Yeah, I had a bit of a similar suprise a few days ago when I installed my winter wheels as well. Did the job last year and everything was fine. I use different bolts for my winter wheels. I recently had warranty suspension work done on the Jeep, a few days before I swapped the wheels here at home. The two wheels that had been taken off for the suspension work were overtightened, my electric impact gun got most of them off but I had to use a breaker bar for a few of them. Two of them stayed stuck inside the 19mm socket (with impact gun). I was able to get one out by putting it back in with the wheel still on the hub, gave it a few impact jolts, reloosen and out of the socket it came. The second one I screwed back a few turns into the hub directly (no wheel), and just yanked on the deep socket until it popped out (I got lucky). Then I looked at the bolt heads that got stuck, thinking the tech had used the wrong socket (too big) and damaged them. Well, he damaged them alright, but not with a wrong sized socket ; he got only half the head and gunned it down, overthightening it at the same time, so I could see the damaged metal in the middle of the head, which is where my deep socket gripped. So now I have two damaged bolts and I'm not sure if I can salvage them. I think (as I write this) I'm gonna pay them a visit and ask for two new bolts... so stay tuned...
Now about the size . They are metric : M12x1.25 with a 28mm shank (27mm will do too), and with a conical seat.
For my winter wheels I got black tuner bolts from Amazon. Tuner bolts have smaller heads for wheels that have small lug holes, and they come with their own special socket. The ones I got are of course M12x1.25 with a 28mm shank and conical seat, they just have a smaller head which is fine. The wheels I bought didn't require tuner bolts but those were the only black bolts I could get on Amazon (I'm in Canada so a slightly different Amazon than the one in the US). These tuner bolts are not high quality : I could tell as soon as I got them off in the spring, they had a bit of corrrosion/rust at the tip. But I don't mind, I got them fairly cheap.
These are my tuner bolts (Amazon US) : https://www.amazon.com/CECO-Spline-I...rds=B00WFBZ3KO
These are some Otis zinc coated ones (dunno if they are any good) : https://www.amazon.com/Otis-Inc-Euro...rds=B005MMQFJ6
The OEM Cherokee bolts are likely made by McGuard : http://www.mcgard.com/index.php/auto...gory_pathway=0
(those have a shank length of a little less than 26mm so I'm not sure... They must have a fitment chart somewhere...)
Link to Otis site for maybe more info (same bolts as the ones on Amazon I think) : http://www.otisincla.com/index.php?r...roduct_id=1206
($40 for a box of 20 ain't bad...)
Edit to add, Just found some nice Gorilla chrome tuner bolts that may be of higher quality : https://www.amazon.com/Gorilla-Autom...Q9ZWHM4X4QY27Y
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2015 North (Canada) - V6 - AD1
Cold, Tow, 8.4A, 9 speakers with sub