Several other rugby players joined the challenge, including Martin Johnson, Alix Popham, Dean Ryan, Carl Hogg, Mike Teague, Colin Charvis and Iwan Tukalo.
The group is aiming to raise £250,000 for research into treatments for motor neurone disease (MND).
On arrival to the Principality Stadium in Cardiff, Mr Wainwright told the BBC: "The support we had on the way down was unbelievable.”
He sung Weir’s praises and added: “He’s such an inspiration to us and to everyone”.
This is the third year riders have completed the Doddie Cup 500. In 2020, those who took part got an average of three hours of sleep across the 48-hour-long ride, which saw them maintain speeds of 15mph to deliver the match ball on time.
Weir was unable to make the Scotland versus Wales match as planned, as he recently tested positive for Covid.
Wales emerged triumphant 20-17 over Scotland as players competed for the Doddie Weir cup, named after the former Scotland international lock in 2018.
Donations can be made on the Doddie Cup 500 fundraising page.