The two brushes I've tried so far. I think the big one has real potential. It worked great with the wheel parallel to the brush. It would be easier to use perpendicularly tho so I'll try that tomorrow.
UPDATE: it works better parallel. I think the brush is too soft. Spinning the wheel 3 times still doesn't get it as clean as one time around with the hand brush but with the hand brush I'm moving back and forth while spinning so it actually gives the whole tire 2-3 passes in each direction.
I slid a pipe thru the hand brush to hold it down and used it the same was as the push broom head and it was a little better but not much.
There are dozens and dozens of boot brush/scraper products out there, ranging from $10 to $600+. Some even have water jets. I can't believe there's not a single one for bikes.
If this thing was curved it would be nearly perfect:
Those are rollers between the brushes. It's only $15 so I could buy it and cut out the useful parts to make a custom tire scrubber but it might not be worth the effort.
I'll probably stick with the hand brush for now and if I end up using it a whole lot this winter I'll find a better method for next year.
A "real" bike one would have the rollers aligned in a curve and maybe on springs to fit any tire size. Also, the rollers would be connected to a lever on a riser so you could stand beside the bike and work the lever, spinning the rollers and cleaning the tire. I'd make it mechanical so you don't have to find a place to plug it in.
They didn't worry about that when they designed the Boot Boy. Just pull that lever towards you and it cranks away. It can also apply water and cleaning solutions as it brushes, plus it catches the dirt instead of dumping it on the porch. Only $2,500 and totally useless for bikes. oh well.
![enter image description here](https://cdn.statically.io/img/i.sstatic.net/h9WBZ.jpg)