I?m not sure what bolt you are talking about. A 70mm would be like 2 ?? , That?s a really big bolt.
The idler pulley bolt should be tightened to no more than 25 Ft/Lbs and the other bolts that hold the idler pulley bracket should be 20 Ft/Lbs. All these are far less tight you would tend to tighten them if you simply tightened them by feel with a box end wrench. These are not that critical. Just don?t over tighten them.
Hope that helps,
GG
