Re: What is the largest tire I can get on a WK2 Overland w/ 20" rims and QL? I really
If I am not too late...
The pic has 275/55r20s on it, it is a QL Jeep, not sure which setting it is pictured in. Those tires measure 31.91 x 10.83. The owner indicated no issues (rubbing) when driving in the "normal" setting, not sure about park mode though.
The factory tires measure 30.52" x 10.43" (regardless of 17", 18" or 20" rim). The factory spare is the same OD (30.52") but narrower (9.65"). I think on mine it is a 245/65r18.
Lots of off-road looking tires in a 275/55r20 - Pirelli Scorpions, BFG Rugged Trail, Yokohama Geolander, Nitto's, etc.
You are right, you cannot permanently lift the QL - there are people talking about "kits" to "trick" the airbag system but nothing yet.
Also, you should have as close to the same OD in your spare as possible. Other threads exist that discuss this and it appears that with removing the bins you can fit a 32" OD tire in the spare wheel well. However, the width is where problems arise.