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  1. #51
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    Quote Originally Posted by meltingfeather View Post
    If you ignore almost every other post in the thread, including my measurements and data reporting that started it.

    "It depends" is about as good as you can get looking at my original results vs. yours (and his).
    Your categorical proclamation that tire pressure is responsible is... how u say... wrong.
    If you have a wheel and you change the air pressure in the tire and the spoke tension changes
    then meltingfeather I ask you, what other force is responsible for the change in spoke tension?

    please... get some books on physics and learn how a wheel/tire actually works

    unlike you, who says sorry you are "wrong", with no further explanation

    I provided simple clear "facts" to back up that statement
    if you don't like that bad luck, this is to for the other intelligent forum readers...

  2. #52
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    Tire Pressure and Spoke Tension

    Quote Originally Posted by InertiaMan View Post
    Seriously? Apparently it is YOU that hasn't read the thread. I posted extensive data one day after you asked for it.
    I probably saw your "don't have original data" post in an email update and didn't look back for follow up "unoriginal" data... Understandable I think, now that I'm familiarizing myself with year-old dialogue again.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  3. #53
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    [QUOTE=Muchas;11119813]
    Quote Originally Posted by InertiaMan View Post
    :


    I'm really interested in this thread - brilliant!. I'm surprised to see the de tensioning with the LB wide carbon rims!, I've just had them laced up and they came back in my opinion with pretty slack spoke tensions, I don't have a tension meter but comparing them with my other mountain bike wheelsets they would appear to have half the tension!. The Maxxis HRII tyres were very tight to get on and believe that the tight beads are indeed playing their part in the tension of the spokes. I think I will retension the spokes with the tyres on and see how they perform.
    (650B 35mm wide rim)

    Thanks guys
    from my observation, more internal rim width will increase on the amount of spoke de-tensioning from tire air pressure, due to increase of the area of the rim the air pressure is acting on

    what I also found is that after tire de-inflation you are left with the bead pressure
    measurable on the spoke tension gauge, immediately after you unseat the bead the spoke tension drops back to initial

    unseating the bead on the Enve 26Am rim dropped the spoke tensions by about 10kgf/spoke
    hard to believe it would be this high a value, as it was not hard to do (unseated the bead by hand)

    as you pump tire pressure you will overcome this bead pressure as the outer tire also pulls the bead away from the rim

  4. #54
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    Tire Pressure and Spoke Tension

    Quote Originally Posted by WaXed64 View Post
    If you have a wheel and you change the air pressure in the tire and the spoke tension changes
    then meltingfeather I ask you, what other force is responsible for the change in spoke tension?

    please... get some books on physics and learn how a wheel/tire actually works

    unlike you, who says sorry you are "wrong", with no further explanation

    I provided simple clear "facts" to back up that statement
    if you don't like that bad luck, this is to for the other intelligent forum readers...
    It's unfortunate that you bring infantile emotional rhetoric to a mostly valuable thread. Clean up your diaper and regroup.
    Limiting the discussion to the relevant (this thread) context so we can all easily be on the same page, I did not say that pressure does not contribute.
    I can not ignore the fact that the data demonstrated that it did not in my case; if you'd like to take that up analyze my measurements to support your position.
    I said you are wrong because my results and numerous others clearly show you are. Pressure is not the sole responsible mechanism as you proclaimed.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  5. #55
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    Tire Pressure and Spoke Tension

    Quote Originally Posted by InertiaMan View Post
    Finding the origin of quotes is easy: just click on the little blue double arrow at the top of the quote, and it will take you there.
    Thanks for the tip, coach. It doesn't make out of context cherry picks any more relevant.

    Quote Originally Posted by InertiaMan View Post
    I'm hardly drawing on "the whole of your post record" or taking you out of context.
    Sorry to point out the painfully obvious, but grabbing a single sentence from another thread/conversation and bringing it here without context is the definition of "out of context"... pretty straightforward.

