Spoke orientation for disc brakes

[Michael]

I recently read that Barnett's Bicycle Manual recommends a certain spoke orientation for wheels with
disc hubs. They state that the major disc brake manufacturers don't specifically require this
orientation, but they recommend it. They also note that the orientation is what their wheelbuilding
instructions follow.

I recently had a wheelset built up for disc brakes (700c wheels, if it makes a difference), and the
spoke orientation appears to not follow Barnett's recommendations, if I understand them correctly.

Is it common to follow these reccomendations? What's the likely outcome for wheels with reversed
orientation - going out of true? broken spokes? spokes pulling through the rim? nuclear war?

Here's the blurb from chapter 37 about disc brakes:

"The recommended cross patterns are limited to 3x and4x. Deceleration can occur much more rapidly
than acceleration, so consequently the tornsional loads from deceleration are much higher than those
generated during acceleration. The recommened cross patterns are required to transfer the higher
torsional loads that hub-mounted brakes can generate during rapid deceleration.

"Although Hayes makes no recommendation regarding lacing patterns, other manufacturers require that
the left-side head-out spokes radiate clockwise from the hub and that the right-side head-in spokes
radiate counterclockwise from the hub. These are the same directions that result from following the
wheel-lacing instructions in this manual. The vernacular terms for these patterns are that the
'pulling' spokes are "head out" and the "pushing" spokes are 'head in'. An alternate term to
'pulling' is 'trailing' and an alternate term to 'pushing'" is 'leading'."

TIA, Michael

 

[Jobst Brandt]

Michael Press writes:

> I recently read that Barnett's Bicycle Manual recommends a certain spoke orientation for wheels
> with disc hubs. They state that the major disc brake manufacturers don't specifically require this
> orientation, but they recommend it. They also note that the orientation is what their
> wheelbuilding instructions follow.

> I recently had a wheelset built up for disc brakes (700c wheels, if it makes a difference), and
> the spoke orientation appears to not follow Barnett's recommendations, if I understand them
> correctly.

> Is it common to follow these recommendations? What's the likely outcome for wheels with reversed
> orientation - going out of true? broken spokes? Spokes pulling through the rim? Nuclear war?

No, and no. Spoke orientation is an old bugaboo, similar to ankling, that also has no merit.

> Here's the blurb from chapter 37 about disc brakes:

> "The recommended cross patterns are limited to 3x and4x. Deceleration can occur much more rapidly
> than acceleration, so consequently the torsional loads from deceleration are much higher than
> those generated during acceleration. The recommended cross patterns are required to transfer the
> higher torsional loads that hub-mounted brakes can generate during rapid deceleration.

That is also untrue and has not been analyzed by these folks or they wouldn't say these things.
There is an analysis of this in "the Bicycle Wheel" that shows what the spoke loads would be for the
torque needed to climb a vertical wall, if that were possible. This was done mainly so that relative
forces could be compared, they all being the weight of rider and bicycle. The forces are small
compared to those that just rolling along on the flat causes the load bearing spokes to go through.

> "Although Hayes makes no recommendation regarding lacing patterns, other manufacturers require
> that the left-side head-out spokes radiate clockwise from the hub and that the right-side head-in
> spokes radiate counterclockwise from the hub. These are the same directions that result from
> following the wheel-lacing instructions in this manual. The vernacular terms for these patterns
> are that the 'pulling' spokes are "head out" and the "pushing" spokes are 'head in'. An alternate
> term to 'pulling' is 'trailing' and an alternate term to 'pushing'" is 'leading'."

Yes, its all hocus-pocus. I don't understand why people should believe this stuff when there no
reasons are given why this should be beneficial and no explanation of how great the forces are.

Jobst Brandt [email protected]

 

[Jim Beam]

for what it's worth, shimano specify the same spoking pattern as your barnett's extract for their
disk hubs. generally, i give shimano credit for knowing what they are doing on most of their other
stuff, so they must have a season.

on the other hand, it's commonly ignored with apparently few ill effects. flip a coin and make your
choice like that!

jb