Belt Tension???

[masbury]

Installing new belts, tensioners and pulley's, but not sure of procedure for belt tension. Is it a deflection dimension, or tensioner length, or some really bizarre method?
Thanks ahead

[Sniff38]

I did this exact job about 4 months ago and was wondering the same thing. My research led me to the "90 degree twist" rule-of-thumb. Using your fingers, twist the belt in the middle of the longest span . . . you're looking for 90 degrees of twist. If you can't twist it 90 degrees, the belt's too tight. If you can twist it more than 90 degrees, it's too loose. I did a little back and forth with the tensioner until I got it right, but so far this method hasn't let me down (no slippage or squeaks). I wish I had something more scientific to offer. Perhaps someone else will chime in.

Sean

[Timm]

They have a fixed tension as set by the spring dampeners - although for the M62 this explains the process:

http://www.meeknet.co.uk/E38/M62_Alternator_Belt.pdf

[shogun]

E32 M70 workshop manual has the details
https://www.bmwtechinfo.com/repair/m...es/4810080.jpg

[masbury]

Forgot to mention '91 850 with M70.

Thank you gentlemen

[8Tech]

Tensioners are automatic, sprung and damped. I compress the damper until it is about half way compressed then lock up the adjuster. The spring tension in the damper will apply the correct tension and the internal damper stops any vibration.