Problems with high tollerance filament (under 1.70)

Hi everyone, unfortunately Im having some problems using an abs (not zortax filament) that dont have good tolerances (the diameter drops below 1.70 reaching sometimes 1.65), on other machines I have no problems, but on zortrax M200 (as you know have a fixed filament traction) my prints stop because the m200 are unable to pull the filament … has anyone try to find a solution for this problem? Maybe putting a circular shim on the bearing? By doing so i think the extruder gear can “squeeze” the filament with more force … (Considering that the extruder gear cant be modified). I’d like to have your opinion …

I think exists small assembly tolerances for extruder motor screws. You can try to loose motor screws a little then push the motor to bearing side in same time tighten the screws, maybe this can help a little.