Aluminum and steel cranks.

Steve Saines, who regularly comments on my posts, mentioned the elegance of the old steel Stronglight cranks on my Cinelli. I don’t think that there is any doubt that the old cranks were much nicer looking than those of today; however steel cranks have two things going against them: first they are quite heavy, about 50% heavier than a similar alloy one and secondly they wear much faster than the alloy equivalents. As odd as it seems the square tapered hole, which mates with the b/b axle, wears very quickly. The cranks on the Cinelli (mentioned in my last post) have worn so much that a have had to grind about 5mm off the end of the axle to allow the cranks to pull further on. The reason is, I believe, that the aluminum cranks mate much tighter onto the steel axle, the steel bedding into the aluminum eliminating any chance of play. This doesn’t happen with the steel cranks and any slight difference in the mating of the two will quickly develop into wear.
The problem was also common with other steel cotterless cranks. The old Gnutti steel cranks, which fitted to a tapered spline on the axle, were really notorious.

Race leader Ken Russell very nearly lost the Tour of Britain in 1952 when his Gnutti crank came loose on the last stage into London. Belgian rival, Marcel Michaux saw his plight and offered Russell his bike. Russell finished on the Belgian’s bike and retained his yellow jersey.

The only steel cotterless cranks that don’t seem to have had this problem are the old CCM cranks. Maybe it is because the taper on the axle was much steeper, or perhaps the machining of cranks and axles was more precise.

Of course most of the old steel cranks used cotter pins. I don’t think any of us want to go back to those. It seems very few mechanics have the necessary skill to fit cotter pins correctly these days. There were, however, some beautifully made cottered cranks. The British Chater Lea, Williams and BSA were outstanding as were the French Stronglight and Duprat. The Italian Magistroni steel cottered cranks were standard on all the top Italian bikes until Campagnolo introduced their alloy cotterless cranks in 1958. The best of all, in my opinion, were the French Duprat which had hollow steel arms. Their weight was very little more than alloy ones and they were quite elegant.

Recently I have seen steel cotterless cranks on cheap department store bikes and on high end BMX bikes. It would be interesting to know if they stand up well.

Steel chainwheels don’t seem to last any longer than alloy ones either. The thought here is that the chain beds itself into the aluminum to make a precise fit similar to the cranks and axles and very little wear occurs thereafter. This doesn't seem to happen with the steel rings. Another explanation put forward is that road grit gets bedded into the aluminum and forms a very hard surface. Does anyone else have an explanation?

Here are photos of a few cranks in my collection.



Chater Lea.




Stronglight 3 Pin cottered with Simplex rings.




Stronglight cottered 5 Pin.




Stronglight 49d alloy cotterless.




A. Duprat hollow steel cottered.




Bianchi.




Gnutti cottered.




Williams 5 Pin.




C.C.M. cotterless, 1930.




B.S.A.