Shimano RX8 gravel shoe review: Not just mountain bike kicks
Shimano’s new gravel race shoe, the RX8, fills a somewhat unexpected void between its existing shoe options. If you were to draw a Venn diagram with shoes built for cross country and cyclocross racing, and those designed for road racing, the new RX8 would be the circle in the middle — the perfect place for a shoe intended for gravel racing.
And while my first impression was that this shoe was a simplified and re-marketed SPD mountain bike shoe, I’ve since changed that opinion — there’s merit to these shoes for the burgeoning gravel category. Let me explain.
The big story is stability
- What: Shimano’s first gravel race-specific shoe.
- Key features: Longer, harder and flatter pedal interface tread, low weight, stiff sole, secure upper.
- Weight: 595 g (EU43)
- Price: US$249 / AU$380
- Sizes: Men’s (black) 40-50EU, 42-48EU E-width, women’s (Blue) 36-43EU. Silver colourway available in select markets.
- Highs: Road-pedal-like stability from SPD platform, impressively light, secure foothold, clean aesthetics, comfort, price.
- Lows: Walking ability, not a replacement for mountain bike shoes, no reflective details.
Shimano claims that the RX8, its first gravel race shoe, manages to combine the comfort, walkability and practicality of its mountain bike-based SPD system with the reduced weight and improvised pedalling stability of its SPD-SL system.
To do so, the shoes are built on a 10/11 stiffness carbon sole that offers flattened and extended tread blocks surrounding the two-bolt cleats. These tread blocks are optimised for use with Shimano’s latest-gen SPD cross country race pedals (M9100 and M8100), and in turn, do an impressive job at removing the common off-plane rock experienced in SPD pedals.
The uppers are equally road-shoe like too. Shimano has used its supportive “Surround” design which sees one side of the upper wrap over the other, effectively creating a clamshell around your hooves. This material is padded, while the heel cup is noticeably more padded, countersunk, sticky and just generally more secure-feeling than Shimano’s existing top-tier XC9 or even RC9 shoes.
These changes result in a shoe that holds your foot stable with the sole, and the sole stable with the pedal. Swapping between Shimano’s own XC9 race shoes and the RX8s reveals the unexpected – these do in fact feel more like a road shoe. In fact, the fit and feel are extremely reminiscent of the Specialized S-Works Recon, and the similarities are just too close for it to be a coincidence.
And while that stable fit is best with Shimano’s latest SPD pedals, you’ll experience similar improvements on older SPDs too. It’s worth pointing out that Shimano has made these stability changes specifically with its own pedals in mind. Those using SPD-copies will likely see similar benefits but users of new Crankbrothers pedals will already be able to achieve similar results with the pedal’s optional tread blocks.
Fits like a Shimano
Surprisingly the RX8s are a little snugger than Shimano’s own top-tier road and mountain bike race shoes. This is most apparent at the back of the shoe which surrounds the heel more securely than the S-Phyres, while the generally more generous padding also adds to a shoe that fits a touch tighter. And while I suffered from some light pinching issues in Specialized’s Recon shoes, no such discomfort was felt here.
Through this padded heel, the foot is seemingly forced a little more forward and I found the RX8 shoes to feel roughly a quarter size smaller than Shimano’s other race shoes.
Other than that, the fit is exactly what you may have experienced from the likes of Shimano, Giro and Specialized, with a shaping that sits middle of the road to cater to those with near-average feet. I personally have a narrow heel and slightly-below-average-width forefoot and found the regular fit to be comfortable while still offering room to spare at the toebox.
While Shimano typically reserves its adjustable-arch inner soles with velcro-based wedges for its top-tier shoes, they’re included here with the RX8. It’s a feature that adds a premium feel to these race shoes which are effectively a GRX 800-level (Ultegra) shoe.
Each shoe is retained to the foot via a single Boa IP1 dial — that’s looped two-thirds of the way down the shoe — and a velcro strap above the toes. The IP1 dial is a staple in Boa’s premium range and offers dual-direction micro-adjustment and a full release by pulling up on it. Boa themselves provide an almost no-questions-asked lifetime warranty on these dials, and it’s hard to fault the system in function.
The RX8s are available in a rather awesome and stealthy-looking black (tested) or in a blue that’s also a women’s-specific fit. There’s also a wide version available (black only).
walking and spinning
The larger tread blocks that surround the cleat are joined by a somewhat minimalist tread pattern in a hard plastic material that’s resistant to compression under the pedal. Compared to Shimano’s own mountain bike shoes, which typically feature a grippy rubber tread, the material is noticeably hard and is a little slippery when stepping on loose or slick surfaces.
Walk around a bunch and you may be surprised that the hard plastic tread isn’t so hard-wearing. While the tread blocks on my samples are still fine and functional, they show wear that isn’t present on my mountain bike shoes with even more usage. I suspect this wear is directly related to the tread sliding on surfaces rather than gripping firmly.
Add in the snug hold, stiff sole and no provisions for toe studs and these shoes are clearly not made for extended efforts on foot or for sprinting up grass embankments. However they do keep the cleats enclosed, and so remain a huge improvement over road and road-style touring shoes, too.
With less tread and no toe spikes, Shimano has whittled away the weight. My EU43 test sample weighed 595 g, which is 95 g lighter than the more expensive S-Phyre XC9 and, impressively, still 15 g lighter than the Specialized S-Works Recon.
That weight is more impressive when you consider the shoes offer some toe protection from rock strikes, a rubber toe bumper to keep the front of the shoes in good knick, and a treaded area behind the cleat in case you miss the pedal or are wanting to scoot along unclipped.
Up top the one-piece synthetic leather upper is generously perforated, however the combination of the Surround Wrap upper design (which overlaps the two sides of the upper) and no sole-based ventilation like a road shoe, these shoes do a decent, albeit not great job of keeping sweat at bay. That minimal ventilation is fine for most conditions, but slow grinding rides on a hot summer’s day will leave your feet feeling a little clammy.
I still wanted MTB shoes for MTBing
Proving that the RX8 shoes are not simply a lightened mountain bike shoe, I actually missed my cross country race shoes when riding trails. The pure stability and snug hold offered by the RX8s somewhat limit you from using a little body English to maneuver a bike in technical trail sections, and instead, I could feel the loads coming through my knees, shins and ankles in an effort to let the bike dance. It’s the same complaint I had of the Specialized S-Works Recons when comparing them to the Shimano S-Phyre XC9s, and while it’s totally a personal issue, it’s worth noting that more foot security isn’t always better.
In this sense, if you ride gravel, road and mountain bikes, then the RX8s may not be the silver bullet you hope them to be. I still prefer the absolute stability, low stack height and improved cornering clearance of a dedicated road pedal system when on the tarmac. Similarly, I prefer the easier walking, stickier tread and more forgiving fit of a mountain bike shoe when riding trails. And if you’re looking to do a bunch of walking, then an even more flexible and grippy shoe, such as Shimano’s own XC5, is certainly worth a shout.
However, Shimano nailed the brief with its RX8s when it comes to pedalling over mixed surfaces as efficiently as possible (with SPD-type pedals). These truly do offer the gravel race crowd a positive point of difference, and they’re a seriously good option to consider against the likes of the more expensive and similarly secure Specialized S-Works Recon and Giro Empire VR90.