Some non-foiler input here (I'm sure foiling is fine, I'm just too lazy to do it plus I like how my ribs come out without foiling) - just cook 'em until they pass the bend test (you pick up one end with tongs, forming an approximately 90 degree angle, or pick up from the middle and the ribs hang down both sides - the exterior starts to crack) confirm with a toothpick - it'll slide right in and out, or see if you can grab a bone and twist it kinda easily. That's basically it for knowing when they're done.
Make that some additional non-foiler input.
50" Klose BYC, Spitjack XB85, 22.5 WSM, Backwoods Chubby, UDS, WRK, 26" & 22.5" Weber Kettles, Jumbo Joe, WGA, WSJ/MUDS, Jumbo Old Smokey, a piece of expanded metal I throw over the fire pit sometimes, Stealthy Black & Vol Orange
Displaced East Tennesseean
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Former outlaw MOINK baller, now IMBAS Certified, but still lookin' over my shoulder.
"Relax, it's only BBQ.
" - Bigmista, 2013
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