Wheelbuilding myths debunked

[Biggsy]

I've never understood why, when crossing spokes, some builders pass them "wrong side" of each other so the spokes are touching and curved. This must detract from the overall strength, surely? It looks particularly bad on small wheels.

It's normal for spokes to touch and curve at the crossings.  This lacing spreads load and increases lateral strength, and helps to prevent spoke-loosening.

Without this, there wouldn't be any point in crossing the spokes besides the angle being less stressful for the hub flanges.
EDIT: and to transmit drive torque, and braking torque with disc/hub brakes.

[deliquium]

(6) at last!  Someone else says it!   

Definitely - but there are some folks out there - and you all know who you are (well thumbed stained JB book under the bed) - like bending over bicycle wheels and scratching sometimes imaginary beards whilst going hmmm 

Although I guess there might well be a case for disc brake wheels  ?

[Arno]

Uncrossed spokes will make a cleaner passage through the air than crossed. As the spokes at the top of a wheel will be travelling somewhat fast than the bike, this may be significant.

Will the cleaner passage through the air be noticed at the crossing point (or, for radial spokes, where the crossing point would have been), or through the length of the spoke? Much of the spoke length is already sheltered behind the rim, and there's probably a fair bit of turbulence created by the fork blades. So how much difference is the presence or absence of a crossing point really going to make?

ISTR that something over 90% of the aerodynamic drag experienced by a cyclist is due to the size and riding position of the cyclist, so messing around with spoke counts and crossing patterns seems a little silly.

I think uncrossed / flat spokes do make sense on some recumbents where the rider position is quite aero, especially with a fairing or tailbox, when riding at over 30km/h

[deliquium]

I love it. Every "club" has their "myths".

Every club has its shared passions transcending gender race politics and even religion? etc

The good thing about YACF is the diversity and ability to laugh uncontrolably at each other and enjoy a good thing

[deliquium]

Ooops!

Is it a matter of three strikes and out - if one diverts off topic utilising a foreign left sided pond metaphor? 

[orienteer]

I've never understood why, when crossing spokes, some builders pass them "wrong side" of each other so the spokes are touching and curved. This must detract from the overall strength, surely? It looks particularly bad on small wheels.

It's normal for spokes to touch and curve at the crossings.  This lacing spreads load and increases lateral strength, and helps to prevent spoke-loosening.

Without this, there wouldn't be any point in crossing the spokes besides the angle being less stressful for the hub flanges.

I thought the primary point of crossing was to transmit drive torque, and braking torque with disc/hub brakes.

[Biggsy]

I thought the primary point of crossing was to transmit drive torque, and braking torque with disc/hub brakes.

I forgot those good points, but the other points apply as well.  Good front non disc/hub front wheels are also laced in the same way for the reasons I mentioned.  Otherwise no-one would bother.

[PeeJay]

Only just noticed this thread....

Just something to add Re 3).

Spokes, like springs, obey hooks law whereby the deflection Vs load graph is a straight line. i.e. The stiffness is constant and independent of the load (tightness).  So once the spoke is tightened sufficiently not to be slack while riding. There is no extra benefit of tightening any further - it does not get any stiffer.

[Biggsy]

"Not to be slack while riding" includes having enough tension in reserve to cope with momentary reductions in spoke tension from impacts to the wheel from potholes etc, as the rim deflects.  So I think it potentially helps to have as much tension as the rim can bear.

[mrcharly-YHT]

Plus the torque from mashing gears out of the saddle. That's  a not-inconsiderable side loading.

[tallsam]

2. Spokes do not fail because they are too tight.  They fail because they are too loose (movement leads to fatigue).  The ultimate tensile stress of a spoke is way above anything the rim can take, and riding the wheel makes them go slacker, not tighter.

Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit. Its all relative. They'll go slack and tight as you ride but its all equal (also if its built right it'll be so minute it won't matter).

[PeeJay]

2. Spokes do not fail because they are too tight.  They fail because they are too loose (movement leads to fatigue).  The ultimate tensile stress of a spoke is way above anything the rim can take, and riding the wheel makes them go slacker, not tighter.

Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit. Its all relative. They'll go slack and tight as you ride but its all equal (also if its built right it'll be so minute it won't matter).

I assume you mean "less tight" rather than "go slack"

[Manotea]

7. You need a special wheel jig and tensiometer to build a wheel.

This is my first wheelbuild (to be fair, a rim transplant) which I built the day before the Elenith 2007. I rode the wheel for about two years (by which time it needed another new rim) with only the most minor of tweaks.

<a href="http://www.youtube.com/v/rXWFJrKjGRk&rel=1" target="_blank">http://www.youtube.com/v/rXWFJrKjGRk&rel=1</a>]

The noise you can hear is vibration from the schmidt dynohub resonating through the workmate frame. Off the workmate, its smooth and silent.

