What is this loud "thump/ pop?"

[sb001]

So after my bug has sat for a few hours, and I go to drive it, I put in any gear (reverse, Drive 1 etc) and hit the gas, it doesn't move initially (like the e-brake is still on) and then if I press the gas more, there is a sudden "POP" that sounds like it comes from the right rear side of the car and it releases, and it feels like that side of the car actually rises up as the car begins to move and then comes back down, like it's rolling over something only on that side. Only does it that one initial time and then it's fine.
But, after driving a bit and everything warmed up, if I park it for a bit (like going to the store) and then get in to drive it again, it does not do it.
Only after the car has been parked for a few hours or more, and then it does it again every single time.
My first thought was rear brake shoes rusted to drums, but they can't re-rust themselves to the drums in that short a period of time. Something to do with the rear torsion bar perhaps??
Any suggestions appreciated
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1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[nogoodwithusernames]

Check your brake adjustment. Also try parking with no e-brake and just put some blocks under the wheels and see if it happens. Maybe crusty e-brake cable not releasing well?
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71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[BMFBMF]

I'm guessing oval drums, as you ride. They warm up quite quickly and might not cause trouble but as soon as they cool down they could start catching again.
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-----Slava Ukraini-----
1971 Stock South African Beetle 1300 : My mom's european "Thin Chick" spec. Completely stock with torsion bar front, swingaxle rear, smooth hubs, single MC, 40 mm shoes, 31PICT3 carb and 5 bolt drums all round, currently Running a 1976 SF:AS engine with the original SF:AD engine overhauled in a box, waiting to go back in one day.

[bsairhead]

Could also be a rusty gland nut bearing.

[vamram]

Corrosion in the right rear cylinder that "rebinds" after a few hours...?
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[jeffrey8164]

Definitely a puzzle. If you park it in the garage I would park it. Jack it up, take off the wheel wait for it to cool down and see if you can turn the wheel by hand. See if you can hear where the popping comes from. You may have to pull the drum to see what’s going on.
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[a8ked]

It might be a sticking EBrake lever inside the drum. A small dab of brake grease on the EBrake lever pivot pin might solve the problem. I've seen some very rusty ones that would hang up when the brake cable was released.

[scrivyscriv]

You’re describing a stuck brake.
Suspect the wheel cylinder and/or flex hose.
Additionally, if the drums and shoes are heavily worn, the cylinder pistons may be overtravelling and getting cocked in the bore.
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[Eric&Barb]

[sb001]

Thanks for the suggestions
Eric & Barb this was my original thought I just thought there is no way it can re-rust to the drum in that short period of time, but maybe so.
Scrivvy I do also agree it is most likely brake related, and I thought about the wheel cylinder. At first chance I will try to get the drum off to have a look.
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[volksworld]

there may be brake fluid that has leaked onto the shoe making it stick to the drum when parked