So... I fancy myself a strong time trialist and am looking for advice on bang for the buck in aero wheels. I use a wheelbuilder aero jacket cover on my rear (powertap) wheel. I am about to get a 40 mm front wheel (set actually) to use for training and racing. In TTs I've used a 27mm 18 spoke Easton ea90 rim (mine), and borrowed Zipp 404, Zipp 1080, HED jet 90... My 2 best 10 mile TTs were on the Easton, my best 40 km on the HED. All at about 27-27.7 mph. My intuition tells me I will be faster with the 40mm front and quasi disc rear than the 27mm... But I wonder if anyone has any idea how many seconds could be gained over a 40mm rim to say a 60mm, a HED3, or HED 3D, or 85-90mm wheel?