Sapim Strong (single butt) versus DT Alpine 3 (tripple butt) - "most failure proof"?- Mtbr.com
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  1. #1
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    Sapim Strong (single butt) versus DT Alpine 3 (tripple butt) - "most failure proof"?

    I'm finally building my 29+ and 26fat wheels for my BigFatDummy. I use it as a car-replacement, as well as trail building and bikepacking with the kids. It sees ~400lb total weight often enough (and ~330lb quite frequently, on trails) that my main (sole) concern is durability of the build.

    Despite reading the top ~50 google & mtbr resultsin, I have questions ....

    FYI, for rims - after a lot of research I've gone:
    - DT bigride hubs all around. Brass nips obviously.
    - wtb KOM Tough (29+, an improved scraper rim) and blizzerk90 (profile seems likely stronger than other options ... was frustrating to choose this one, but it's done now )

    But I need to choose spokes. I'm mainly considering (but definitely open to other suggestions):
    • sapim strong (single butt 2.3/2.0)
    • dt alpine 3 (tripple butt 2.3/1.8/2.0)


    In order of things I care about:
    1. reduce risk of catastrophic failure (taco, etc), especially after considerable use (I do check spoke tension, but hope to use the wheel for a while)
    2. reduce risk of wearing them out (spoke failure (eg, at j-bend) rim nipple bed cracks, etc)
    3. weight and/or cost ... way down the list after the above


    I've read The Bicycle Wheel, sheldon brown, and what feels like the entire internet, and have a mechanical engineering background (hehe this might be the _source_ of my problem here ), but this space seems to have some frustrating missing pieces of detailed public analysis, as well as a metric Sh!tTon of dogmattic responses

    So - what is your take on which spokes in my build will give me the best long-term highest safety margin and durable wheel?

    Thank you!!

  2. #2
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    a few thoughts RE various sources online that you may have read. No particular order.

    failure modes:
    • catastrophic failure: a "taco". I have found zero detailed analysis of whether a taco is one mode or many, specifically. Like, does a taco only result from a side load pushing the rim out of true enough that the taco occurs, or do other/combinations cause some other failure first (like broken spoke or radial deformation, then followed by the axial deformation that is the taco)
    • spoke failure at j-bend. Typically not catastrophic, but could cause the wheel to be trash due to the higher loads elsewhere after the break)
    • or nipple bed cracking, which is obvoiusly a good sign to trash the rim (it's Aluminum) even if it were hypothetically repairable.


    strength versus durability:
    • people seem to use this interchangeable (which is wrong) for referring to stiffness (deflection per load) or ultimate strength and/or possibly fatigue life in the system.
    • I see at least three viable design aspects I should care about for my critera - but no answers on the web detailed enough for me to feel good about the answer. To be fair, it is a rather complex system, and of course the foremost aspect is simply the quality of the build itself
      • the thinner cross section of the the butted spoke leads to a higher total elongation needed to initially tension the wheel - so for a given deflection induced during use, the spoke unloads (decreases tension) LESS. This helps both maintain nipple pressure (less likely to unscrew) and increases fatigue cycles to failure (all other things equal)
      • the thinner spoke will stretch/deflect more for a given load vs a 2.0 cross section. Since other parts of the build (namely rim) do take at least some load, the implies (I think convincingly?) that a given load on the _wheelset_ will result in slightly lower peak loads on any given spoke (more distributed among several spokes). This is great for fatigue life if true.
      • the thicker spoke's higher stiffness means a given load may impart less overall deflection to the wheel. I am inclined to believe this tradeoff follows from the above. This seems to have implications for keeping the system alligned, which is obviously critical to avoid failure. Radial seems like a mixed bag (reduction in deflection comes at expense of higher peak stresses). Axially (side-to-side) though, this could keep the rim more true, which seems plausible to have an important effect.
    • so with catastrophic failure by far my most important concern, does this reduced side-to-side deflection (thicker or straight spokes) swamp the fatigue improvements from the butted?


    data points based on some specific race team practices:
    • Absent really detailed responses from the teams (which I have never seen) I REALLY don't think this is valid. The race team has drastically different requirements than mine.
    • they replace equipment frequently, so they may never get it to the same cycle lives
    • they likely care about weight, stiffness, and power transfer in ways that differ from my reqs
    • their disciplines (from the examples I've seen, namely races on road/cobble or DH/enduro) are different than mine, eg different equipment: fat rims and/or suspension.


    double-vs-triple butted.
    • most spoke failures are at the j-bend (or the threads ... but tripple and double butt are identical there)
    • so triple butted (2.3/1.8/2.0) seems clearly superior for MY USE than double 2.0/1.8/2.0) .. .only possible downside is cost, weight is much closer than straight-vs-double

  3. #3
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    https://www.wheelfanatyk.com/blog/for-spoke-nerds-only/

    an interesting, albeit anecdotal, quote from a well-known individual with spoke-manufacturing experience
    "Alpine, DH and Strong spoke models. 2.3mm x 2.0mm m[...] virtually eliminate spoke breakage. Rather than transferring the failure to the thread, in practice they seem to transfer it to the hub (flange crack), rim (hole crack), or time (eventual mishap)."

