We found a 2mph increase in speed over the 15 mile course. It is a regular course that is ridden by all of us on a weekly basis as a time trial, thus we were all familiar with it. Held on same day for the helmet test and same day for wheel test between three of us, each wearing a different helmet, but using the exact same wheel set and tires. Wind conditions are almost always the same from week to week. It was as controlled a test as we could get. No kidding, the helmet did not help with reducing time over the course. The wheels without question did.