we would have liked an additional thickness option for greater support when needed. In fact, the “high” support level (red) is roughly equivalent to the blue insole sold separately by Specialized (the “medium” option), and in our opinion, an additional level is needed for those with very high arches. Nevertheless, the brand’s effort to provide customizable arch support is already commendable compared to other brands. The S-Phyre RC-903 retains the two Boa Li2 dials for tightening, which are slim and allow for step-by-step tightening and loosening. At the instep, the dial sits on the shoe’s main flap, unlike most shoes on the market. This theoretically improves the fit around the foot, as the two Boa closures pull the cords in opposite directions. The Boa Li2 systems are precise and powerful, though not as much as the Boa S3 systems found on Specialized shoes, for example. However, they allow you to completely release the tension with a single pull, which is not the case with the S3 systems.

One of the main differences from the first three generations of S-Phyre is the Boa lacing system on the forefoot, which now runs directly through the fabric rather than following plastic guides. This makes the shoe lighter, reduces the risk of pressure points when tightening, and distributes pressure more evenly. Unlike the RC-902, there is a mesh section at the front, designed to improve layering as the shoe wraps around the foot and tightens. Shimano stiffened the rear of the shoe, particularly around the instep and heel, while using more flexible and elastic materials and a design in the forefoot to optimise comfort. The heel is particularly slim and snugly wraps around the entire back of the foot, preventing the foot from lifting or slipping while pedaling. Ventilation in the S-Phyre RC-903 is provided by the thin, perforated microfiber leather on the upper and by an air intake beneath the front portion of the carbon sole. Small ventilation holes are also visible on the insoles, at the front and back.

Finally, in terms of weight, the RC-903s are lighter, weighing in at 218 g each in size 39, compared to 230 g for the RC-902s—a savings of 24 g per pair.

The S-Phyre RC-903 is available in four colours (white, black, blue, and red), and in sizes 36 through 48 (with half sizes from 37 to 47, in a wide fit—with an additional 3 to 4 mm of width in the forefoot—and in a narrower women’s fit from size 36 to 44 (available only in white). The finish is superb and fully justifies the high-end retail price of €349, though it is slightly lower than many competing models, which now hover around €400 or even €450. Also worth noting is a replaceable heel pad and a rubber protective plate at the front of the sole, designed to minimize damage in the event of friction with the front tire.

S-Phyre RC-903: comfort and performance The fit is comparable to the RC-902 version, with a fairly narrow entry that provides excellent heel support, but with a forefoot area where the toes have enough room to spread out comfortably without overlapping. When tightening, the instep area is always quite surprising, as the Boa cord’s placement—which is offset from the usual position—eliminates that “strap” sensation that you might normally rely on for support when pushing down on the pedals. Here, the support is even across the entire foot, with no hard spots, and you rely solely on the shoe’s progressive fit around the foot to feel completely at one with the entire bike. From our perspective, adjusting both Boa dials is essential for proper tightening.

The very flexible upper material allows for a lot of freedom in the forefoot if the shoe isn’t laced properly. On the other hand, a tight fit is perfectly comfortable over long periods thanks to the shoe’s design. It remains to be seen, however, how this softened microfiber leather will age over time, and whether it can continue to provide the same level of support and fit after being exposed to numerous harsh weather conditions—something we were unable to verify after 1,200 km of testing.

The carbon sole is very stiff, but again it must be paired with proper overall tightening, as it alone is not enough to ensure optimal performance if the foot isn’t sufficiently secured at the upper. But once the shoe is properly laced—with the sole and heel securely fastened and the upper wrapped tightly around the foot—it literally presses the foot against the shoe, delivering top-level performance.

We also appreciate the low arch of the sole, which allows for a very natural motion while pedaling. And most importantly, when using Shimano cleats, we’ve found that the cleats stay perfectly aligned without any warping when tightened, whereas with some other shoes, they can warp slightly, resulting in play when making contact with the pedal.

Our review of the Shimano S-Phyre RC-903 shoes

Lightweight and comfortable, the S-Phyre RC-903 offers a minimalist fit that feels like wearing slippers, but can become noticeably stiffer when tightened firmly, allowing the foot to truly become one with the shoe. The outsole delivers solid stability and a natural pedal stroke that doesn’t hinder ankle movement. The insole, meanwhile, offers custom support options that aren’t all that common even at this price point. And while this is subjective, we think they look great. It remains to be seen how the microfiber leather and the mesh portion of the upper will age, both aesthetically and in terms of functionality.

The SHIMANO S-PHYRE RC-902 at a glance…

Rating: *****

Pros: comfort, build quality, snug fit, stiffness, low arch height Cons: exposed, thin, flexible upper; mesh section that gets dirty easily

Soles: carbon (stiffness rating 12/12) – Upper: microfiber leather and mesh with no midsole – Heel: wraparound – Closure: two independent Boa Li2 closures for micro-adjustment – Perforations for drainage or ventilation – Insoles: with adjustable arch support – Cleat adjustment range: 11 mm – Weight: 218 g (size 39) – Colors: black, blue, white, red – Sizes: 36–48 with half sizes, available in classic, wide, or women’s (narrower) fits – Price: €349.99