[corshamjim]

That setup looks like it would work better than my cheap purpose-built trueing stand.    I particularly like the tie-wrap guages. 

[Efrogwr]

7. You need a special wheel jig and tensiometer to build a wheel.

This is my first wheelbuild (to be fair, a rim transplant) which I built the day before the Elenith 2007. I rode the wheel for about two years (by which time it needed another new rim) with only the most minor of tweaks.

http://www.youtube.com/watch?v=rXWFJrKjGRk]

The noise you can hear is vibration from the schmidt dynohub resonating through the workmate frame. Off the workmate, its smooth and silent.

That's not a myth; it's total bollocks.
I've got a Var jig. The only advantage is that it is too heavy to move easily. It's supposed to help dish the wheels correctly, but that's bollocks, too.
i got it as part of a job lot of bike tools (very cheap), otherwise i wouldn't bother with it.
You don't even need a fork in a Workmate, although that makes truing a front wheel a lot easier.
Every cyclist already has a truing jig; the bike. I'm not averse to correcting small errors in lateral trueness withe the wheels on the bike.
If you are building wheels for yourself, you may as well true them on the bike. A dishing gauge would be handy, but it is possible to make one yourself.
I'm currently building cheap(ish) dynamo wheels for stock using very basic hubs (Novatech). They're as rough as arseholes in the stand, but reasonably smooth and long lasting (several thousand miles) on the road.

[Tewdric]

Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit.

It's easy to demonstrate that the upper spokes don't measurably change in tension when you place a load on the wheel, whereas the tension of spokes below the hub reduce in tension.  In a static situation in any case! 

[deliquium]

And - there's nothing at all mythical or magical about any ONE wheelbuilder

[andrew_s]

Not strictly true. The spokes nearest the ground will go slack when riding which will in turn tighten those opposite the ground a bit.

It's easy to demonstrate that the upper spokes don't measurably change in tension when you place a load on the wheel, whereas the tension of spokes below the hub reduce in tension.  In a static situation in any case! 

The lowest spokes go slacker because the rim deforms slightly due to the ground pushing against it. Because the lower spokes aren't pulling down so hard the weight on the hub is supported by the unchanged tension in the upper spokes.

[Efrogwr]

I forgot to comment on tensiometers. Biggsy has mentioned getting a feel for the correct tension for your particular wheel. That's all you need. For beginners, bringing the wheel into correct tension, systematically and carefully will ultimately lead to getting the wheel right.
Tensiometers are not like, say, multimeters. They all apparently give different results. You would need to know which instrument, and what rims and spokes were used to arrive at a recommended tension. Then, if you have a tensiometer, you need a well built wheel of known tension to calibrate it.
You can check for evenness of tension by ear.

[frankly frankie]

Or feel.

[deliquium]

Or feel.

  

Once you know the feel

[mattc]

And - there's nothing at all mythical or magical about any ONE wheelbuilder

There's something pretty cool about a blind wheelbuilder.

(although he needs to move somewhere with more kudos than Reading )

[deliquium]

And - there's nothing at all mythical or magical about any ONE wheelbuilder

There's something pretty cool about a blind wheelbuilder.

(although he needs to move somewhere with more kudos than Reading )

Wheelbuilding in Didcot blind or Reading with eyes does not make one a mythical person though?

And hopefully we can all agree that a YACF wheel should have reasonable tolerances?

Tee hee!

[Manotea]

And hopefully we can all agree that a YACF wheel should have reasonable tolerances?

I fear a YACF wheel will pull to the left and, unless corrected, end up in the gutter.

[giropaul]

I inferred that he means that deliberately building wheels with lower tension in the spokes (as has been suggested to me by someone who should know better),..

That person didn't also advocate tied and soldered spokes perchance ...   

Nothing wrong with tied and soldered on the rear wheel of a track bike used by a strong sprinter.

I lent a pair of track sprints, built for a tandem, to the England pair for the Commonwealth Games (they won gold - Geoff Cooke and Tony Brocklehurst). They were returned to me re-built and tied and soldered, the front wheel in a two cross/one radial pattern. They were done by the German team mechanic. Boy, those wheels are solid, and totally bomb-proof, and have survived several crashes since.

I've known several very good wheel builders, and I'm convinced that there are good, very good, and then, not very good, builders. One of the greatest is Steve Snowling who used to work the sixes for Tony Doyle. He tied and soldered (note - not just tied - you have to scape the chrome off chrome spokes, or use rustless, to properly solder the wires to the spoke) some track wheels. Again, they never, ever, went out of true.