SortaGrey

NDS spoke durability is my last issue per trying to learn some things about wheelbuilding this winter. I've read & been patiently tutored about the use of brass washers.. different lacing patterns including radial.. butted spokes.. offset rims.. glueing the NDS spokes to prevent them going slack... about have covered the gamet. Still some issues leave questions.. against this backdrop. I set something over two big stones (200+ lbs currently) on my rear wheel. Once in a while one is forced to take a pothole... sure we all try to avoid them but it does happen. Say at 17mph... bang.. that rear takes one heck of a jolt. Usually that event does not break spokes.. hasn't for me at least... I'm riding a good LBS 36H build. But that jolt sets the stage for a break/s later on. That spoke stressed.. fractured [?].. goes later. Head slap I'd term it.. the detensioning of the spoke and rapid retensioning as the wheel rotates... usually they go in the elbow area. Yet it looks to me like any method used does not prevent this 'head slap'.. some numbers.

This data comes from a 46mm hole width flange.. 33.1 vs 20.7 flange center.. 72/113-116 KgF build.. later figures vary with lacing.. not really that significant. Using these spoke options: 2.3/12 gauge, 2.0, 1.8 and 1.6mm's.

1.6's show .020" elongation under tension at 3x.. .0208 at 4x
1.8 .016 3x .0165 4x
2.0 .013 3x .0133 4x
2.3 .009 3x .0101 4x

Any of these spoke options is going to completely detension via said pothole scenario.. I wonder if in every case the spoke head is going to set back into that recess the same way? The elbow bend is getting a jolt no matter the spoke diameter.. washers I guess would set that impact in way to lessen the bend stresses [?]. Washers in effect try to accomplish the manner in which straight pull spokes function. Butted stretch they say more in the middle.. lessening impact on the bend... that I question. Given the short timeframe.. and still the bend gets a rap.

Improving the spoke line/angle to the flange on the inside spokes... an attempt to get flange contact after the bend. Is this really a pre-stressing of the spoke... giving the metal some.. the word (?).. some memory.. or ability to handle later stresses of this type?

My inquiry is a desire to understand why something works.. or doesn't. Testimonials aside.. the why's.... Spokes will continue to break.. one of my motivations is when I come across the heavy wt spoke buster.. I can be of some real help.

12 gauge on the NDS.. I threw that out per the relative mass of the metal. If their practical NDS I doubt it.. but I wonder given their stiffness even at NDS tension levels. 48H is the answer for these applications.. yet find the hubs of decent [?] quality that'll fit traditional rear dropouts.... sans a tandem.

BCRider

I think you're over analyzing the situation. Where the spokes tend to break isn't from hitting the potholes. It's from inadequite tension working at the spokes to detension them on every revolution. Bend a piece of metal a few times and it's fine and still strong. Bend it the same way a few times per second and it doesn't take long to build up enough fatigue to make it fracture and snap. Your pothole worry is one of the "a few times" scenarios whereas the loose spokes are the "few times per second" example. There's also no lack of 200lb+ riders that are hammering their wheels doing big drops on trails and urban settings and the wheels last a decently long time when built properly. I doubt if your potholes add up to that same sort of punishment. And don't underestimate the cushioning effect of the tire and air pressure. If the tube doesn't pinch flat from the pothole strike then the rim and spokes did not receive a seriously crushing blow to a single spot. The tire and air pressure spreads out the impact over at least a few spokes in that area.

dabac

The No.1 spoke killer is well established to be fatigue, not sudden jolts.
A jolt might be the thing that kills off a spoke well on its way to fatiguing, but isn't the initial source of the problem. That spoke would have gone a few days/weeks later anyhow.
And at the elbow is where it usually happens. Once in a while one will snap at the onset of the threads, but the majority happens at the elbow.
Using threadlock prevents nipples from unscrewing, but to make unscrewing a reality the spoke has to slack first.
But the key priority in a good build is to have sufficient tension as to prevent spokes from ever going slack. Thinner spokes on NDS helps with this, as they allow you to build a wheel where the strain (load WRT surface area) can be more equally balanced despite the tension in absolute terms being different.
The strain is what decides the "stretchiness" of the spokes, and a higher strain means that the load cycling will be less as the wheel rotates. Helps keep the spokes under tension.
If the "normal" fixes,(different gauges, offset rims, NDS radial heads-out) doesn't work, then you might want to look into wheels with "paired" spokes, ie double the spoke number on the DS as on the NDS.
Another option (for a steel frame bike) is to re-dish the wheel to a more symmetric spoke angle, and then to cold set the rear triangles with an offset to compensate and make the wheels track again. You'll have to adjust the dropouts as well, watch out for crank/heel strike on chain stay, but is otherwise pretty much a non issue.

triplebutted

Do you have Brandt's book? I really like the science and theory about wheels in that book. Good read if you don't have it.

