Pedalling/peddling

Tour de France is the longest and the most scenic cycle race in the world. Along the way, hard-peddling cyclists pass through fashionable cities, peaceful countryside, fruitful vineyards and along breezy coastlines.

Peddling is the way the feet work to make the bicycle move. When the passage you gave describes the cyclists here as "hard-peddling", it means in effect that they are moving very fast or "peddling hard". This would make sense since the Tour de France is race.

From Merriam-Webster online:

Main Entry: 3ped·al
Pronunciation: 'pe-d&l
Function: verb
Inflected Form(s): ped·aled also ped·alled; ped·al·ing also ped·al·ling /'pe-d&l-i[ng], 'ped-li[ng]/
Date: 1888
intransitive senses
1 : to ride a bicycle
2 : to use or work a pedal

Main Entry: ped·dle
Pronunciation: 'pe-d&l
Function: verb
Inflected Form(s): ped·dled; ped·dling /'ped-li[ng], 'pe-d&l-i[ng]/
Etymology: back-formation from peddler, from Middle English pedlere
Date: 1532
intransitive senses
1 : to travel about with wares for sale; broadly : SELL
2 : to be busy with trifles : PIDDLE
transitive senses
1 : to sell or offer for sale from place to place : HAWK; broadly : SELL
2 : to deal out or seek to disseminate