Extruder idler tension  

When adjusting filament extruder tension, there's no way to know in forward if tension is appropriate or not -it's all about feeling and common sense (depending on filament and extruder type/construction).
I usually start with lower tension (just enough for gears to grab the filament). I check that, by loading few centimeters of filament and then try to pull it back. If I can pull out filament easily, then I increase tension a bit. Indicator of too big tension can be too deep gear traces on filament at extruder output -some traces are always visible, though.
Before I start with actual print, I always check with extruder calibration. Needless to say, that extruder calibration must be done on heated hotend (proper temp. for particular filament), so filament actually melts trough nozzle (as in actual print). I say that, because I saw some video(s), where extruder calibration was done without filament going into print head -no need to explain what that's wrong.
If I get correct calibration result (without some "strange" noise from extruder) then it's time for small test print.

Others might have different/better approach.

I just go by feel (on non-Prusa extruder)

It really depends on your extruder. I've got one of the clone extruders on my Sidewinder and it's pure guesswork. I just eject the filament and give it a look now and then. If it's gouged up, I back the tension out a bit.

Idler tension

Posted by: @bobstro

It really depends on your extruder. I've got one of the clone extruders on my Sidewinder and it's pure guesswork. I just eject the filament and give it a look now and then. If it's gouged up, I back the tension out a bit.

The same is true with one Bondtech I have and a few fo the Chinese clones.  

How much is enough

@cwbullet and @bobstrow  I kindda thought thats what you'd say. Can I infer from your remarks that you'd be looking for minimum pressure consistant reliable filament feed. Anybody know what would be the consiquence of too much pressure? 

grind

For me, too much pressure leads to clicking and grinding of filament.  

Thanks

Thanks

"Improve your prints" video

Step 3 shows how to calibrate the tension correctly.

thanks for the vid

@lichtjaeger.

Thanks for the video. So we're going for minimum pressure.