Narrower is not necessarily faster as noted by JDT. A tire with supple casing, smooth tread, and at the proper pressure is the key. Too-high pressure results in increased suspension losses (vibrations transmitted to the rider). For every combination of tire and rider, there is an optimum pressure that combines lowered hysteresis losses (casing and tread flexing) and lowered suspension losses. For tires in the 28 mm width range, that pressure is around 6-7 bar (80-90 psi). For wider tires (with similar casing and tread) the optimum pressure declines. Bicycle Quarterly has done extensive research on this and explains it well: https://www.renehersecycles.com/tire...re-calculator/