breaking Mac CN424 spokes

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WinterRider
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by WinterRider

pdlpsher1 wrote:
Tue Jul 16, 2019 8:00 pm
If a spoke breaks at the elbow it's due to movement there which causes fatigue. And the movement is caused by too low of a tension on the NDS. The low tension is dynamic and happens when you hit a bump on the road. Since you are very light I suspect 1) the geometry of the hub isn't ideal, 2) too few spokes, 3) too light of a spoke, and 4) the rim lacks the radial stiffness to transfer the load across many spokes. If you wish to keep the same hub and rim my only recommendation is to use a heavier spoke. The most efficient remedy with the least increase in total wheel weight is use more spokes. Hope this helps.
Disagree.

Less spokes NDS means higher tension each unit.. less to no slack instances. Root of the triplet success... 16/8

Then.. the lighter Laser is stretched more once tension-ed.. less likely to go slack. Think given the OP's weight those Lasers need to be 75 kgf or higher TIRE mounted. Tire pressure another factor.. less psi of course means less slack at impacts.

I did lace a 24H 12/6.. albeit w a Kinlin 300 rim at 450 grams. 2/1.8 Sapim's... 137/97 tension average DS to NDS. 2x and R left. Might be my stiffness personal set... albeit the rest are mostly Kinlin 200's.. one 270 rear.
Litespeed 2000 Appalachian 61 cm
Litespeed 1998 Blue Ridge 61cm

Fitness rider.. 2 yrs from seven decades age.

That is my story and I'm stick'n to it.

alcatraz
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by alcatraz

WinterRider wrote:
Wed Jul 24, 2019 10:51 pm
I did lace a 24H 12/6.. albeit w a Kinlin 300 rim at 450 grams. 2/1.8 Sapim's... 137/97 tension average DS to NDS. 2x and R left. Might be my stiffness personal set... albeit the rest are mostly Kinlin 200's.. one 270 rear.
That's interesting. I'm curious to try lacing a 12/6 myself (on carbon) after the success I had with 14/7. I was expecting to have to true the wheel but it's been bomb proof solid @21h going over terrible roads and potholes. The hub doesn't even have a triplet nds flange offset, and I don't even get brake rub which I sometimes got on my 24h 12:12 carbon build with the same hub geometry. Seeing as 24h hubs are available everywhere, maybe an 18h rear isn't completely out of the question. I think 3x:0x really makes the most of the few spokes that are there. Tensions are nearly 1:1 which feels good.

Before I went triplet 24h seemed to be the lower limit. Now 21h is more than enough for me. I wonder where the limit for triplet is (on carbon). :D

I'm not a pro wheelbuilder. I'm just reporting what I see.

by Weenie


bm0p700f
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by bm0p700f

The spoke failure is not caused by hub geometry leading to poor nds tension. The park guague under reads. I think this could be the overlooked reason here. If you have 1200n showing on that expect 1000n or less. but its worse though. The charts are not great. You actually have to create your own chart for each spoke to get that guage to work.

So the cause of the failure should be a poor low tension bulld. The problem is you did not know. So most of the advise above has neglected this simple fact. Nds heads in, is definitely a weekness. The hub has to be machined specifically for this to work. It isn't so don't do it. Replace 2x both sides. You can't do 3x with 24h as one poster suggested.

To give all those who think low tension nds is problem. Explain This then. 24 spoke rear wheel with a 1:1 lacing hub with 17/49mm flange spacing. Rim pacenti sl23. CX days used and tension balance of 34%. Ds tension 1200N then a tubeless tyre is fitted. Wheel is stable under my 86kg. Low nds tension is not the problem itis portrayed to be.

Op rebuild the wheel 2x both sides with new lasers or race spokes,either are fine. Calibrate your guage first though.

alcatraz
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by alcatraz

424s/cx-rays/1420s also probably aren't the goto spokes for alloy builds.

Maybe try to save the build by increasing tension, and if that doesn't work swap the spokes and/or go 0x:2x which would require new nds spokes anyway - inconvenient.

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WinterRider
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by WinterRider

bm0p700f wrote:
Fri Jul 26, 2019 12:21 am
The spoke failure is not caused by hub geometry leading to poor nds tension. The park guague under reads. I think this could be the overlooked reason here. If you have 1200n showing on that expect 1000n or less. but its worse though. The charts are not great. You actually have to create your own chart for each spoke to get that guage to work.

So the cause of the failure should be a poor low tension bulld. The problem is you did not know. So most of the advise above has neglected this simple fact. Nds heads in, is definitely a weekness. The hub has to be machined specifically for this to work. It isn't so don't do it. Replace 2x both sides. You can't do 3x with 24h as one poster suggested.

To give all those who think low tension nds is problem. Explain This then. 24 spoke rear wheel with a 1:1 lacing hub with 17/49mm flange spacing. Rim pacenti sl23. CX days used and tension balance of 34%. Ds tension 1200N then a tubeless tyre is fitted. Wheel is stable under my 86kg. Low nds tension is not the problem itis portrayed to be.

Op rebuild the wheel 2x both sides with new lasers or race spokes,either are fine. Calibrate your guage first though.

IMO you over stating the deficiency of the Park Tension meter. Some yes need calibration.. all brands of spoke meters can get reading off actual conditions. Mine has been spot when checked.. another key issue is how it's operated. Does take some consistency/technique in that regard too.

So.. your stating 34% of 1200 being ~40 kgf.. is sufficient to prevent elbow breakage w spokes apparently going slack w strong impacts?

