Regardless, the Record was a big step up from the Gran Sport in terms of smoothness & precision. Using toothed plastic rollers was part of the reason why. BTW, I've worn out more rollers than I've cracked. That said, I think they all crack eventually because over time the plasticizers in the rollers (and in most plastic objects) go away, so they shrink & get brittle. Sunlight, petroleum lubes & ozone may also have something to do with it, either directly or by encouraging the plasticizers to take a hike.

Still, if a Gran Sport turned up in my bed, I wouldn't make it sleep in the garage.