There's an ali shim sandwiched between the de Dion tube and the ear that the hub assembly bolts on to.

Why is it there?
Do I need to keep it?
What will happen if I don't replace it?

Thanks

My son phoned me yesterday and mentioned that a work colleague of his, a trained mechanical engineer, has ordered his first kit from Caterham. For some reason, the first thing I thought about was those Heath Robinson bits at the end of the DD tube, like a couple of packs of playing cards stuck on there like an afterthought and on which your life depends - that, of course, given that you are not overly fond of rear wheel steering. Just the sort of thing to impress an engineer. Made of nice reassuring aluminium too.

Sorry I can't answer your question, but I would like to know in the first place why those ears are there at all, other than the tube doesn't happen to stick out in exactly the right place for the hole in the bodywork where the wheel goes. Is there any geometric explanation for this arrangement?

As I have a 'live axle' I can't help, but Uncle Albert will be along in a bit with an answer I am sure (that's Chris at The 7 Workshop...)

The De Dion Ears are there to allow you to change your amount of rear camber from Radial to Crossply tyres.
Are think the are 2 options of Ear available from Caterham, 1.25 and 0.25 degree Ears.
Or you could have your own spacers machined up if you required a different setup.

Uncle Albert i am sure will have more detail to add being the 7 Guru

Without the ears the drive shafts would need to be down the centre of the Dedion tube ..... but that arrangement is called a live axle.

So is the camber generated by the Ear (big lump of machined ali that the hub is bolted to) or by the shim (flimsy bit of thin ali that appears to be sacrificial as it suffers badly from bi-metallic corrosion) ?

The camber is usually determined by the ear being machined to a slight wedge although some people have made shims to alter the camber. I seem to recall the soft ally insert is to cover the hole in the end of the Dedion tube.

just to confirm about thin shims ,were used to cap off ends of the d.tube If left off for any reason plug ends of tube or spray waxoyl or similar to stop weather attack to tube

Excellent. Thanks chaps.

If they only to plug the ends of the de Dion tube, then I'll fabricate my own new ones.

Good point about the waxoyl in the tube... I think I'll do that anyway