The fan belt that is turned by the crank pulley....a converted a/c pulley....turning the GM alternator is screaming and throwing rubber dust. I am thinking that it may be too thin.....

How do you measure or calculate the correct thickness on a belt?

what was the thickness of the AC belt that used to ride in that pulley ? that's where i'd start... if you have metric on one end and American on the other end -- i donno, except you may be looking at compromises. but perhaps all belts are metric - been so long since i've had to buy any other kind i just donno...

when i did the mix-n-match thing in the GTI i just measured the opening in the pulley at the point i wanted the belt to ride - approximately as deep as the original belt - and it turned out to be 17mm (IIR) which was a standard size so i figure i guessed right. i used a tape measure (which was about as wide as the Belt In Question) and wrapped it around the pulleys where the belt was supposed to and got an approximation of length - i had quite a bit of travel in the adjuster...

too thick, and the belt won't ride deep enough in the pulley and will get flung out. too thin and it will pinch at the bottom - as well as not driving stuff fast enough... but there are not -that- many standard sizes so it shouldn't be too hard to find something 'close enough' ...

Thanks....bought one slightly smaller and one size thicker....

The old one was screaming and coming apart.

Geez....thicker belt and 1/4 inch smaller in diameter and now it's 3 inches on adjustment. Small changes on the belt size make BIG changes on the pulley.....