Spoke Length Question
 

I've run a proposed build through two spoke length calculators (Freespoke and ProWheelBuilders) and came out with rear spoke lengths of 285.4 NDS and 283.6 DS. I'm building with Velocity Fusion Rims. My question is: Can I get by using 286 spokes on both sides (I can get good deals on full boxes) or should I order 284s for the DS?

Another question: Is it true that 2.0-1.5-2.0 double butted spokes are actually less likely to break than beefier spokes due to the increased elasticity of the narrower center section? My current builds have all used DT Comp 2.0-1.8-2.0 but if I can save a few grams without sacrificing durability, or even improving durability of the build . . . well . . . win+win.

You are going to need a wheelbuilder for good imput but IME rounding down works well (don't want to run out of threads), life is short why take a chance to save a few bucks for close (your rim might make a difference), and I can see a better fatigue advantage over the straight gage.

I never have issues using 2 lengths on rear wheels, because I also use 2 different gauges, so need different spokes anyway.

On a typical pair of wheels build I typically use the same (lighter) spokes on the left side rear and the front, and the shorter, stouter spoke on the right rear.

Your question about a strength gain using lighter 2.0/1.5 spokes is tricky, and turns on the definition of strength.

If you're looking to reduce elbow breakage, then yes. But it will be very hard to find tensions on a dished rear wheel such that the right isn't too high and the left too low at the same time. Also, the lighter spoke will allow more lateral flex, and that may offset any advantage.

If you want to go lighter, while producing a 1st class wheelset, use the 1.5s on the front left rear and the 1.8s on the right rear. The reduction in gauge on the left will allow decent elongation at lower tension. By lowering the left's minimum tension, you won't be pressed to bring the right as high.

BTW - the key to spoke length forgiveness is the nipple. Since you want at least 1-2mm thread engagement in the head of the nipple, that means that the shortest spoke you can use will end about 2mm short of the top. If the nipple doesn't allow overrun above the top, then you have a narrow 2mm margin of error in spoke length. If your spokes are long on one side and short on the other, then that 2mm target will be too small for both to land within it.

I carefully seek out nipples which allow plenty of overrun, preferring 3mm. When I'm building hollow rims the overrun provides a 5mm target window (-2mm - +3mm). I don't take advantage by using the same length when I want 2, but it does allow me to aim high, so my finished wheels have full thread engagement into the spoke head.

Do you know where in the nipple those spoke calculators set their target?
If a calc aims for flush with top of nipple, then 2 mm too short will still be OK. 2 mm too long won't leave much margin - if any.
If a calc aims for flush with tool slot, then 2 mm short is supposed to be less than ideal. But 2 mm too long should work.
OTOH you can add a washer under the nipple to increase the ERD on the short side. Kinda counter-productive if you're trying to build as light as possible, but doable.
I'd be a bit wary of an all-1.5 mm build. They're quite stretchy and prone to wind-up. If it's a low-count wheel you might not get the tension needed.
I'll happily use them on the NDS though on most wheels.

Thanks for the answers. I don't mind ordering two different lengths if it makes a better wheel build. I just wanted to know if the 2mm difference in length would matter if I went with the longer spoke. I assumed that the target was to the bottom of the nipple slot, but I don't know that for sure. I'll send them an e-mail to see if I can find out. I've used the DT Swiss Comp 2.0-1.8-2.0 in most of my builds before but had a discussion a while back during which I was told that the increased elongation of the 1.5 butted spokes actually decreased the chances of breaking spokes at the elbow for Clydes like myself. "When was the last time you saw a spoke break in the middle?" was how he put it to me, explaining that as long as the elbow and threaded ends are 2.0 there is no reason not to use 1.5 instead of 1.8 butted spokes.

This is not a low spoke count build. Actually it is two separate builds: The first, described in my original post, is a rebuild of a rear wheel. I damaged an Open Pro rim last season when I flatted on a fairly steep downhill on a rather rough section of road. The 105 hub is only a couple of seasons old. As I weigh about 235# in the off season and this is my training wheelset, I looked for a slightly beefier but not overly heavy rim. The Velocity Fusion came highly recommended but has a smaller ERD than the Open Pro. The build will be a 36H, 105 hub to Fusion rim, so low spoke count is not an issue.

The second build (if I decide to do it) will be 32H, Ultegra hubs with Fusion rims. I'm looking for a reasonably light but Clydeworthy build. I'm not opposed to using DT Swiss Comp spokes if it will make for less lateral flex as I do ride a fair number of winding hilly roads in MN lakes country. If it really won't make a lot of difference to lateral flex, the lighter spokes would be preferred. I'm intrigued by FB's suggestion to use the heavier spokes on the drive side. The only problem I have had with the Open Pros is that the manufacturer recommends rather low (95 kgf) maximum tensions. Even though I run the rear drive side at 115, I still have had occasional problems with NDS spokes working themselves loose (especially the pair that spans the weld). Would using lighter spokes on the NDS help prevent this?

Thanks

You might want to consider a tap, in case you need to make the treads longer on one side.

I don't want to go deep into the details, but this isn't an option, whether you're speaking about the spokes or the nipples.

It might be possible to roll another 2-3mm of thread on the spokes if you have the right tool, but this is both slow and expensive compared to the cost of simply buying the right spoke.

In a pinch, it's possible to drill or ream out a bit of thread in the nipple, to increase the overrun range, and I've done so when nipples acceptable to me weren't available. Otherwise, if only 1mm or so is needed, then adding a washer under the nipple is the easiest option (other than simply using the right spoke).

A minor derailment, maybe, but did you consider using a replacement rim that would allow you to re-use your spokes? I have read that the A23 can be used as a direct replacement for the Open Pro, maybe there are others?

