Wiggle's customer offered to trade his MG Rover ZR for new Mekk 2G Poggio Ultegra road bike.
Thomas Dibley, Wiggle's cycle marketing manager, said:
"I was in the office when this tweet came in. Our mutual reaction was 'let's do it', so as soon as we figured out who would actually take ownership of this car, we accepted the offer."
Dibley added: "I'm pretty sure we at Wiggle won't be trading too many more cars for bikes."
However, customers quickly started to make other trade-in offers, including spouses.
@spokemasher tweeted: "How about swapping my wife for two wheels please, eh? No photo until after the trade though."