kommisar

I am thinking about building a rear wheel for a road bike. I realize that because of the dish, the NDS spoke tension will be significantly less than the DS tension. Obviously an OC drilled rim can reduce the differential but currently these rims are 3x as expensive as a traditional rim. I have also read that using lighter spokes on the NDS can make the wheel stronger. I can't figure out why this is true because the tension will necessarily be the same regardless of diameter. Does using lighter butted spokes on the NDS along with strait gauge on the DS really make a difference? Or is this another urban legend?

Andrew R Stewart 

Thinner spokes have more elasticity and will stretch more for the same tension. Thus as the rim is compressed in to the hub (from the weight and ground contact), or as the wheel is flexed laterally, the thinner spokes will be less likely to loose all their tension and their nipples less likely to unscrew bit by bit. This same principle is why many wheel builders like to use butted spokes.

This is a method that is as old as tensioned spokes are. Andy

KerryIrons

The general rule for building a good wheel is "never" use straight gauge spokes. As far as using different gauge for left and right, it won't make much difference. Certainly not something to chase around for.

79pmooney

I'm a big fan of using 1) butted spokes and 2) a gauge heavier butted for the right rear. Usually I use the same spokes for front, left rear and right rear of fix gear wheel with little dish. Cassette wheels always go a gauge heavier. I've been doing this 40 years. It works. Using the same spokes left and right on dished rear wheels means either the right side is pushing too tight, running the risk of popping spoke heads, breaking the hub flange or cracking the nipple seats on the rim or running the left side spokes too loose, chasing tighten and true for the life of the wheel and perhaps breaking spokes from uneven tensions as some unwind. If you build the wheel perfect - it works. But I would much rather have a wheel that does just fine 5% tighter or looser than "ideal" and runs trouble free.

kommisar

This what I don't understand: how can spoke cross section effect tension at all? The lateral vector of tension between DS and NDS has to balance when the wheel is at rest. I just don't understand how making the NDS spokes lighter changes this fact.

79pmooney

It doesn't. What causes much of the damage is the spoke going loose when the rim to hub distance shortens (as you go over a bump, say) and the spoke goes completely loose. So a lighter spoke must be stretched out more to achieve the same tension. The spoke that is stretched more will still have some tension after the rim-hub distance is shortened by a given amount instead to going fully loose.

At the point of build, you are right. The lighter spokes get tightened to exactly the same tension as heavier ones would. It is thousands of mile later that the lighter spoked wheel shines because those light left-side spokes have never gone loose while heavier ones might have gone loos momentarily tens of thousands of times (especially under a heavier rider).

ThermionicScott 

It's unfortunate that we use the term "stronger" to describe wheels, because that leads one to intuit that thicker and heavier parts would do the job better. What we want are wheels that will support the load without going out of true, for as long as possible. Since thin double-butted spokes stretch more, they not only maintain their tension better, but are kinder to the rim, reducing the chance of cracks. So they are a better choice, especially for rear wheels. Perhaps we should be talking about wheels that are more "durable" or "resilient" rather than "stronger."

kommisar

Got it. So I am going to go double butted spokes for both DS and NDS as someone mentioned upthread.

Trakhak

And as suggested by 79pmooney above, consider using lighter-gauge spokes on the NDS.

Andrew R Stewart 

"durable" or "resilient" Two terms that have very important contributions as to how our bikes feel and last, which unfortunately have fallen out of favor. Andy

Bill Kapaun

Your Examples?
Velocity lists the A23 @ $96 and the OC version @ $106.
https://www.velocityusa.com/product/rims/a23-622
https://www.velocityusa.com/product/rims/a23-oc-622

kommisar

CR18 is $30 on evil bay.

kommisar

why?

Trakhak

Because wheels work best when the tension required for a spoke in a given wheel build matches the spoke manufacturer's recommended tension for that spoke as closely as possible. The manufacturer's recommended tension for a lighter-gauge spoke is lower than that for the equivalent heavier-gauge spoke, which dovetails nicely with the NDS spokes being of necessity at a lower tension than the DS spokes.

