Am reviving a 2002 R53 with a (PO stated) reduced pulley and wondering what the correct serpentine belt length shoudl be.

I seem to get some slipping/squealing at higher RPMs/torque

The PO work is questionable so having him mention that he put a reduced pulley on, I'm not sure if he adjusted belt length accordingly so I'd like to get the right belt on.

I don't know what pulley is on the car.

 

Discovered it is a Alta 15% so this belt chart is applicable

https://altaperformance.com/i-156921...reduction.html

 

If its a 15% SCP, then use a NAPA # 25-060535 - They are usually in stock.....Effective Length is 53.54"