Going by what you read can often be misleading. I often find Velocity rims to be up to 2mm off the published numbers when I measure them myself.
Other manufacturers are frequently not as published either.

I thought about it but decided to go with a rim with a deeper profile. I was considering Deep-Vs until I ran across the Fusion which came highly recommended as an all-around rim. Not as light as the Open Pro but not as heavy as Deep-V. I should be able to build a reasonably light wheel that will be plenty Clyde-worthy without too much lateral flex. I'm also going from 4x to 3x on the 36H build which will save a tad of weight and increase lateral stiffness. If I do the 32H wheelset, I'll go 3x.

I talked to techs at Pro Wheelbuilders and at Velocity today and both of them said that for my style and level of riding, the weight advantage of the Revolution spokes would be negligible and neither thought that the increased elongation would make a significant difference. With my size and riding conditions, it sounds like a higher tension is more important that spoke diameter and the Fusions have a significantly higher manufacturer recommended max tension (125) than the Open Pros (95). The guy at Pro Wheelbuilders said I could even go a smidge higher on the DS and wasn't concerned about the stress on the hub flange as long as I didn't get carried away. Right now I'm running about 115 on the DS (yeah, I know, over Mfg rec).

FB, if you're still checking on this thread, can you tell me more about the advantage of using lighter NDS spokes.

OK, but we have to start with an understanding of the role tension plays. We don't use tension to make wheels stiffer or stronger because it doesn't affect those. We use higher tension to stretch spokes more.

This is important because a spoke is only a structural element while it's under tension and looses tension whenever the rim is deflected in its direction. The more a spoke is stretched, the more rim deflection it can take while still being under tension.

Once you focus on elongation vs tension you get a clearer picture, and realize that thinner spokes can do their jobs at lower tensions than thicker ones. So, while thicker spokes build a stiffer wheel, thinner ones make one that can work at lower tension.

Now look at a dished rear wheel. There's a tension differential proportional to the difference in the right and left CTF distances. So, we are dealing with tension variance of almost 2:1, and a working range bounded by what the rim can take, and a minimum needed to cover normal (and abnormal) tension losses to deflection. Using a lighter spoke on the left, lowers that minimum, and makes it easier for both to fall within a target tension range.

OK, thanks, that makes sense and sounds like it may help with the issue I've been having with NDS nipples working themselves loose on rough roads despite the use of R&R Nipple Cream during assembly. I'm hoping that the Fusion rims will reduce the problem by allowing higher overall tension, but perhaps running the Revolutions on the NDS would provide some added insurance. Any downside to using different diameter spokes on the NDS and DS?

First of all, if there were downsides to lighter spokes on the left, that I thought material, I would have told you. The only one is the loss of lateral rigidity, but since you were considering going to 1.5 all the way around, I figure that it's acceptable.

Meanwhile, I don't get why you think that using a teflon lubricant of spoke threads would somehow reduce their tendency to loosen. Nipple cream is OK, but exactly what you DON'T need if concerned with wheels loosening up in hard use. Switch to a stiff and sticky grease, which will provide good lubrication as you tighten the wheel, yet counter any tendency of nipples to spin loose.

lastly, you can get better advice from knowledgeable people on this forum, if you'd lay out the big picture up front, along with the problems you have, rather than asking for advice based on a partial story.

OP, have you considered an asymmetric rear rim to help with the tension balance? That combined with different gauge spokes will make for a very robust wheel.

Do you mean 'die', for cutting more threads on the spokes? That would make more sense (nipples are already tapped through) but would be a horrible idea for several reasons.

Thank you for your answers. They have given me additional insight and some possible solutions to consider.

I didn't start with a long-winded explanation of the related but separate projects because I initially had two specific questions, for which I received helpful answers. Consideration of the responses, which included suggestions such as your description of using two different spoke diameters on a rear wheel build, brought up additional questions which required the inclusion of additional information about the history and intentions of the project. Subsequent responses resulted in further evolution of the conversation.

Rock N Roll Nipple Cream is supposed to (according to the manufacturer) have properties similar to WheelSmith Spoke Prep in that it supposedly provides lubrication during assembly to reduce wind-up and then sets to a semi-solid to prevent loosening from vibration or tension cycling. The main difference is that the wheel is supposed to be laced up wet rather than allowing the product to set prior to assembly as with Spoke Prep.

As I'm sure you are aware, opinions on spoke preparation are diverse and some can be zealous. "Use a speck of grease", "Use a drop of oil", "Anti-seize is the way to go", "Boiled linseed oils is all you'll ever need", "Never build without Spoke Prep", "Spoke Prep is a crutch for builders who don't know what they're doing", "A good build doesn't need any lube or glue", "Use locking nipples on the NDS", "Use Spoke Freeze", "Oh hell no, don't use Spoke Freeze" ad infinitum.

In my first few wheel builds I used anti-seize compound on the advice of a local wheel builder. I have had no problems with any of my wheels until last summer with the rear wheel of a 700c 36H set with Open Pro rims, 105 hubs and DT Swiss Comp spokes. For some reason, possibly related to a flatting incident, the wheel developed a problem with the NDS spokes spanning the weld working themselves loose. The problem got progressively worse even though there is no visible damage to the rim, around the eyelets, or to the inside or outside weld. I tried increasing the overall tension, detensioning and replacing the offending spokes/nipples and retruing and tensioning, and eventually to rebuilding the wheel, cleaning off the spoke threads and reassembling using the Nipple Cream and new nipples.

The problem persists so I have decided to rebuild with a different rim.

I greatly appreciate the advice of the good people here and have also contacted a couple of other reputable wheel builders and manufacturers/suppliers.

Spoke threads are rolled, not cut.

Exactly, hence 'horrible idea.'