Brake lever cotters

[Tony Griffiths]

Fitting-up the cotters is, as Ruairidh says, important. Why is it necessary to “fit-up”? Because of poor quality pattern parts. Let’s assume that original, Austin-made brake cams, cotters and brake arms would all assemble with ease - and need just a hammer strike on the cotter to bed it in. On a mixture of all-new, or old and new parts, the tolerances might give an Austin-quality fit - though it's more likely that the cotter will a) go straight through or b) hardly go in at all.  For example, upon checking three new (old stock) brake cams, the depth of the "cotter cut-out" in their shaft was found to vary, these being, respectively: 0.311”, 0.323” and 0.331”.  Now, while the difference between the deepest and shallowest is “only” 20 tho, this is sufficient, in the case of b) to require the cotter to be carefully filed. Should the cotter pass right through, or go in so deeply that a pile of washers is needed behind the nut, the only recourse is either to find a better cam -  or modify the cam by silver soldering a piece of thin steel to the bottom face of the cut-out - and then filing it until the cotter fits, not something that you would want do (unless you’re an ace at silver soldering) a few hours before departing for some competition.
Interestingly, the new "concentric" cotter shown below has its thread on the centre line of the full diameter and - having assembled everything on the bench before fitting to the car - works perfectly. Some pictures for your amusement and discussion....