Bibendum /semi creux
These were produced only in the metric diameters of 40, 45 and 50cm between 1928 and and many cars which originally used them have been converted to normal inch size rolled edge rims. Now that originality has become more appreciated many owners are wanting to fit these unusual rims again.
For this reason we developed the rather complex tooling to produce these rims again with, so far only in 45cm diameter. It was an interesting technical exercise but they have proved quite expensive to produce.
We have however recently acquired a stock of original Bibendum rims in 40, 45 and 50 cm diameters and can use these to build and rebuild almost all the original designs.
We were puzzled for many years about why Michelin made these strange rims. None of the explanations we heard made real sense. Finally we found a French publicity article explaining the whole concept.
Prior to this the choice was between beaded edge tyres which has elastic edges and needed high tyre pressure to be kept in place (uncomfortable ride) and wired inelastic edge tyres which could be run at lower pressure (more comfortable ride) but had at first needed removable lock rings to allow them to be put on the rims.
Then in 1924 Dunlop introduced the drop centre or well based rim so the wired tyre bead could be placed in the well on one side of the rim and fitted over the opposite edge.
In 1928 Michelin must have seen an opportunity to cash in on safety fears that in case of a puncture the tyre could drop into the well and find the same way to come off the rim as it went on. Hence they came up with the ‘semi creux’ or half well rim with the cunning addition of a blocking plate held in place by the threaded valve of the inner tube which was arranged to be in the centre of the tyre well and would not allow the tyre to drop into the well so it couldn’t come off. To remove the tyre the valve needs to be unscrewed and pushed out of the way to allow the tyre to drop into the well. Michelin cunningly made the rims in metric sizes so that normal inch sized tyres couldn’t be used on their rims.
Other manufacturers did eventually make metric tyres to fit these rims when they proved to be so popular but Michelin got a good head start.