First Time Spare Ribs...wondering where I went wrong

Try cutting into St Louis style. Hard to say. I just go by dome but I wrap mine. They'll be 900 different opinions on how to cook ribs. Try different methods till YOU find your sweet spot. I go 325 for a little over a hour, wrap for close to a hour then 30 minutes sauced. That's the way I like them. They tug off the bone. A little longer in each step makes them feel odd the bone. If the family enjoyed the meal... It's a win.

My comment and just like an opinion "we all have one"-you can get too wrapped around temperature especially if you have more than one thermo working the cook.  I find it best to go with one that is calibrated (key word)  (dome is the one all BGE's have).   I know what the dome means relative to approximate cook times (since we all cook to temp); the thermo/temp is only a guide to what's happening and that's close enough.  FWIW-YMMV-

 

I usually do spares at ~300°F, raised indirect, no wrapping or spritzing,  and they are done in about 3 hours. Almost a hot n fast cook but not quite. I go by the dome thermo.

I suspect you may be being to hard on yourself. But I think its better for the cook to disappoint oneself and still please the eaters. Means the cook may keep improving.

Here's how I judge my own.

Poorly cooked is "mushy" fall off the bone. The meat protein has been so denatured that there is no structure left. Besides the mouthfeel, the bones still appear sort of wet, and small bit of meat still cling to them. This happens to me more often if I foil, so I don't anymore.

What I always hope for, but is still elusive, is when the bones fall out of the meat. The bones look dry and white. The meat still has a fiber structure, but is otherwise so tender that it can be shredded with fingers. The trick seems to be catching the meat when a bend test almost causes the rack to fall in two.

Undercooked always seems dry and tough, tho' one can seem the moisture on the inside meat. I have over cooked a few times when racks were lighter weight. The meat mostly becomes brittle and dessicated.

I usually do a quick peak at the ribs at what I think should be the 3/4 time mark. If there is not good meat draw back from the bone at that time, I know I will need longer. If the meat surface seems to be getting dull and dry, I will give it a very light brush of plain water.

As already mentioned, the difference between the dome and the grill level usually is different, but it is usually the dome that is hotter. At the start, anyway. I have used an IR therm to measure the temp of the platesetter when the dome is at 250. I measured temps close to 500F. Perhaps the probe was picking some of that up.