SortaGrey

I went thru Brandt.. when by me mostly. Learned more here and elsewhere on the net.. but I intend to revisit it.

BCRider you may well be right per over analysing it. Just I have the time now to get it hashed out in my noddle.. such as they is.

Dabac so noted per the jolts... metal fatigue yes. I've went to 130mm rear... wider yet means chging out the BB for the chainline it seems. I didn't cold set.. I spread when I chg out. I might go back to 5 sp on that bike at 126.... if I can get/find the custom 5 FW I want.

For sure.. rim stiffness figures into that jolt scenario.. how much deflection actually occurs. The inflated tire a good protector no doubt too... yet that limp spoke/s gets a workout.

I'll check to NDS going loose with use.. I've only experienced that in older factory wheels sans attention. It's amazing to me in retrospect how much those old wheels took before they started to break.. looseness etc. The bike wheel is indeed a strong unit.

My backup rear winter rider wheel I built the opposite way.. all the dish angle I could get. Say 50 some % of DS tension... that'll be my experiment wheel to add tweaks per maintaining said tension and how that chg's with time... and what is a good minimun NDS tension.

Narrow-er flange diameter means more spacer left using traditional widths in the rear. Hence closer tension between the two sides. Has any manufacturer past or present went that direction.. minimizing width to increase NDS tension? What's considered a minimun width for a flange.. any ideas?

fietsbob

Maintain wheel by occasionally truing , works for me.

Drew Eckhardt 

Spokes work when they're at sufficiently high tension without residual stress.

Spokes fail due to fatigue in too few cycles because of high average stress (not all of the elbow was taken past its elastic limit when the spoke was formed) solved by stress relieving and/or high variation (as from spokes going slack and bending back and forth like you'd do to break a paper clip when they have too little tension) which you avoid by keeping everything uniformly tight with corrected spoke lines.

Thinner spokes will keep the rim supported horizontally over bigger bumps than thicker ones because they have more stretch at a given tension so the rim needs to bend farther before they go slack.

1.8mm elbows are tough enough - Jobst Brandt has over 200,000 miles on a set of 1.8/1.6mm spokes ridden all over including dirt roads and cobblestones and he's not a small guy.

However, with large hub holes (to make insertion easy) and/or not enough of an obtuse angle on the end of the spoke you get high stress where the spoke bends until it's supported and leaves stress which cannot be removed thus leading to premature spoke failures on that wheel until larger spokes are used.

Buying just a single 1.8/1.6 spoke is also hard - few shops stock them because QBP doesn't sell them.

2.0/1.5 spokes work too, but some people have issues with windup and tension + too much torsional stress can combine to break them when building. Torsional rigidity is 23% less than a 1.8/1.6 gauge spoke 52% less than a 2.0/1.8. I put tape flags on representative spokes (drive side, non-drive-side) to see how much wind-up I need to undo and haven't had problems when I lubricate the threads with anti-seize even when re-using 12-14 year old alloy nipples.

1.8/1.5 have less windup to deal with because the smaller thread diameter imparts less torque on the spoke when it's being tensioned.

Drew Eckhardt 

Correctly built wheels don't need truing until their rims get bent or need replacement due to worn brake tracks. My last front wheel went 12-14 years before that happened.

SortaGrey

Corrected spoke lines... you mean bending the line down past the flange... ? I didin't grip that issue well when I read it in the book.. or online. Or.. making sure the line heads directly to the rim hole.. ie, not really a pre-stressing of the elbow bend?

200K on a set of spokes... I hadn't heard that. Makes me wonder about the rim.. and hub too... that's 4K a yr for 50 yrs......... must have been a good lot # of steel.

My point.. per the spoke elongation.. was the lighter gauge spokes get slack too.. under heavy rim deflection. Accepted they act as a shock absorber for the elbow.. but I'm still stuck on the jolt they receive when retensioned.. as the wheel turns. And the butted can still work loose... after that slack period like any other spoke... not set in place with some glue etc.

Definitely wire quality and the quality of the extrusion dies & drawing technique affect spoke quality. But like everything today.. what is real value... and what is just more advertizing wind.

Don't let them get loose.. improve the angle.. check.

dabac

Good minimum tension is whatever it takes to keep the NDS spokes seeing as little cyclic change in loading as possible - while not risking rim integrity or upsetting axle centering. The rest is all up to what kind of life you expect from the wheel.

