Originally Posted by
BlazingPedals
I don't think Vuelta Corsas are particularly great wheels. If you're going to replace your wife's, aim higher. Are you sure the brakes aren't rubbing? I wouldn't expect aero to be a huge factor at 13-15 mph but bearings and brakes might be.
If you really want to speed her up, a
Copenhagen Wheel would do the trick.
They're not particularly great by any stretch but they're awesome compared to what they replaced, especially for the price so I'm a fan. Wheels aren't going to help much objectively anyway, but they do impact our subjective impressions of the ride. Unless the hubs are causing some resistance, which I wouldn't expect on a new bike.
I know we're just making suggestions (per OP's request) but mine based on the limited information is look at the tires and the body position.