Spoke pattern/truing question.

[Rusty Nails]

I have just bought a used bike with a spoke pattern of 7 radial spokes on the non-drive side and 14 2-cross on the drive side (all straight pull). I had to replace one of the radial spokes which was broken and am finding it difficult to true the wheel. I have built a few wheels and trued many with no problems but this one is causing me huge problems.

I have a few questions:

Is there any difference in technique in truing such a non-uniform spoke pattern wheel, compared to 'normal' patterns with an alternating spoke count?

Some of the spokes feel much too tight to adjust further. Should I just loosen all spokes and start as if I was in the middle of building a wheel?

Is such a spoke pattern done for mechanical or aesthetic purposes?

 

[Yellow Saddle]

That spoke pattern has no origin in engineering. It comes straight out of the marketing department, invented during a Christmas piss-up. It is nonsense.

Anyway, you are stuck with it, so why not fix it.

First thing to remember is that the left side spokes have to have twice the tension of the right hand spokes because there are 1/2 as many of them. Further, a 28-spoke wheel has super high tension as it is, so this is in another league.

Before turning any spoke, loosen it, oil it (with EP90 oil if you have handy) and only then work on it. Also, flag each spoke you intend turning with a piece of tape and make sure you don't leave it with wind-up. In other words, make one full turn (or whatever) and then back off about 80% to get the flag in its starting position. Hopefully you would have advanced the tension somewhat.

If you have messed it up completely, don't panic. Take a deep breath and have a beer.

Now back off all the nipples to a known point (say 3 turns below the start of the threads or whatever). Now get the left side up to tension until you can hear a nice "ping" when the spokes are plucked. Higher than middle C, if you have such skills.

Now only bring the right side up to tension. When you cannot turn them enough to bring the wheel into dish, loosen the left spokes. This reverse technique helps you get proper tension in the left side.

It is ridiculous, but see it as a challenge.

Let us know how it went.

 

[I like Skol]

Where do you get a hub with such flange drilling and also a rim with 21 eyes?

 

[Yellow Saddle]

Where do you get a hub with such flange drilling and also a rim with 21 eyes?

Trust me, this shoot exists.

 

[Rusty Nails]

It's a Fulcrum Racing Sport DB wheelset which I've been told is OK but nothing special.

@Yellow Saddle, that explains why I was worried about the tension in the 7 left spokes. I have a tin ear but will try to follow your tips at the weekend, which is my first opportunity.

I suspected the spoke pattern was for show rather than purpose, but didn't know enough about spoke pattern to say.

 

[raleighnut]

It's a Fulcrum Racing Sport DB wheelset which I've been told is OK but nothing special.

@Yellow Saddle, that explains why I was worried about the tension in the 7 left spokes. I have a tin ear but will try to follow your tips at the weekend, which is my first opportunity.

I suspected the spoke pattern was for show rather than purpose, but didn't know enough about spoke pattern to say.

I've got a similar set on my TT bike, Roval Classique Pave.



allegedly the 2 cross on the drive side is for power transmission (radial spokes are bad at this)

 

[Rusty Nails]

I've got a similar set on my TT bike, Roval Classique Pave.

View attachment 503404

allegedly the 2 cross on the drive side is for power transmission (radial spokes are bad at this)

No good for me then as I don't transmit much power.

 

[midlife]

Delving in the back of my garage there is a 70's rear wheel with radial spokes on the non drive side and crossed spokes on the drive side....... Not sure why but it made me faster on my time trials

 

[I like Skol]

I suppose they are light. Radial spokes are short so this saves weight where there is no need for power transmission (as in a rear wheel) or braking in a disc brake wheel

 

[Yellow Saddle]

Delving in the back of my garage there is a 70's rear wheel with radial spokes on the non drive side and crossed spokes on the drive side....... Not sure why but it made me faster on my time trials

Well, at least the builder or the "designer" of this wheel understood the physics of such an arrangement. It is possible to have radial on the left of a rear wheel but not on the right, unless the hub has a significant diameter. Those days the hubs were very slender in the centre and could not transmit torque from one flange to the other. That wheel relies on torque applied to the right side spokes only.
Recently Mavic produced a wheel with radial on the right, but it had to beef up the hub to ridiculous dimensions. The marketing blurb for that rationale was interesting, to say the least. I wish I had preserved a copy of it.

 

[Spoked Wheels]

That spoke pattern has no origin in engineering. It comes straight out of the marketing department, invented during a Christmas piss-up. It is nonsense.

I loved that comment

 

[Rusty Nails]

Had a half-hour to spare so started on the spokes and found out why it has been so difficult to true. I put tape on some of the spokes as @Yellow Saddle suggested and as I turned the nipples the spoke turned as well - a problem you don't get with J-bend spokes.

Before doing any more work I am going to put lubricant into the nipples and see if that frees them up a bit.

Lesson to self ...don't buy any wheels with straight pull spokes in future.

 

[Yellow Saddle]

Had a half-hour to spare so started on the spokes and found out why it has been so difficult to true. I put tape on some of the spokes as @Yellow Saddle suggested and as I turned the nipples the spoke turned as well - a problem you don't get with J-bend spokes.

Before doing any more work I am going to put lubricant into the nipples and see if that frees them up a bit.

Lesson to self ...don't buy any wheels with straight pull spokes in future.

Rule no 1. Never try and work with unlubricated spokes and nipples. Lube the spoke thread before putting the nipple on and, lube the inside of the rim hole where the nipple contacts the rim. For the latter, a cotton bud works well.

You say the spokes turned, but did they turn completely or did they just wind up? You can hold a spoke with a pair of pliers but never, ever allow it to slip inside the pliers. The resultant scratch will cause a stress riser and eventually the spoke will break there. The break will look like a clean laser cut.

Keep on trying, it is a nice challenge that will teach you a lot, including how not to design wheels.

 

[SkipdiverJohn]

Trust me, this shoot exists.

Obviously it does, but it begs the question; why on earth would anyone spec a wheel like this?. You'd only have to ping one spoke out on the road and you'd be completely bolloxed. No redundancy.

 

[Yellow Saddle]

Obviously it does, but it begs the question; why on earth would anyone spec a wheel like this?. You'd only have to ping one spoke out on the road and you'd be completely bolloxed. No redundancy.

Why? Because fools and their money are easily parted.

People buy all sorts of stuff based on pseudo-scientific claims such as:
Lighter wheels are better.
Bicycle tyres with grooves work better on wet roads.
Chains with X stamps on the sideplates are eXtra strong and resist stretching.
A thinner sole will transfer more force to the pedals than a thicker sole.
Zerts in the frame will dampen vibrations.
Waterproof grease.
Ceramic chain oil.
Teflon coated cables.
Red bikes are 12.8% faster.
Left-side drives are more aerodynamic around tracks which go anti-clockwise.
Stuff in your water makes you faster.
etc etc.

BTW, one of the claims above is actually true.