Coinciding exercise with peak serum caffeine does not improve cycling performance.

Skinner TL, Jenkins DG, Taaffe DR, Leveritt MD, Coombes JS.

Source

The University of Queensland, School of Human Movement Studies, Australia.

 J Sci Med Sport. 2012 May 31. [Epub ahead of print]

Bottom line, to boost your performance by as much as 2%, drink your coffee (caffeine) one hour prior to your endurance event.