rubber drive roller or steel?

I don't have enough experience with friction drive to help you masterx. When I first built the Jdog I made it a friction drive and used a fence post as a drive wheel. Worked okay just did not like the friction drive so I swapped it over to chain.

I would think the rubber drive wheel would work better but I guess the steel one would last longer. But with out having much time on a friction drive and never using a rubber drive wheel I just don't know. Be patient I am sure others with more experience will jump in.

Well here is my humble opinion thought it is antidotal not real side by side comparison. I have used metal friction drive wheels and found them adequate but also found them to be rough as heck on tires. small rubber wheel like a skateboard seem to do well. I think they actually have more grip but thats just me. My weight runs between 200 and 220 lbs these days.

I now use a 12" scooter rear wheel on my ebike friction drive and find it perfect. It is best not to run knobby tires on a small wheel friction drive, it will beat the motor and drive to death. Constant and deep vibrations you see. On the drive I use, it makes no difference for some reason. I guess that is because the wheel is large enough to roll right over the indentations. No vibrations. Of course it does look weird. That's why I call it a rhino drive. It looks like one giant horn on the bike either front or back.

Good luck and I love friction drive best. If I were going back to gas and I do threaten to every few weeks, I would go with gas friction drive on the rear wheel.

When I built mine I did a lot of reading on this forum. It seems that by and large the steel is the best all around. I have about 375 miles on mine and it appears that the tire will last in excess of 1000 miles. I have very little slippage. I use a heavy spring for tension and and have a small turnbuckle for fine tuning.
Elmo