ΔC is the required reduction in center distance.
L is the belt length.
R is the radius of the larger pulley (driven or driver).
Alternatively, a practical rule of thumb is to reduce the center distance by 1-3% of the total belt length, but this can vary depending on the belt size, tensioning requirements, and pulley configuration.
"Belt Drives and Chain Drives" by Deere & Company
This manual includes design formulas and guidelines for both belt and chain drives, with practical insights into belt tensioning and adjustments.
"Power Transmission Handbook" by the Power Transmission Distributors Association (PTDA)
This handbook is a good reference for understanding power transmission components like belts, pulleys, and chains. It discusses timing belt installation and tensioning in detail.