Review on IRC Marbella Tire Tubeless Sidewall by Jeff Kersey

Can you turn your road bike into a gravel bike with a set of IRC Marbella tires? Yes, if you have enough frame clearance (more on that below). Marbellas offer good grip on dirt roads/paths, even if the bottom has a layer of gravel or sand. I can climb loose, rocky singletrack on these tires (which is impossible on my road tires) and they get me over roots pretty well. I haven't tried them on deeper gravel or sand where there is a relatively narrow downside. But when you're converting a road bike, you don't have a choice. These are the widest tires you can fit on most race geometry bikes. Tire Width: In terms of width, you shouldn't have any trouble fitting them on most road bikes. These tires are marked with "28c". When mounted on my rims they were 24.5mm wide, which is only slightly wider than the 25c road tires I normally run. Tire Diameter: Compared to typical 25c street tires, these Marbella 28c gravel tires added 2.25mm to my wheel radius. On a 2006 Allez aluminum frame, the clearance between the tire and the seat tube is less than 2mm. This is probably similar to most race geometry road bikes. Life with a 2mm gap is fine as long as I stay away from sticky dirt.