    Quote Originally Posted by InertiaMan View Post
    At any rate, since we're now on the same page, lets get back to science.
    Thank god... no but I'll take some measurements and post this weekend.
    Do you have any measurements on Stan's rims, which have the enlarged BSD hypothesized to cause this phenomenon?
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  6. #56
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    Quote Originally Posted by meltingfeather View Post
    It's unfortunate that you bring infantile emotional rhetoric to a mostly valuable thread. Clean up your diaper and regroup.
    Limiting the discussion to the relevant (this thread) context so we can all easily be on the same page, I did not say that pressure does not contribute.
    I can not ignore the fact that the data demonstrated that it did not in my case; if you'd like to take that up analyze my measurements to support your position.
    I said you are wrong because my results and numerous others clearly show you are. Pressure is not the sole responsible mechanism as you proclaimed.
    you can cut the derogatory comments please
    what other mechanism is responsible then? please meltingfeather fill us in on this valuable information you have

  7. #57
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    u can look at post 37

  8. #58
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    Tire Pressure and Spoke Tension

    Quote Originally Posted by WaXed64 View Post
    you can cut the derogatory comments please
    Agreed.
    Quote Originally Posted by WaXed64 View Post
    what other mechanism is responsible then? please meltingfeather fill us in on this valuable information you have
    I'm going to look past the sarcasm/snark, and answer this question directly.
    First, did you read the thread? From your first post through this one it seems very much like you haven't or you wouldn't be asking the question "what's the mechanism" all smugly and sarcastically when that mechanism is the subject of 90% of the thread. You might understand my initial response better if you read the thread.
    Second, it clearly says throughout, and as supported by my data, that the compression of the rim due to Stan's design of interference fit between BSD and tire bead was responsible in my case, which makes your proclamation that pressure is responsible based on reading one post irresponsible (for not bothering to read the thread) and... wrong.
    Maybe the tension drop from the rim compression by the tire bead was large enough to mask all pressure effects... it must have been, since I saw no effects of pressure over a very wide range.
    IM's results clearly show pressure effects, so, once again, my conclusion is, "it depends"... on circumstances, and each can clearly play a dominant role.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  9. #59
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    Half the conflict on this thread is probably because we're mixing two similar-but-different topics: a) what explains the weird observations of the Crest wheel in post #1, and b) what can be generally said about bike wheel spoke de-tensioning in response to tire mounting/airing (especially the case of MTB tubeless wheels). This thread started with (a) but has defacto shifted to (b) for better or worse.

    MF, your wheel example has the unique role of being the origin of this thread, for which I'm grateful. However, unless I missed an example, it is also the ONLY wheel which has exhibited virtually no de-tensioning due to air pressure. Every other wheel we have data for showed measurable de-tension due to air pressure. So I'm thinking it may not be the most representative example to discuss topic (b) above.

    First, its a Crest, an extremely light rim which would presumably be more vulnerable to possible "rim structure" issues that may/may-not be in play here. Secondly, the original data you posted was collected on an admittedly compromised wheel with spoke tensions far below normal.

    The second set of data you posted (measured on the re-tensioned wheel) helped some, but unfortunately only includes the 65psi and bead-off cases, and no intermediate pressure scenarios, or the all-important low-pressure/bead-set scenario. And the fact its after-inflation state didn't revert to its before-inflation state indicates some atypical variables may be involved.

    Don't misjudge this as criticism. The data is what it is, and its interesting. I'm just highlighting some of the unique elements of the example.

    Is it possible to fill in this data gap a bit?

    I would be highly interested to see measurements taken on a new/solid/tensioned Crest build, so we can compare to the data from post #1. Perhaps it will be very similar, and we can confirm that there is a fairly unique response of Crest rims to pressure/bead interaction. Or perhaps the data will be different (more similar to the non-Stans rims in my data, showing some measurable de-tensioning with air pressure) and we will learn that the wheel that inspired this thread was an anomaly in the larger picture, perhaps due to its compromised integrity and relatively "weak" rim structure.

    Anyone with a solid Crest wheel and a tensionmeter?

  10. #60
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    Interesting thread.

    Wouldn't it be really easy to figure out if Derby was on to something? Excuse my rim model number ignorance if there is already data I missed above, but has anyone tried measuring changes on a triple box x-section, or single wall vs a regular double wall as Derby pictured?

  11. #61
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    Quote Originally Posted by Zowie View Post
    Wouldn't it be really easy to figure out if Derby was on to something? Excuse my rim model number ignorance if there is already data I missed above, but has anyone tried measuring changes on a triple box x-section, or single wall vs a regular double wall as Derby pictured?
    No data in this thread for triple box or single wall. I could get some triple box data from an i23 I suppose, but it may force me to find a compressor to re-seat the bead.

    A straightforward experiment to partially test Derby's hypothesis (which is specific to Stans Crest) would be to take a series of rim width measurements with a digital caliper at various inflation pressures. If the width is invariable, it arguably disproves Derby's explanation, since he clearly expects the top edge of the rim to move outward. If width IS changing consistently, then it would be consistent with Derby's hypothesis (though not proof of it . . . in theory you could have the rim wall expand without the pivoting/rising of the spoke bed).