    Eg, the weak point of the wheel is typically the spoke elbow, but when that problem is fixed, the next week point is the rim or hub flange. Going from _straight_ 2.0 to the single butt would seem to affect hub/rim as follows:
    • A wider j-bend would have more contact with the flange, meaning it could _reduce_ flange failures (eg, benefit that part of the system; even if that is next to fail)
    • rim-wise, the spoke behavior would seem to be nearly identical to a straight spoke - so no effect either way on rim failure.



    What this unfortunately doesn't comment on - what effect would reducing the spoke stiffness (going to 2.3/1.8/2.0) have? Does this benefit rim failure at all?

  4. #4
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    Is your 400lb weight from towing a trailer, or is the bike physically weighed down with 400lb?

    Basically, you're building tandem wheels. Sort of. I'd use 36 2.0/1.8 common spokes, and if you bust one every few years, it's not a big deal.

  5. #5
    turtles make me hot
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    From a scientific standpoint, I can't add much. I've been a mechanic for most of my life and have been building wheels for about ten years.
    When I first started building wheels for myself, it was out of necessity and the feeling that I was certainly capable of doing a better job than most of the crap commercially available. The first set of wheels I built for myself had 36 straight gauge spokes. They were awful and I hated them. I replaced them with similar rims with 32 double butted spokes and liked them a lot better. This was on a full suspension 29er.
    I since started building lots and lots of fat and plus wheels. I weigh about 275 (maybe more, I'm afraid to look) and I no longer destroy wheels ever. I even use aluminum nipples on my wheels now, which I never would before. I probably wouldn't build myself a 30mm rear wheel for a hardtail with aluminum nipples and 2.2" tire.
    I have found that fat and plus tires are incredibly forgiving and offer a high degree of protection to rims and nipples. I want a BF Dummy also and really never gave any thought to spokes beyond I'll probably just use DB Sapim Race like I use on just about anything.
    I would pick the DT Swiss spokes. Just because.

    What tires are you thinking about using?
    I like turtles

  6. #6
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    Quote Originally Posted by One Pivot View Post
    Is your 400lb weight from towing a trailer, or is the bike physically weighed down with 400lb?

    Basically, you're building tandem wheels. Sort of. I'd use 36 2.0/1.8 common spokes, and if you bust one every few years, it's not a big deal.
    Yep, basically a tandem. The BFD is a longtail, 15x150mm/12x197mm fatbike.

    I tried for some time to do 36h. The problem is mainly hub choice (the ONLY option i found was having onyx custom drill one; total cost ~$600, front AND rear if i wanted to do it right because it's impossible to unload the front wheel over impacts, due to the long-tail). Rim choice is also much more really limited. So, 32h it is.

  7. #7
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    Quote Originally Posted by NYrr496 View Post
    What tires are you thinking about using?
    Good points on tire & being more forgiving ... I"m actually banking on that somewhat

    I use maxis minions for the most part; I end up on 50/50 pavement/hardpack today (one wheelset for everything) and the center tread of these is a nice balance. I have snowshoe2xl's and studded snowshoeXL's to try on the blizzerk90's for winter with the new dedicated wheelset, and haven't settled on a 29+ tire yet.

  8. #8
    turtles make me hot
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    I wish Surly made the Extraterrestrial in 3" for pavement use.

    I really like Bontrager's XR2, XR3 and XR4 and the Vee Bulldozer.

    29x3" Knards on pavement only. I hate them as a front tire on trails.
    I like turtles

  9. #9
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    Sapim Strong have been great on my downhill bike (200lb rider that hits 40mph almost every time I go).
    I like bikes

  10. #10
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    Bump, hoping someone has some meaningful data.

    My assumptions are, to summarize my OP, that the tradeoff is overall stiffness of the 2.0mm spoke main section (especially axially / side-to-side), versus the less stiff / load distribution (assuming this is true) of the 1.8mm spoke.

    I am sure many folks think this is question is irrelevant ... but consider among other things: for a given load, the 1.8mm spoke will elongate 20 percent more than the 2.0mm spoke. This seems plenty significant of have a real effect, especially knowing that the thicker 2.34mm J-bend of these spokes is effectively eliminates spoke failure at the flange.

  11. #11
    turtles make me hot
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    I'm also curious if someone more in the know would use different spokes for 26 and 29 inch wheels on the same bike?
    I like turtles

  12. #12
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    Quote Originally Posted by NYrr496 View Post
    I wish Surly made the Extraterrestrial in 3" for pavement use.

    I really like Bontrager's XR2, XR3 and XR4 and the Vee Bulldozer.

    29x3" Knards on pavement only. I hate them as a front tire on trails.
    I run Bontrager Chupacabra 3" front (also like XR2/3/4's) and a 120 tpi Knard on all surfaces and like the Chupa better.
    【ツ】 eDub 【ツ】

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