What size is your rear hub? I squeezed a 130mm rear hub into an old steel frame and it pushed the driveside chainstay out a little more than the non drive side due to the factory bend (for the chain ring clearance on that side). It always crabbed but when I starightened my bars it wanted to go right, however doing no hands it always favoured going left. I#d say just check your stays and see if they're both equally straight with the string method.
What size is your rear hub? I squeezed a 130mm rear hub into an old steel frame and it pushed the driveside chainstay out a little more than the non drive side due to the factory bend (for the chain ring clearance on that side). It always crabbed but when I starightened my bars it wanted to go right, however doing no hands it always favoured going left. I#d say just check your stays and see if they're both equally straight with the string method.