  12. #62
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    Quote Originally Posted by InertiaMan View Post
    Half the conflict on this thread is probably because we're mixing two similar-but-different topics: a) what explains the weird observations of the Crest wheel in post #1, and b) what can be generally said about bike wheel spoke de-tensioning in response to tire mounting/airing (especially the case of MTB tubeless wheels). This thread started with (a) but has defacto shifted to (b) for better or worse.
    Two different topics indeed. My problem, and the one experienced by others with Stan's rims who have posted, was a wheel that could not maintain enough tension to be durable... and what to do about that.
    It really doesn't matter to me whether air pressure drops my tension some if it's still enough tension to keep the wheel stable. Sort of a, "mildly interesting but of little practical use or importance" (to me) type of thing.

    Quote Originally Posted by InertiaMan View Post
    MF, your wheel example has the unique role of being the origin of this thread, for which I'm grateful. However, unless I missed an example, it is also the ONLY wheel which has exhibited virtually no de-tensioning due to air pressure. Every other wheel we have data for showed measurable de-tension due to air pressure. So I'm thinking it may not be the most representative example to discuss topic (b) above.

    First, its a Crest, an extremely light rim which would presumably be more vulnerable to possible "rim structure" issues that may/may-not be in play here. Secondly, the original data you posted was collected on an admittedly compromised wheel with spoke tensions far below normal.
    The Crest is a very representative example of rims people have had this problem with. In terms of the larger "b" discussion, maybe not, but like I said above, even a measurable and theoretically predictable drop in tension from pressure is not something I care about unless it is a problem. It's not surprising that it would happen and it makes sense. I expressed surprise at my lack of observation of pressure-related tension drop in one of my first posts.

    Quote Originally Posted by InertiaMan View Post
    I would be highly interested to see measurements taken on a new/solid/tensioned Crest build, so we can compare to the data from post #1. Perhaps it will be very similar, and we can confirm that there is a fairly unique response of Crest rims to pressure/bead interaction. Or perhaps the data will be different (more similar to the non-Stans rims in my data, showing some measurable de-tensioning with air pressure) and we will learn that the wheel that inspired this thread was an anomaly in the larger picture, perhaps due to its compromised integrity and relatively "weak" rim structure.
    A huge variable is going to be the actual tire (even beyond make and model) used, since the interference of the fit is a critical determinant of the drop, and it varies, even within tires of the same make, model & production run.

    Quote Originally Posted by InertiaMan View Post
    Anyone with a solid Crest wheel and a tensionmeter?
    The retensioned Crest I measured and reported on has been in service for over two years without issue.
    I didn't repeat the pressure variation for the retensioned wheel because I had already determined that pressure was minor if contributing at all and it seemed like a waste of time at that point. I was and remain relatively uninterested in the "b" topic.
    I'm not meaning to be dismissive, just demonstrate my perspective.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  13. #63
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    Quote Originally Posted by WaXed64 View Post
    I did actual test on a Enve 26" AM carbon rim and had 117kgf spoke tension without tire mounted mounted tire and pump to 2bar recheck spoke tension reading indeed went down to 95kgf
    Waxed64,

    Can you do another measurement of this wheel, with low/no pressure but the bead still seated?

    I'm curious how Enve compare to LB and Stans in that tire state.

  14. #64
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    Quote Originally Posted by meltingfeather View Post
    Two different topics indeed, one with a practical application/problem to solve, and one that seems more about theoretical musings with little practical application.
    I guess I disagree about the practical benefits of topic (b). This thread has had a practical influence on my wheelbuilding, even on non-Stan's rims. I was surprised to learn that we have spoke tension differences of 20-30kgF between bare wheel and the same wheel with tubeless tires installed at typical operating pressures. The scale of that tension reduction is on par with the optimal tension window on a given wheel (100-120kgF for example). My practical takeaway, especially for tight tubeless tire/wheels, is to push bare-wheel tensions toward the high side of recommended to ensure that the wheel remains in a sufficiently high-tensioned state during actual use with a tire installed. In the past, I was more conservative with the tensions, often aiming for middle of the range. Net effect, my tubeless builds are now tensioned 10kgF higher, or more, than in the past.

  15. #65
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    Quote Originally Posted by InertiaMan View Post
    I guess I disagree about the practical benefits of topic (b).
    Well I'm glad it came up then.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

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