I bought a serp belt 9186352 from Tasca maybe 3 years ago and it was longer than the original 1995 take off(i never discard old parts). I double checked the tasca web site then and that was the only belt shown so I put it out of my mind. I checked that old belt and finally got a number off it 9146557, and it's seems to still be available. I put 9146557 in tasca and it comes back with a serp belt and it says it fits my 95 volvo. There is also a hyperlink there for 'belts and pulleys' and when i click on that i get a diagram with more parts but this diagram lists the proper belt as 9186352. Now the longer belt gets a different routing so it can wrap around the alternator pulley more and get a better grip. Implied is the longer belt and new routing is the way to go and fortunately I think the idler and alt still turn the same direction. Anybody have the scoop? The belt on the car I haven't taken off yet, the dealer put it on in 2005. It has what is considered the short belt routing. Here is Robert with some more info. What OEM belt is in your VOlVO? Did you change the routing? I bet using the longer belt with the short routing would not work.
https://www.youtube.com/watch?v=vyoNw8B6QWM