Yes. Shimano XT disc brake hubs for instance has real narrow fnage spacing and surprisingly even spoke tensions.

Drew Eckhardt 

You push the outbound spokes inward with your thumbs so they follow the flange better and squeeze crossing spokes together near the rim so spokes leave the nipples at the correct angle instead of being bowed.

You replace the rims when they wear out and leave the rest of the wheel alone.

Well lubricated wheel bearings seem to last pretty much indefinitely, balls and cones are replaceable if that doesn't work out, and Campagnolo cups are sold as replacement parts.

If the rim can bend that far without damage.

When built with sufficient tension (whatever the Jobst method produces or a measured 110kgf on the drive side, and whatever the NDS ends up at with the wheel dished correctly) the spokes don't loosen until you hit something hard enough to put a permanent flat spot or bend in the rim.

Even with Campagnolo wheels which have a greater tension imbalance due to the longer freehub.

Even with nipple threads and sockets properly lubricated.

operator

Nipples don't work loose if you've selected the correct rim, hub and spokes for your application and that the wheel has been built with everything that makes a wheelbuild durable.

1) Strees relieving
2) Spoke tension as close as possible to the average on each side

spike420211

a different type of thread 4 spoke nipples:

https://www.spiralock.com/technology

Helps if u know of a good swiss machine shop

FBinNY 

A common error in wheel building discussions is to use the terms tension and stress interchangeably. Tension is the absolute load on the spoke, as in 100#s tension is equal to hanging 100#s on the end of a spoke. Stress is a bit different, it's the tension divided by cross-sectional area. It's an important difference because it's stress, not tension that defines the loading on the spokes, and whether they're in their in their optimum elastic range.

Besides offset drilled rims and other ways to equalize tension on both sides of the wheel, the best way to compensate for the unequal tension dished wheels need is to reduce the cross section of left side spokes. That allows you to equalize the stress of the left and right side spokes, while maintaining unequal tension.

Keeping the left side stressed (loaded) eliminates possibility of nipples backing off because a spoke goes slack.

Al1943

Stress is a force acting on a body and can be compressional, tensional, or shearing.

FBinNY 

Yes, and no. Stress is the force per unit area. It can be in compression or tension, but it's to force the way that pressure is to weight.

Since we're speaking of spokes, I assumed I didn't have to mention compression stress, my point being the difference between tension and stress.

JohnDThompson 

You can save yourself a lot of grief in the long run by avoiding vanity lacings like radial in the first place.

SortaGrey

I admit I liked the idea of radial on the NDS in order to keep continual tension on the spokes. But after more experienced advice I see it as a risky lacing. I go back to a picture I saw posted here back when.. the lead rider in a sizeable pack of riders in the process of going down via the collaspe of the front rim. NOT saying it was radial laced.. but from my view the first priority building a rim is durability. I cringe to think of riding a wheel that goes south.. I easily can think of so many scenario's where I ride that if that happened it'd be hurst time.

"the best way to compensate for the unequal tension dished wheels need is to reduce the cross section of left side spokes. That allows you to equalize the stress of the left and right side spokes, while maintaining unequal tension" writes FB.

Apologies for my being slow to understand.. you mean minimizing the dish angle with all the spacing you can use NDS?

I like the idea of using an XT disc rear hub to equalize tensions.... I'll have to look at those figures.

I'd sure agree a well built wheel should stand.. spokes should mostly stay put. I read all this breakage et al across the net.. my only real problems have been with a factory replacement wheel.. which teaches one quickly NOT to buy just to get riding.

I see the jolt scenario now as something I've placed too much emphasis on. I think of the narrow lite rims I see on a relative's bike.. one I haven't riden. That has kept me off that type of rim and tire configuartion.. the idea of doing the pothole I ran thru last fall.. which didn't phaze my rider rim at all. I figured that event led to the inbound NDS broke spoke early winter... near of bend per usual. Likely just fatigue.

FBinNY 

Using different spoke gauges does nothing to change dish, it's a way of adapting to the problem of unequal tension dish imposes. the amount of dish is controlled by the hub flange asymmetry, and the rim asymmetry (if any) since the rim needs to be centered between the axle faces.

The right flange distance from center is as far as possible leaving room for the cassette. Moving the left flange in helps reduce dish, but experience shows that going far enough to have symmetry reduces the side strength of the wheel so there's a bit of a balancing act between symmetry and side strength.

Once you realize that there will be dish and therefore unequal spoke tension, the question is what are the problems that unequal tension creates. The main one is that you often face a choice of excess tension on the right or inadequate tension on the left, or some kind of compromise between them. On the left side the inadequate tension means that the spokes aren't stretched enough to stay within the elastic range as the wheel flexes. A thinner spoke will be stretched more than a thicker one at the same tension, so by using lighter spokes on the left you can avoid the undertension common on left spokes of highly dished wheels.

