According to the developer, they have spent a lot of time trying out different materials for the roller, and the urethane they ended up using will last as long as the motor and also minimizes tire wear. They minimize the need for extreme grip by having a system that adjusts the amount of pressure on the tire and increases the pressure only when needed as in when it is raining, which also allows it to work well in wet weather.
There are other friction drives out there that use a kind of sandpaper covering for the roller! Sandpaper! It of course causes a lot of tire wear and also the covering itself wears out quickly and needs to be replaced. This unit's roller is not like that.
The position of the weight is possibly less of an issue since the entire system including battery and motor weighs between 4.5 and 7.25 pounds when it is installed. That is much less than most other electric drive systems, and less than some of the available front wheel motors by themselves before you include the weight of the battery. I ordered a version with a mid-sized battery that weighs about 5.5 pounds, and I figure if I want more range, I could pick up a spare battery to carry elsewhere on the bike. But even the system with the largest battery is only about 7.25 pounds total weight. There are front racks for panniers that weigh 3 pounds just for the rack itself! And some handlebar bags weigh a pound and a half just for the bag. This unit mounts half way between the position of a set of panniers and a handlebar bag, and of course even lower on a bike with small wheels. I have thought about someday getting a Moulton bike with 20 inch wheels if I like the performance of the ShareRoller.
I think they can get by with a smaller and lighter motor because the position at the outer edge of the wheel gives it much more torque and allows the motor to run more efficiently at higher RPMs. It is effectively like having a mid drive running a 4-5 inch gear on a bike. Every inch of rotation at the circumference of the roller equals one inch of forward travel, no matter what size tire/wheel you are using.
Without actually trying it out, it is difficult to know if it causes undue tire wear or damage, or if the weight unduly affects handling. I will report on my actual experience when my unit arrives. Court did give Version 1 a 9.5 out of 10 rating here:
http://electricbikereview.com/shareroller/version-1/ but in an email, the developer, Jeff, shared how he really needs to get a newer version over to Court for a review since the product has improved so much since the first version and is quieter and lighter now.
If it works well, it could be bring the benefits of electric assist to a much bigger audience, so I am hopeful that they really have solved some of the problems with other friction drives that have been produced.
