The Specialized Rhombus Pro is a brand new option from Specialized set to do battle in the competitive best gravel bike tire space. It comes fitted as standard on the brand's progressive geometry flat-bar Diverge Evo bikes. It comes as no surprise then that it’s a proper ripper on the trail but a buoyant ride quality and easy road speed are a real bonus for a bombproof tire.
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The Rhombus' 575g weight is definitely on the hefty side, even for a 42mm tire, but it uses a 60tpi version of Specialized’s well-proven Endurant edge-to-edge protected carcass. It’s 2Bliss too and inflation onto our default DT test wheels was instant, even with a low-volume track pump. They locked in place evenly at 30psi rather than needing over-pressuring. Their 42mm labeled size actually measures 43.5mm on a 25mm internal rim, and the 575g claimed weight is bang on as the actual weight too.
The center tread is a tight pack of siped knobs in a varying arrowhead design with a gap across to much bigger intermediate and shoulder knobs that extend to the full width of the carcass. The rubber compound is Specialized’s proprietary Gripton recipe.
As you might expect, the big, wide-spaced knobs do a great job of biting into sloppy, slippery or loose conditions, whether you’re braking, driving, cornering or clawing control out of an off-camber. That meant test rides soon became a ‘can we ride that’ challenge that the Rhombus Pro consistently won. Even in full-winter flood conditions, across off-camber CX style grass banks or throwing it super hard into wet, wooded singletrack corners, the Rhombus railed and nailed everything, letting us ride our rigid, drop barred gravel bike host almost as hard as an XC MTB. Despite the reinforcement, the Endurant carcass feels very smooth and compliant, adding to both the root/rock molding control and comfort. While you can feel the weight when accelerating, they’ve got a lovely buoyant life to them once you’ve got them up to speed, and the overall ride feel is one of the best we’ve experienced from any brand.
Most surprising was how well they rolled on the road. There’s a bit of high-pitched buzz but very little obvious drag, and we had no problem keeping pace with file tread tires. The open, relatively tall knob intermediate/shoulder tread needs treating more gingerly in corners, but when it does slide, it’s predictable and saveable. The fact the knobs go right to the overhang also means it’s a consistent drift - on-road or off - rather than a sudden let go if you lean too far.
While we’ve not been on the Rhombus Pro for long, we’ve rimmed them several times without worry and long-term experience with Endurant and Gripton suggests they’ll be tough and long-lasting, too. The only real downside is that there’s no different width or 650B options.
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Verdict
The Specialized Rhombus Pro tires match decent straight-line speed with almost mountain-bike-level cornering and tech-line traction. A fully protected carcass adds weight but they still ride really smoothly, and the tubeless setup is 2Blissfully simple. Add a bargain price, and the Gravel category has a new benchmark to be measured against - as long as you only want 700x42mm.
Tech Specs: Specialized Rhombus Pro gravel tires
- Price: $60 / £45
- Weight: 575g
- Sizes: 700 x 42mm
- Colors: Black
