Carmarthen-born Davies, 20, won the British Under-23 time trial title in 2014 and 2015.
Harrison, 23, won bronze and silver in the team pursuit at the UCI Track Cycling World Championships in 2011 and 2013 respectively.
They join fellow Welshman Owain Doull at Team Wiggins, which was launched in January 2015.
Welsh cyclists Scott Davies and Sam Harrison have joined Sir Bradley Wiggins' Team Wiggins.