That pic is really old. I had it the "regular" way for awhile. Then we discussed putting it the way I have it in that pic (under the idler pulley) since that seemed to make more sense. It allowed the smooth part of the belt to contact the smooth pulley. I have since changed it back since some folks were telling me that having it go under the pulley would cause abnormal tension on it.

I don't think a consensus was ever arrived at and to be honest, I don't think it made any difference either way.

Both ways worked fine.

 

Doc,
I called ATI yesterday and asked which way they reccommend. The tech advised that either way was OK. He then said that it should be installed as per the manual. I asked about belt wear due to the teeth on the pulley and he said that was not an issue. The belt wear and failures are from heat and improper tensioning of the belt. So, I guess it really doesn't matter as long as the belt is adjusted properly.