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Fan Belt Update.


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A few days ago there was a thread on the correct size of the fan belt.  I went with what RealOEM listed.  That proved to not be correct, at least in my '75.


I bought, and tried to install, the listed size of 12.5 x 835.  After fighting to get the existing 10 x 865 belt up over the fan and reversing the procedure with the RealOEM listed belt (for cars with A/C, which mine has) I found out that belt is too short.  I was unable to reinstall the alternator with the 835 length belt around the pulleys.


The 865 belt that was on the car, and is in good shape, was re-installed, tightened up, and all seems to be good.  I'm not sure of the source of the size listed of the shorter belt, but it sure didn't fit in my car.


Just a heads up.  If you need to replace your belt it may be safest to just buy the same size and re-install that one.


Bob Napier

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There are different diameter pulleys for the crankshaft.  The A/C version is larger (turns the fan and water pump faster) for better cooling at low engine speeds.  I have not "looked up" the number for a fan belt in years so it does not surprise me you wound up with the wrong size unless you understood all of the various differences in the different years and equipment.  I doubt even the parts books list everything as most of the A/C was installed at the dealer and there were 3-4 different versions over the years.  If the belt you have fits why would you knowingly  try a different size? 

1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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