An original rotor on the right with no rivet, and an aftermarket on the left with round-headed rivet. Note that the rotor on the left is from an aftermarket electronic ignition system and has an extended base containing magnets to trigger a Hall-effect device.
Showing the rivet inside the circle of the base i.e. too close to the distributor shaft and hence prone to breaking down.
Another style of currently available rotor. Still with the round-headed rivet but fitted outside the circle of the base i.e. further away from the distributor shaft and so probably 'safe'.
This rotor from a 25D4 has a domed rivet rather than flat and looks to be positioned slightly further out than the top rotor, but not as far out as the one immediately above. This failed in service within hours of being fitted (ironically as a result of the loss of the carbon contact in a nearly new cap that had damaged the also nearly new rotor), firstly causing intermittent 'fluffing', before total failure. The good news is that the owner was demonstrating the fluffing to his mechanic when it totally failed, and he (the mechanic) had come equipped with a new one. The bad news is that it chose to fail on a very busy road with traffic flowing at motorway speeds but no hard-shoulder. Fortunately it was a quick fix to drop in the new rotor. Photos David Bolton.
A 'red' rotor from Distributor Doctor, with improved insulation material and no rivet ...
Note that a number of manufacturers have jumped on the bandwagon and are producing red rotors, but several have the same problems as before. For that reason Dist. Doc. embosses his with 'DD', but presumably that is not beyond faking either!