BTW- I agree with John T. - you should stick with the basics with your first builds. It's best to learn to crawl before you try walking or worse yet running. As you build skill and confidence, you can experiment knowledgeably in the future.

blamp28

+1. Start with just building. You might like to try off center spoke hole drillings like Velocity Aerohead OC or Synergy. There are others as well. By offsetting the spoke bed a bit closer to the NDS, the dish is slightly reduced. YMMV

fietsbob

don't have to stick with stock specs.
Spreading the rear axle width, lets the hub move to the center line,
so the flanges are equidistant to the center line, and then dishless wheels can be built
140, 145, wide axles are common to tandems.. Shimano's hubs for tandems share 10x1 axle spec ,
so you can modify frame and hub to suit a heavy rider application.

CoMo uses this change on their single touring bikes too..

SortaGrey

I ran the data I could find on the Shimano disc rear... #755. Comes out around a 75/115 KgF build.. similar to the FW hub I did recently.

Using the OC Aero rim.. moving the center 4mm left.. the tension goes 100/115.

The difference in elongation... stretch.. between 1.8's and 2.0 spokes at 75 KgF is 3 thousandth's of an ich.. .003. This data from the WheelCalc program. 2.0 vs 1.6 the difference is .007"

Roughly figuring.. to build a symetrical rear with 130 spacing.. you'd need a flange width of around 1.5"... 38 mm.

BCRider

Sortagrey, you should realize by now that the rear wheel is a compromise due to the dishing needed by the gearing. Having said that literally many millions of less than perfect machine built wheels roll around every year hauling folks that are both small and large. They do this with little attention from their blissfully unknowledgable owners until sometimes a spoke snaps. They'll often ride the bike with the broken spoke for a while before doing anything about it. So a spoke or two breaking isn't generally going to cause a full on wheel collapse instantly. Especially if you stick to higher spoke count wheels.

So while all you've written about is actually going on in a wheel it's not anything that you need to lose sleep over. Build your wheels using some care to tension, stress relieve and true them well and they'll be fine. For your first builds stick with 32 spoke designs using the tried and true 3x pattern on all sides. If you build them decently and reach the sort of tension ranges needed on the DS and NDS you'll find that you need little or no re-truing for many years. But since they are your first builds and we are all just human it would be wise to keep an eye on them by inspecting the tension and trueness reasonably frequently for the first few hundred kms.

Is the use of fairly extreme dishing such as we see on modern 9 and 10 speed rear wheels a good thing? No, it obviously has a lot of compromise involved to make room for that many gears. But while there is a compromise that affects the spokes it's equally true that many hundreds of thousands of wheels that are out there carrying the latest ultrawide 10 speed (and now 11?) cassetes are surviving just fine despite potholes and other road hazards. Hence my suggestion above that you're overthinking the issue.

Many things come together to result in a wheel collapsing like you saw in that picture. And often they all have to happen at the same time. The odds of that are slim but if it does happen it won't be due to any sort of failure from hitting potholes which loosens and jams the spoke heads in a decently built wheel.

blamp28

I'm not understanding what you are trying to accomplish here. I am a heavy rider and ride the Shimano Disc hubs on my MTB and Tandem builds. these bike both operate at an extreme as far as spoke durability goes. The Tandem carries a 425 lb team plus packs and accessories on 50+ mile rides every weekend. The MTB is used only off road for xc racing on trails with plenty of technical features. There have been no issues whatsoever to give me concern for the NDS spokes on either bike. I have never needed to make even the smallest adjustment. I just ride them.

SortaGrey

I'm trying to get all the ideas/input I can per building issues I'm currently working with.. that simple. Mileage varies.. ie, someone's experience and testimonials are just their own in the end. I've read and listened to a good deal of contradicting info this winter gathering build techniques. As always opines vary... as with anything.

I don't believe the butted spoke is worth the coins.. given the slight increases in stretch.. given decent tension. Some granted see it differently.

I guess one of my main motivations is a younger (way heavywt) guy I found on a ride with a rear otta wack via broken spokes. His attempt to 'get back into shape'... I later learned derailed after spoke frustrations. Now I'd be glad to offer help if this scenario comes along again.. wanting to have all my ducks in a row so to speak.. on how to maximize the durability of a rear build. So in the end I'm attempting to get it all down this snow season.

Must be.. some width flange minimum per a rear vs stability issues. Why not a 38mm flamnge width 130 spaced rear... for a symetrical build? Likely not stiff enough laterally...