I'm wanting to get a front rack for my LHT. It'll mostly be a fashion statement until I can afford to get some bags for it. I'm wondering though, do racks like the Tubus Tara/Ergo interfere with some bicycle racks when you try to lock up? I guess I'm thinking specifically of the "prison bar" format that they have at a few grocery stores around here.

the Hoop over the wheel can be an Issue .. I lock my bike to the side of the rack * or a signpost,
as I occasionally use all 4 panniers to carry the day's shopping home.

* often the wavy-bent tube type . I avoid the low 'wheel bender' racks entirely ..

I am not familiar with this. Do you mean the vertical bars all together in a line? AKA "Wheel bender" racks.

I run front racks and I don't have any problems, but then again, I rarely need to lock my bike. Even if I did feel a compelling need to lock it, I wouldn't use the wheel bender (the interior vertical bars) part of the rack, I would lock to the out side frame of the rack, perpendicular to the rack. With my bike being an Xtracycle, locking the front wheel to the rack is just asking for trouble.

All we have around here are the wave style and the wheel benders.