Yet.. are we comparing apples to apples so to speak (?). Lacing patterns... tire pressures.. rim weights and stiffness...
all factor in. Elbow in relation to flange is another.. snug or close against flange helps... washers bring the head tighter obviously.

If.. your running those NDS's radial at ~40 kgf outbound the flange is interrupting the tension cycle of the spoke. Likely then their not slacking during the cycle.. which from memory amounts to about 1/50th of a second.

Actually forgot all the de-tales of the OP's wheel.... need to go back and reread it.
Litespeed 2000 Appalachian 61 cm
Litespeed 1998 Blue Ridge 61cm

Fitness rider.. 2 yrs from seven decades age.

That is my story and I'm stick'n to it.

bm0p700f
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by bm0p700f

You can have stable build with low nds tension is the wheel is radially and laterally stiff enough. High nds tension does confer some advantages so long as your not compromising on lateral stiffness.

edit as this was unfair.

I have built many wheels with poor tension balances. Not one has ever gone wrong. I must be getting something right.

Given the ops rim and spoke choice, the only reasonable explanation for the failures of spoke tension is not as even and as high as he/she thinks. insufficient stress relieving may also be a factor. Tyre choice does not come into this. A wheel should be stable regardless of the tyre fitted or it not a good build.
Last edited by bm0p700f on Fri Jul 26, 2019 11:34 pm, edited 1 time in total.

bm0p700f
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by bm0p700f

The bites hub dies not need spoke hole washers. In the thousands of wheels I have built I have never used washers and spoke failure can be counted on one hand. So this again is one of those myths that need beginning. If you get the stress relieving right and the tension even with around 1200n DS (with modern rims) with a build that has sufficient lateral stiffness to avoid the nds spokes going slack (and sufficient radial stiffness to avoid the same) then there is no reason why spokes would fail. Can spokes are unknown to me through. I have no idea how reliable they are but I assume they are reasonable.

bm0p700f
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by bm0p700f

alcatraz wrote:
Fri Jul 26, 2019 2:31 am
424s/cx-rays/1420s also probably aren't the goto spokes for alloy builds.

Maybe try to save the build by increasing tension, and if that doesn't work swap the spokes and/or go 0x:2x which would require new nds spokes anyway - inconvenient.
Spoke have failed therefore they are fatigues so all spokes should be replaced.

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WinterRider
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by WinterRider

bm0p700f wrote:
Fri Jul 26, 2019 8:05 am
You can have stable build with low nds tension is the wheel is radially and laterally stiff enough. High nds tension does confer some advantages so long as your not compromising on lateral stiffness.

I have explained this too many times and winter rider you still seem to not understand.

I have built many wheels with poor tension balances. Not one has ever gone wrong. I must be getting something right.

Given the ops rim and spoke choice, the only reasonable explanation for the failures of spoke tension is not as even and as high as he/she thinks. insufficient stress relieving may also be a factor. Tyre choice does not come into this. A wheel should be stable regardless of the tyre fitted or it not a good build.
Agreed.. yet again. :unbelievable:

Yet the nuisances.. which can/will mitigate issues.. WHEN wheels are built by someone not doing so daily.

Stress relieving.. :thumbup: ---> Primary importance.

*****************
The Quill is our most innovative road rim to date. Utilizing design technology from our Aileron disc rim, we’ve evolved our most successful and proven A23 road rim and developed the Quill to be, stiffer, and wider than its predecessor.

The Quill rim is 17.2% wider internally, 26.2% laterally stiffer, and 99.3% radially stiffer than the A23.* Featuring an outer width of 24.5mm and an internal width of 21.1mm, the Quill’s voluminous width provides riders with substantial lateral stiffness even in lower spoke counts and increased ride quality and control. The 25.5mm depth, provides an aero profile giving it significant performance and durability gains over previous rim brake models. The Quill can easily be set up tubeless with the use of our 21mm wide Velotape.

Tight tolerances require the use of a low profile rim tape like Velotape to avoid tire installation issues. Veloplugs are not recommended on Quill rims.

*Stiffness Comparison Formula = [((1/(Quill Displacement)-1/(A23 Displacement)))⁄(1/(A23 Displacement))]

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OP's rim specs

Specs
RIM SIZE: 700c

WIDTH: 24.5mm

HEIGHT: 25.5mm

OPTIMAL TIRE WIDTH: 25mm - 47mm

TIRE INTERFACE: Clincher / Tubeless

VALVE: Presta 32 - 40mm

BEAD SEAT DIAMETER (BSD): 622

EFFECTIVE RIM DIAMETER (ERD): 589

WEIGHT: 465g

MACHINED SIDEWALL DRILLINGS/COLORS:
Litespeed 2000 Appalachian 61 cm
Litespeed 1998 Blue Ridge 61cm

Fitness rider.. 2 yrs from seven decades age.

That is my story and I'm stick'n to it.

JoO
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Joined: Thu May 04, 2017 7:30 am

by JoO

I am still on the fence what to do with this wheelset.
Now I use my set with kinlin XR22 (ofsett rim).
Very stiff and light set but I like the quills better (more tire volume due to 622-21)

Or I change all the NDS spokes and up the tensions. (perhaps make a DIY calibration tool using a scale)

Or I change to a 2:1 spoke pattern. Could I use a 32 hole hub for this or does it require a specific 2:1 hubset?

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F45
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by F45

Calibrate your Park meter because at high tensions I've found them to be off so the real tension is lower than you think it is. Then you add a tire and it's even lower. I also use 424s on my mountain bike wheel builds and I've never had a problem in years of use.

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