Because you have installed the 2 buttons and associated pin,, which type you have is obvious..
Those buttons/block don't butt the carrier,, there is space for them to float betwen the 2 axles,, so tightening up one axle, transmits thru the buttons/block to push the other axle against it bearings..
But.. if you didn't install the pin properly and peen the end over to capture the 2 buttons,, often 1 button will fall out,, and cause a "no adjustment" situation,, check both buttons are there..
hope it helps..
