I want to see if anyone has the answer to this question.
Uniform of the US Army, Horse Furniture, published in United Service Journal July, 26 1851 lists spur straps as ¾ inch wide and this is also found in the 1857 US Army Regulations. In the 1861 US Army regulations list them as only 5/8 inch wide.
The army did not change anything without a reason so was there a change in the spurs that caused the reduction in the width of the strap? I have searched for an answer but cannot and I am hoping someone has more information that explains the change.