Andrew R Stewart 

I don't think I have ever seen spoke manufacture tension suggestions/limits, rims sure, hubs WRT lacing/cross pattern sort of. But I cant say I've heard of a spoke brand stating limits.

Can you link to a site which does?

Having said that I do agree with choosing spokes that are "balanced" with their job. Most of the time this is more rim strength/stiffness and spoke count dependent. Andy

cyccommute 

I’d go further and say that even spoke tension limits for rims is hard to find. You can find “ranges” but nothing that is concrete nor that suggests the values have been measured. Velocity, for example, suggest 110 kgf to 130 kgf for all its rims. The same spoke tension range is given for the 450g A23 to the 650g NoBS. There’s more information on tire size ranges…something that I consider mostly useless…than on spoke tension ranges.

ign1te

For someone building their first wheel, I'd recommend 2mm straight gauge spokes. More importantly, what type of wheel building equipment do you have? Truing stand? Dishing tool? Tension meter? Spoke ruler? Nipple wrench?

kommisar

Rear wheel for a road bike. The largest tire that can fit in between the chainstays is a 700x28 so this is a smooth road only kind of bike. The rider is 100-110kg. It will be built to a 36H cs-rf3 hybrid hub. I have a truing stand, dishing tool and a spoke wrench. My tension measuring tool is a violin tuner that can detect the frequency of a plucked spoke.

Andrew R Stewart 

Back in the early 1980s my cousin, John Allen, penned an article (in Bike World) about using pluck tones to both true and gage spoke tensions in a wheel. It had too much math for me to follow, even though I understood the principle. IIRC he offered a rough chart for spoke gages and pluck tones and their aprox tensions for the typical road bike spoke lengths common then. Andy

kommisar

This page is the reference I use for ear balling spoke tension:

https://www.sheldonbrown.com/spoke-pitch.html

Jtravels

Andrew R Stewart 

"ear balling"

This is a great phrase! Andy

csport

Not directly, but I have heard that the spoke tension should be around 1/3 its yield stress (e. g., this article by Jobst Brandt), and Sapim cites their spoke strength. For example, for a D-Light it is 1370 N/mm2; the yield stress is 2930N, and 1/3 of it is roughly 100 kgf. It is 118 kgf for the Force and 130 kgf for the Strong.

Jtravels

There is nothing inherently wrong with a straight gauge spoke, provided u buy a quality one like a Sapim or similar. My preference is definitely butted butted... The Sapim Force triple butted is by far the best value for the money. Well worth the trivial amount of added cost.
Anyone with a reasonable amount of patience can build a bike wheel and do a fine job. A wheel stand is not needed, you don't need attention meter. Ignore a good deal of what you read on the internet and just sit down and make your plan. You sure you can make mistakes, everyone does eventually. But riding 'your own' is a happy experience.
o

Andrew R Stewart 

I don't think Brandt said this ("should be"). "Because spokes are usually tensioned no higher than 1/3 their yield stress" (cut and paste from the link) is the reference I see. And the word "usually" is the difference I point out. Some might read this is semantics but there's a large space between should and usually. My first copy (I leant that one to a coworker to never see it again) of his book was a long time ago. Replaced by a later edition. I do agree with the end goals he tries to explain. I do take some issue with the path he choose to take to teach it. This book did set a foundation of discussion that has lasted decades, a very worthy accomplishment.

I have no issue with using 1/3 of max strength as a max wheel build tension. If the rim and nipple/rim interface can handle it. Since most spokes break from fatigue and not exceeding tensile strength, and many rim/nipple interfaces are problematic (spoke bed cracking, nipple/rim friction/corrosion) reducing the spoke tension achievable, I consider raw spoke strength to be a minor aspect. Andy