In part 3 of our series on Wider is Better, we’re going to look at rims. Width is one of the most common places people look to upgrade their stock rims and wheels, but why?
In road bikes, the Zipp Firecrest series were the first major wheels to go wider. Their reasoning was twofold: Aerodynamics and Stability. By going wider, the tire profile did not bulge out as you move from the tire to the rim. For example, the Zipp Firecrest 808 has nearly a flat profile from the spoke bed to the tire bead with a 700x23c tire. This provides a more aero profile over a traditional rim, at any rim depth. By going wider, the stability of the tire is increased by giving it a wider footprint without adding rolling resistance that would come with running a wider tire. Zipp phrases claims the Firecrest “offers greater vertical compliance for control and comfort on rough surfaces while increasing lateral stiffness for sprinting and cornering.” When upgrading an older road bike to wider rims, you may run into interference in the reach chainstays and seatstays, so consult your manufacturer or break out a set of calipers to determine if they’ll fit in your existing bike. Most newer road bikes in the last 2-3 years are designed with these wider rims in mind.
In mountain bikes, wide rims like the Ibis 742 and Stans Flow have become popular over the last few years. Since Mountain bikes do not have rim brakes, there is little to limit you from running rims anywhere from 17mm to 35mm wide on a traditional mountain bike (and up to 100mm wide on a fatbike). The main advantage to going with a wider rim is providing a more square and less rounded tire profile. This puts more of the tire tread on the ground, and less on the sides. Naturally, more tread on the ground will provide more grip (and resistance), but by going too wide you may not have any tread left on the edge to provide grip when the bike is at an angle. By providing a wider base for the tire to be supported, riders often find they are able to run less pressure on a given tire without experiencing the tire rolling over on them due to increased stability.
So is wider better for rims? Generally yes, but remember as width increases so does weight (especially when you’re talking about mountain bike rims at 30mm+), so make sure to pick a rim that fits your application and your frame.