Shimano S-Phyre RC903 PWR review: a great improvement on an already very good shoe

Named among our North American Editor's favourite products of 2024, the Shimano S-Phyre RC903 PWR builds upon the standard RC903 platform, refining the design specifically to aid higher power riders and efforts such as track racers, sprinters, and time triallists. Let's see how they stack up compared to the original model.

Construction

The sole is the same semi-covered carbon used on the original model, with Shimano's higher stiffness rating of 12. Most of the sole is not visible from the outside as it is wrapped by the same material as the upper. Cleats are attached via a 3-bolt system that has fore and aft adjustment, as well as a mapping system to ensure accurate cleat placement.

The same heel cup is also used, which features what Shimano calls 'anti-twist stabilization' to maintain optimal foot position and prevent any twisting. It also features a fairly narrow heel point to provide additional security.

This heel counter and the underside hard coating now feature a colour-shifting finish, a feature not available on the standard RC903 shoes. Shimano also utilises the same insole with adjustable arch support, providing a more tailored fit.

Another new feature is the use of a separate tongue, which features multiple perforations designed to improve breathability. Multiple holes across the upper and vents in the sole are designed to further assist with this.

The PWR uses the same Boa Li2 dials for adjustment, but has reduced this to one metal dial; on the RC903, this was only an option available to professional riders, such as Mathieu van der Poel.

This single dial features seven turn points to create a powerful compound pulley system designed to allow for increased levels of retention and force application. A Velcro strap is also used for retention on the forefoot, allowing for the use of track straps, which a lower dial would not permit.

The shoes are available in sizes from 36-48 with half sizes from 39.5-46.5, plus the same range of wide fit options. The white colourway is presently the only one available. Our size 45 wide fit came out at 546g for a pair.

The ride

First and foremost, these are shoes that are designed to grip your feet and not let go. This does make the initial process of putting them on a slight faff admittedly.

The now no longer tongueless design means that slipping the shoes on can fold the tongue down into the shoe. This is made all the more likely by the fact that, with just a single dial to open the shoes, and one that has so many pivot points, the opening is difficult to widen and requires some manipulation of the wires.

Once these shoes are on, however, they are impressive. The single Boa Li2 dial might seem like a downgrade from the two-dialled version of the RC903 shoes. However, with seven turn points along the retention wire, this results in a mightily effective compound pulley system.

What this essentially means, with a bit of help from Archimedes, is that more force can be applied across the retention system with smaller tightening increments. This allows for an incredibly tight maximum retention that is significantly better than any other shoe I've tested.

The closest competitor is the S-Works Ares shoe, which uses four turn points on the upper dial. I also appreciate the new metal Boa dial, which looks more premium. With its textured finish, it is easy to grip and provides massive retention.

Being a Li2 dial, micro-adjustments are possible in both directions, with a 'pull to release' mechanism making the shoes easier to take off than get on.

Adding to this overall retention is the same heel cup as used in the standard RC903 shoes. This is rigid to provide anti-rotation so when really putting down the power there is no twisting around the ankles. These shoes also have a narrower top around the ankle, which suits me well to allow zero heel slip when pulling up on the pedals during sprints.

The Velcro strap is another interesting addition, as personally I never really adjusted it. However, it has been added in lieu of a second dial for track sprinters. A Boa dial does not allow for the use of toe straps easily, while a Velcro strap accommodates this. For 2500+ watt sprint efforts, this is a vital addition, although maybe superfluous for most road cyclists, and especially myself. It takes nothing away from the shoes though.

The final piece of this monster power transfer platform is the carbon fibre sole. This is the same sole as the standard RC903 shoes and has a stiffness rating of 12, the stiffest Shimano offers. However, in conjunction with the upper retention system, the overall system stiffness is far greater than any other shoe that I’ve used. The likes of Nimbl do appear to have a stiffer carbon sole when comparing the Ultimate platform with the standard RC903, but the enhanced retention capacities of the RC903 PWR make for a total system that feels significantly stiffer and more planted. For maximal efforts and out of the saddle attacks, the RC903 PWR are truly unmatched.

It's not all about power though. The increased level of adjustment for the retention makes for an impressively comfortable shoe; I would say more so than the standard RC903. Aiding this is the perforated tongue and increased breathability of the shoes, making them more pleasant in warmer environments.

The same arch adjustable sole is also used, which is nicely supportive and stiff. Another great addition is the broad size range with half sizes and all sizes available across the wide fit model. A single colour option is a tad limiting, but the white with iridescent accents look superb to me.

At 546g, these are 30g heavier than the standard RC903 shoes, but that weight is not noticeable. Only ultra featherweights like the Nimbl Ultimate Air feel noticeably lighter when pedalling at a higher cadence, but even then at higher power outputs the increased system stiffness outweighs the perception of lightweight. For a race day shoe, these are truly exceptional.

Value & conclusion

At £349.99 / $525, these are an expensive pair of cycling shoes, but they pack a lot of high-tech features into them. They are the same price as the standard RC903 shoes, and offer better value to me as a race day shoe with the enhanced retention. They also undercut the likes of Specialized with the S-Works Torch (from £350/ $449), Sidi Shot 2S (from £425/ $524), Nimble Ultimate Air (from £425 / $549), and DMT KR0 EVO (from £350/ $409).

There are cheaper options, the Specialized Torch lace starts at £219/ $349, but using laces means zero on-the-fly adjustment, while the Canyon Tempr CFR is £319.95/ $329.95 and a touch lighter. The Canyon is likely the most similar shoe in design and features, but the sock-like upper is tough to clean, and the heel is a little more roomy, making for a lower system stiffness.

There is also an element of how you aim to use the shoes. If you are a sprinter or track racer, there is likely nothing else off-the-shelf that will rival the RC903 PWR shoes. If you are a more relaxed type of rider, not as focused on peak power efforts, then there are lower specification shoes that may suit your needs better. If weight is the sole focus, again there are more suitable options. I think for maximal power transfer, and the psychological feeling that every ounce of effort is transferring to forward momentum, then the Shimano RC903 PWR shoes are an exceptional piece of kit and justify the higher price.

The Shimano S-Phyre RC903 PWR shoes have been designed specifically for high-power efforts like time trials, sprints, and track races. To that end, they deliver exceptional performance and have probably the highest system stiffness I’ve ever experienced. A very clever retention system, secure yet comfortable fit, and improved breathability, all for the same price as the standard RC903, make these a no-brainer if you're choosing between the two models. They are not the most featherweight, but the stiffness makes a more noticeable impact on performance than the additional few grams. Add to that the great adjustment allowing them to be comfortable enough for long, easier rides, and these are a superb pair of shoes that I struggle to find any real fault with.