Taking place overnight from 7pm to 7am on 23 June they hope to raise £2,000 for the Bristol Down Syndrome Trust and Cancer Research UK.
Tim Davies said: “This is the seventh charity ride that we have taken part in and we are determined to try and match the sum raised last year.
“Previous rides have included trips along the river Danube from Bratislava to Budapest, through Holland and Belgium and a gruelling ride across Northern Ireland so it’s nice to do something much closer to home.
“The path that surrounds Queen Square will certainly prove interesting testing the endurance not only of the riders but also the bikes.
“We’re all trying to train as much as possible but more importantly trying to get as much sponsorship as we can from our friends and colleagues!”
To donate please go to http://www.charitygiving.co.uk/