While there is no question that the quality of many vintage bicycle components is superior to that of their modern day mass-produced counterparts, vintage components do fail.  Some failures are caused by design flaws, some are simply the result of fatigue and use over the decades, some are caused by improper adjustment or retention, and some by corrosion and exposure to the elements.  How can you determine when it is safe to continue using a vintage component?

1950’s Lyotard pedal thread failure, compared to newer 1970’s model on the right.

Sometimes, you can’t.  While I was removing the 1950’s Lyotard Marcel Berthet pedals from a recent project, a small chunk of the threads from the left side pedal spindle simply fell to the ground.  This was after I had taken a test ride, before overhauling the pedals.  What if the spindle had broken during my ride?

Before I disassembled the pedals to examine them, I did some sleuthing.  I wanted to know how one can spot flaws and weaknesses in components before disaster strikes.  I found a good overview of metal fatigue failure at Open University’s Component Failure Museum.  There is a  specific section on their web site for bicycle component failures, including some interesting and scary crank arm, brake, and steel frame failures.  Metal fatigue results in a sudden, catastrophic failure after the initiation and growth of a crack at a stress point.  Is it possible to diagnose such a crack with the naked eye?  Perhaps not if you are not a trained materials engineer.  But, with some basic understanding of cycling mechanics and physics, at least one can know where the highest stress points are for a given component.

In this case, I wanted to know the highest stress point for a pedal spindle.  And, I wanted to know if Lyotard pedals in general, and Marcel Berthet pedals in particular, have had a history of spindle failure.  As it turns out, the answer is YES and NO.  Some Lyotard pedal spindles (namely model 460D) appear to have a history of sudden failure where the spindle breaks in the middle of the thickest part of the spindle, with no warning.  This particular model was ubiquitous in the 1960’s and 1970’s – I have accumulated a number of these pedals in a shop bin.  Some of the cages of these pedals have come apart, or are loose, so I haven’t re-used them and keep them around for parts.  Their spindles all look great, but that, as it turns out, may mean nothing, because the design of the 460D pedals, with their flimsy aluminum cages, may be the actual culprit.  However, the location of the failure on these pedals spindles gives a clue as to their highest stress point, which appears to be closer to the crankarm side of the cage.  Fortunately, I have never experienced a pedal failure while riding.

The highly regarded Marcel Berthet pedals have steel bodies, and shorter spindles than the 460D pedals.  Based on my research, that means they are less susceptible to failure. Steel and aluminum can interact badly with each other over time in a process called galvanic corrosion, so steel cages with steel spindles are a plus.

The above photo shows the early 1950’s spindles, compared to their mid-1970’s counterpart.  You can see that the manufacturing process changed, and that the newer spindle looks pristine.  On the older spindles, there is brass residue below the base of the cone portion, and I am not sure why.  There are also grooves and striation marks in the area between the brass material and the cone section, as seen below.

What does this mean?  And, why did the threads fall off upon removal of the pedals from the crank arm?

1950’s pedal spindle

1970’s pedal spindle

I think I know the explanation for the thread failure.  The 1950’s spindle has a very deep angled inset at the threaded end of the spindle, whereas the newer version has a much less deep inset.  I think the threads failed simply because there is not a lot of material at the end of the threaded portion.  When the weight of the pedal pulled it down from the crank arm as I was removing it, the threads broke off.  I think the spindles may be just fine, and there are plenty of good threads left to allow re-use of the spindles.  Fortunately, the cones and pedal bodies are still in good shape.

Based on some additional research, I have decided to clean and polish the spindles before reuse, photograph them, then plan to overhaul the pedals with greater frequency and examine the spindles during each overhaul to see if there are any changes to the appearance of the spindles.  While this might seem paranoid to some, it’s my well-being and perhaps that of a future owner of these pedals that is on the line.

Last Sunday, I witnessed a cycling accident that involved a rider on a new (I learned) bicycle.  She was unaccustomed to the quick response and grabby strength of her new braking system – short reach sidepulls – which have a lot more mechanical advantage than pretty much most vintage calipers.  She needed to slow down quickly, applied her brakes, and was propelled over the front of the bike, headfirst.  She was not wearing a helmet, and was pretty banged up.  This was another reminder of the importance of understanding all the elements of the bike you are riding.  Cycling is not the same as driving a brand new high tech car.  All cyclists need to be alert to safety issues involving their components, frames, and riding styles.