Hey all - did anyone figure this out? I just got 2 rad runners (single speed) and am trying to fix this too - they BOTH have the exact issue described here.
I'm experiencing this exact same thing with a new Rad Runner. It doesn't even take that much pedal pressure to get it to skip and it happens with or without PAS when pedaling up a modest incline. It's definitely disconcerting and is a possible safety issue as it could cause your foot to slip off of a pedal! There's really very little in the way of adjustments you can make as it's just a chain tensioner and not a derailleur on the Rad Runner. The chainring, tensioner pulleys, and rear single-speed cassette are all in perfect alignment - so, it's not likely to be an alignment issue. I'm wondering if there's a possibility it might be the freehub ratchet that's getting overpowered?
Any additional thoughts on this?
You want some theory. I am good at that and provide one.
Back when I owned a steel bike 15-speed bike, I can put so much force on the pedals that the chain starts to rub on the front derailleur. The chain does not rub the front derailleur when I was pedaling with standard effort. I would say pull up on the right handlebar, pull up on the left foot (in cleats of course), and push down real hard on the right foot. That would move the chainwheel and start the rub. I thought at the time the frame was flexing. With an aluminum ebike, it is hard to imagine the frame flexing.
The solution for me was to pedal faster (work more) but not harder (more torque). My fault was that I was pedaling too hard and not having sufficient cadence. When I start spinning at around 60 rpm all the problems go away. So maybe the solution is to reduce chain tension by using a lower gear and pedaling faster. For me, pushing hard was not the solution for better bicycle performance. Rather, spinning faster was the solution.
I suspect your situation is that everything is in good alignment when there is no tension on the chain but components go out of alignment when you pedal hard.
I suppose you can have a friend look while you push hard on the pedal and squeeze the front brake to see what is flexing. You have to lean the bike against a wall for this test. You can see whether it is the frame, chainring spindle, or maybe even the rear sprocket.