chaadster

Given that the critical rim specs are very similar between the alu GX and carbon fiber GXX, and that the wheels are otherwise the same, I wouldn’t expect any substantial difference between them.

The GXX does have an aero profile whereas the GX is a box profile, so that might account for some drag reduction, but they’re both quite shallow, in the 24mm range, so not at all the typical aero height, and the thick PBO spokes and long, proprietary nipples probably render meaningless any talk of “aero advantages.”

The GX aluminum is 1/4lb lighter, but also 1mm narrower at 24mm IW, both of which are probably undetectable at the pedals and bars.

I’ve only been riding GX for 1.5 years, but they’ve been excellent and perfect gravel wheels for me. I run either 35s or 42mm rubber, and both feel sporty and responsive on the wheels, so more roadie than MTB, if you know what mean. They’re stiff and can get knocked around and still feel like they’re going forward, so no problems there. When I want to snap, they jump, so climbing and sprinting are good, too. And though decidedly non-aero, perhaps because of my large size and heft, the few watts penalty they cost easily gets lost in the big numbers I need to put out to keep my hulking mass clipping along decently. I mean, I’m strong and fast enough to be in the top 25% at events and races, but were I in podium contention, I don’t think I’d run Spinergy at all because of their un-aero quality. The big deal is in the smoothness and comfort of the wheels, which is noticeably better than conventional spoked wheels; they really take the edge off dirt roads, softening the buzz. I do think a little wind-up is part and parcel of that comfort, and it may take a sec to get used to, but as a diesel accustomed to using momentum, that little springiness made immediate sense to me, and so as I said, I find them excellent.