Originally Posted by cyclotoine

You could probably make the Lotus work with a high stem and saddle, but it might look and feel funny. The top tube is probably not that much shorter than the other bikes. I can tell you that the seller is just plane wrong. I can tell that is a one piece headlug with was common in the 1980s on many manufactures smallest frames. I have seen it many times and it usually measures out to a 49cm frame center to center. Which looks like a 51cm c-t which is like 20 1/8".. if the guy was not precise and measured to the bottom of the bottom bracket he likely got "About 21"... Easy to see how that could happen, but for sure the lotus is no bigger than a 50cm c-c frame. The angle is bad and there are some wires wrapped up there so I could be wrong, but I am fairly confident.

Edit: According to the specs they came in 48 and 51. It will bet it is one of those two size.

Schwalbe might still have decent tires in 27" too, but the selection, when compared to 700, is severely limited. I would run 27" until the rims are shot.