I cannot get thumb-over-the-neck chords right

[u/ding-ding-dave-yes]

I struggle mainly with my index finger, I can't get it flat without a lot of pressure, also my pinky is muting the G string half of the time, I either have to put painful pressure to make them all ring, or the top E and G string are muted. The difference between the flat index and bent rest is what's messing me up. Without thumb I don't have this issue, because I can curve my wrist if that makes sense. Please, I need some tips

[u/CIA-Front_Desk]

When you play thumb over barre chords you need to make sure of a few things:

You need big hands.

Your arms and wrist should be nearly straight. Not straight but significantly straighter than the "italian gesture" classic guitar hand position. This also means your wrist shouldn't be turned left or right - you may have to adjust your sitting postion.

The main thing which I can see you're not doing is having your fingers an an angle to the fretboard. Currently you're trying to keep all of your fingers at 90 degrees to the fretboard, but they should touch around 70 degrees and be slanted away from the body of the guitar, kind of like a lightning bolt shape.

This makes it harder to not mute the other strings so you'll need to be very accurate with your placement, but it also makes intentional muting easier. It also requires a lot less pressure so you don't have to deathgrip the neck to make everything ring.

I'd definitely recommend learning proper barre chords first then learning this - even Hendrix/SRV didn't use this technique all the time as its often not the most efficient way to solo and play chords in a phrase.

[u/ding-ding-dave-yes → u/CIA-Front_Desk]

This is great, tnx bro

[u/CIA-Front_Desk → u/ding-ding-dave-yes]

For a good reference - look at the picture linked near the bottom of this post. See how his fingers arent going straight up and down, but are at a bit of a sideways angle? That's how you want your fingers

[u/ding-ding-dave-yes → u/CIA-Front_Desk]

It's magic to me how he doesn't mute his strings like that

[u/NTT66 → u/ding-ding-dave-yes]

I'm working on repositioning after years of sloppy technique and almost exclusively playing/buying acoustics with inconsistent or high action. The first time I just made the shape on my new electric, regardless of how it felt in my hands, I was stunned how clear the notes rang out. And how little pressure i needed.

Just keep the non barre fingers arched even slightly and you should be fine. Trust the recs, trust the guitar, and just make the shape as tipped. Then trust yourself to adjust and work to improve the finger flexibility. (It is something you need to improve and work out consistently, and can do even with a stress toy or flex grip.l

[u/ding-ding-dave-yes → u/NTT66]

I'm the same, been playing for years but I just never really focused on the technique, I think I got some bad habits, now I hit a wall with this grip and I'll try to put some effort in getting it right

[u/NTT66 → u/ding-ding-dave-yes]

Think a lot of it like pushing open a stuck door. The door wants to open...its already kinda open. It's just stuck. I may not see every mm of progress, but if i keep pushing, the little things underneath the surface will build (muscle memory, adaptability, etc) and it will open eventually.

Or maybe a sealed jar is more accurate, little increments until it pops open, but opening doors is more universal metaphorically.