Can a specially made, foam filled aluminum rim provide a smoother and more forgiving ride? Spank believes that their soon to be released Ooozy 350 Vibrocore rim does exactly that, and it's a technology that they've been using for quite awhile with their Spike 800 Race Vibrocore handlebar.
We've seen rims grow over the last few years to the point that a 30mm internal width, a number that was once unheard of, has become pretty dang normal. But in order for strength to be retained, rim height has also had to increase a good deal, a combination that's made for some stiff and unforgiving rims, especially when they're done in carbon fiber. That's not necessarily a bad thing, of course, but a rim or wheel that's too rigid vertically and laterally can sometimes transfer harsh vibrations right up through the bike and into the rider, especially if large carbon fiber rims are fitted to a short-travel bike. High-volume rubber can help, sure, but there's a reason why World Cup downhillers have been known to run 'soft' wheels that feature lower spoke tension: better tracking and less fatigue. Hell, some of the best racers in the world have been spotted running dual crown forks with arches cut in half, or the same done to their seat stays, in a search for more forgiveness and improved tracking.
Can't a certain amount of flex be built into a carbon rim? Spank believe that they can accomplish the same thing with their foam filled alloy Ooozy 350 Vibrocore rim, and at a much lower price to both the consumer and the environment than anything constructed out of carbon fiber.
The rim itself is an all-new shape for Spank, with an ultra-low height that's designed to allow for a specific amount of vertical compliance, more so than a taller rim that wouldn't flex as much. The corrugated shaped OohBah rim bed is used, as is their Bead Bite anti-burp treatment, but the Vibrocore foam that's hidden inside the rim is the real trick. The low-density green foam is injected into the rim in a soft state, only hardening once inside to expand and provide structural support. Spank's Gavin Vos likened it to a full and unopened can of pop that can support a lot of weight whereas an empty can is easily crushed.
Just like in Spank's Spike 800 Race Vibrocore handlebar, the foam is designed to filter out a lot of that high-frequency buzz that can tire riders out without them even realizing it, but Spank claims that it also allows the low-profile aluminum rim to take in bigger impacts and return to its original shape much more effectively than a standard rim. The Vibrocore rim pictured here is designed with exactly that in mind, and Vos did say that there will be a number of rims designed specifically for the Vibrocore treatment, starting off with a downhill model. I could also see an exceptionally light aluminum cross-country rim using Vibrocore foam to increase strength without adding too much weight; Vos said that the Vibrocore foam adds about 40-grams to a 27.5" rim.
The rim still requires tubeless tape, foam or no foam, and the standard external nipples can be replaced if required as per normal - no special tools or technique required.
Spank plans to have Vibrocore-equipped rims and wheelsets available before the new year, and we'll have a set in for testing quite soon. How much difference will it make? I'm not sure, but I know that the Spike 800 Race Vibrocore handlebar that I tested back in 2014
did surprise me with how effective it was. And, having ridden pretty much every carbon wheelset on the market, I also know that my favorite wheels featured low profile aluminum rims because they simply feel nicer. Either way, Spank's Vibrocore rims sure are interesting.