[MrFlippant]

A unit like the Proses is better than nothing at all, but I'd like to make sure potential buyers are aware of the following:

1 - It's risky to use a machine like this for digital cars. If you are not VERY careful to never apply too much resistance to the tires during the process, you may cause the motor to draw too much power, and actually damage the digital chip. If you decide to use this machine for a digital car, it would be best to temporarily disconnect/remove/bypass the chip so that the car is functionally an analog car. For DPR cars from Scalextric, you can swap the chip for the analog plate. For a Carrera digital car, you can open it up and disconnect the wires that go from the braids to the chip and from the chip to the motor, and connect them directly together, completely bypassing the chip. At least this way, you won't damage the chip... you may only damage the motor...

2 - you're not actually truing the wheels/tires with this, you're making a smoother egg... unless you have the steady hands of a brain surgeon and the patience of a saint. This is because there is little to no control of the height of the wheels/tires off the sanding surface other than by your own hand. To properly true a set of tires, they must be held at a set distance from the sanding surface, in an immovable way, and with fine control over that distance so that it can be reduced in fine increments as you take off the high spots. Without that level of control and stability, you're really just scuffing things up, not truing them, which is not the same thing.

3 - ideally, a "mule" chassis or two should be used, so that you are not reducing the life of the motor in the car you actually want to race by running them at a constant high speed with a high amount of resistance created by the tires going against the sanding surface. While this should be kept to a minimum to do a good job, anyway, it's still an undue amount of wear and tear on the slot car motor and gears.

Now, all that said, I know guys who can use a tool like this to get great results. I just want people to know the difference between a machine like that, and one that is dedicated to the purpose of making the tires actually true, which is to say that they are perfectly round and concentric to the axle. And sometimes, for a lot of us, a nicely scuffed up, mostly round and smooth tire is good enough for the fun of running the car around and having a few races. Those in competitive clubs will probably want something different, and hopefully an Area3/Tire Razor/RSM type machine hits the market again soon.