Too hard to tell without repeated sprints and recorded data on both. But I gained 3 mph on my max speed with my new shoes. I struggled to hit 45 with my old shoes but hit 48 with the new white shoes, same jersey and helmet.
You need some of these!
IMG_3094 by
mrbeanz1, on Flickr
Oh I forgot, I was riding new GP4000s as well. You need some of these too!
GP4000 by
gulpxtreme, on Flickr