Pedal Washers

David N. Makinson said:

What is your take on the use of pedal washers to protect cranks?

The problem is that pedals with flat faced spindles will move radially
in their threads. Washers will not arrext this motion so as the pedal
wobbles in place, it will either begin eroding the washer, after which
it will find a preferred position and cause the same damaging motion
between it and the crank, or it will do this from the start. As long
as there is relative motion of the pedal spindle and the crank, the
crank will be eroded and develop cracks.

The history of automobile lug nuts, that once had this affliction
before being made with a conical pressure face shows what the remedy
is. Short of that, I see no solution to the problem other than some
clever machining:

http://www.chiark.greenend.org.uk/~damerell/bikes/brandt-cranks.jpg

Jobst Brandt

Quoted message said:

David N. Makinson said:

What is your take on the use of pedal washers to protect cranks?

The problem is that pedals with flat faced spindles will move radially
in their threads. Washers will not arrext this motion so as the pedal
wobbles in place, it will either begin eroding the washer, after which
it will find a preferred position and cause the same damaging motion
between it and the crank, or it will do this from the start. As long
as there is relative motion of the pedal spindle and the crank, the
crank will be eroded and develop cracks.

The history of automobile lug nuts, that once had this affliction
before being made with a conical pressure face shows what the remedy
is. Short of that, I see no solution to the problem other than some
clever machining:

http://www.chiark.greenend.org.uk/~damerell/bikes/brandt-cranks.jpg

Jobst Brandt

OK. I understand. And I suppose the tapered washer is split so that it
clamps to the pedal spindle. Did this solve your 1/yr crank breakage
problem?

David

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Quoted message said:

David N. Makinson said:

What is your take on the use of pedal washers to protect cranks?

The problem is that pedals with flat faced spindles will move radially
in their threads. Washers will not arrext this motion so as the pedal
wobbles in place, it will either begin eroding the washer, after which
it will find a preferred position and cause the same damaging motion
between it and the crank, or it will do this from the start. As long
as there is relative motion of the pedal spindle and the crank, the
crank will be eroded and develop cracks.

The history of automobile lug nuts, that once had this affliction
before being made with a conical pressure face shows what the remedy
is. Short of that, I see no solution to the problem other than some
clever machining:

http://www.chiark.greenend.org.uk/~damerell/bikes/brandt-cranks.jpg

Jobst Brandt

Jobst,

1. What's the angle countersink?

2. Where did you get the angled washers?

I've used washers on TA and Stronglight cranks. They have a slight
counterbore for a washer and at one time the washers were provided by
the crank manufacturers.

Chas.

David N. Makinson said:

Quoted message said:

Quoted message said:

What is your take on the use of pedal washers to protect cranks?

Quoted message said:

Quoted message said:

The problem is that pedals with flat faced spindles will move
radially in their threads. Washers will not arrest this motion so
as the pedal wobbles in place, it will either begin eroding the
washer, after which it will find a preferred position and cause the
same damaging motion between the washer and the crank, or it will
do this from the start. As long as there is relative motion
between pedal spindle and crank, the crank will be eroded and
develop cracks. Look at the face of any well used crank when the
pedal is removed.

Quoted message said:

Quoted message said:

The history of automobile lug nuts, that once had this affliction
before being made with a conical pressure face shows what the
remedy is. Short of that, I see no solution to the problem other
than some clever machining:

http://www.chiark.greenend.org.uk/~damerell/bikes/brandt-cranks.jpg

Quoted message said:

OK. I understand. And I suppose the tapered washer is split so
that it clamps to the pedal spindle. Did this solve your 1/yr crank
breakage problem?

This question gets asked often. No, I have not had any crank failures
since installing this modification and am using the same DuraAce
cranks that were all bought at the same time. These are as the
picture shows, the same old style Shimano square taper cranks.

I also no longer inspect the cranks with a magnifying glass before
going on longer rides on weekends as did in the days when I broke at
least one crank per year for close to two dozen cranks.

Jobst Brandt