Usually friction drives use too much pressure on the tire at all times or a roller that has too much friction enhancements to it which chew up the tire. I'm hoping to avoid both.
The motor right now has a bike tube wrapped around it and even without it is perfectly smooth and would slip if it tried to apply too much pressure. I know of two others using similar progressive pressure designs that I based mine on and they have not had any issues yet of excess tire wear but from their miles don't ride near as much as I used to and hope to again.
Actually except for one schwalbe marathon plus tire I had on my fuji xtracycle I can't recall ever having a tire wear out before it was destroyed by other means
Time will tell though.
The drive fully comes off the bike in about a minute turning it back into a regular bike. I'm using it only as a power assist unit only to get me back into my commute and level out a few of the tougher hills that my HR shoots up uncomfortably if I ride it solo. It should also help with a few tough sections which I have to sprint to survive otherwise the drive will never touch the tire. All which should minimize tire impact and maximize my time out getting some exercise.
There are many options out there but after reviewing them all against what I needed this seemed not only the best match overall but the cheapest too. Cheaper still if you take into account I"m using the lithium batteries I got for my lawnmower to power it and the controller and motor I could put in my remote control truck to run it. It's practically free