I'm getting ready to do some maint. (Oil Service) and will replace the A/C belt tensioner while I'm in the engine bay, as it's stuffed. Looking up the BMW part number gives me 64557786706. Searching this part gives me a number of different options - some are the full tensioner pulley inc. the pivot arm and others are just a pulley wheel and bearing.
I would replace just the internal bearing if I thought I could get it out of the pulley wheel without breaking the pulley wheel, but I guess it's a cheap enough part to replace at least the whole pulley and bearing. I *think* the pulley wheel is 65mm x 21mm but some options seem to be 70mm x 26mm.
If you have replaced yours, what did you use? Do you have either the measurements or the old part to measure up? I have the under-shield back on the car right now and so cannot measure my own one - I will remove it all again if I have to but I though it worth asking here first!
TIA...