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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.
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  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.
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  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.
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  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.
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  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.
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  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.
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  16. #66
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    I have another rim/tire combo datapoint which is pretty surprising.

    Rim: 32H LB 35mm hookless 29er with 14g DB spokes
    Tire: Michelin Wild Grip'r 29x2.25 installed tubeless

    Spoke tension on the brake side (front wheel) was 110kgF before tire install. With tire installed and pumped to 25 PSI, the spoke tension dropped to 85-88 kgF. With air pressure then released to zero, but beads still seated, tension returned to 110kgF.

    That's a pretty significant drop in tension, and it is apparently due only to air pressure. Seems to behave differently than the LB 30mm hooked rim, perhaps due to a different bead shoulder dimension (my LB 30mm numbers at top of thread were with a Bontrager tubeless rim strip installed).

  17. #67
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    Quote Originally Posted by InertiaMan View Post
    I have another rim/tire combo datapoint which is pretty surprising.

    Rim: 32H LB 35mm hookless 29er with 14g DB spokes
    Tire: Michelin Wild Grip'r 29x2.25 installed tubeless

    Spoke tension on the brake side (front wheel) was 110kgF before tire install. With tire installed and pumped to 25 PSI, the spoke tension dropped to 85-88 kgF. With air pressure then released to zero, but beads still seated, tension returned to 110kgF.

    That's a pretty significant drop in tension, and it is apparently due only to air pressure. Seems to behave differently than the LB 30mm hooked rim, perhaps due to a different bead shoulder dimension (my LB 30mm numbers at top of thread were with a Bontrager tubeless rim strip installed).
    That is interesting.
    Thanks for posting up the data point.
    As with most things, it seems like there are many factors at play and no rule that can be stated regarding spoke tension as relates to tire pressure and bead seating.
    "It depends" is about as good as it gets.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  18. #68
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    Quote Originally Posted by InertiaMan View Post
    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.

    from memory the ENVE with no air pressure spoke tension went back up to 105kgf (bead still seated) and then back up to 117kgf after bead unseated
    tires were schwalbe TLR 2.25 (so bead seat probably not as tight as UST)
    My thinking is basically the tighter the bead on the rim the more effect of spoke tension reduction it will create, however tire pressure will push on the rim bed and apply opposite force on the tire to pull the bead pressure off the rim (tire pressure also forces the bead up onto the bead to start with)

    composites have very good tensile strength, however a spoked wheel is under a compression load

    I guess the more compressive rigidity a rim has, the less will be the effect of spoke detensioning from tire pressure

    In all respects the ENVE AM suffers a hell lot more spoke tension variations than the Alu ZTR Flow rims I have.... very unimpressed

    what I have also noted is that temperature also had a measurable effect on the ENVE wheel spoke tensions ie. when temp goes down the spoke tensions also drop further... ( I put this down to the carbon composite rim contracting with drop in temperature)
    the spokes shpould also contract but I guess it must not be at the same rate
    on the ENVE AM I measured around 10kgf lower going from 25degC down to 15 degC ....

  19. #69
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    Quote Originally Posted by meltingfeather View Post
    The retensioned Crest I measured and reported on has been in service for over two years without issue.
    to clarify did you re-tension with the tyre still fitted and inflated?

    I have a similar issue with the crest that seems to be tight TLR bead rather than pressure related.
    What exactly is a rigid hard tail?

  20. #70
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    Quote Originally Posted by WaXed64 View Post
    what I have also noted is that temperature also had a measurable effect on the ENVE wheel spoke tensions ie. when temp goes down the spoke tensions also drop further... ( I put this down to the carbon composite rim contracting with drop in temperature)
    the spokes shpould also contract but I guess it must not be at the same rate
    Many plastics have a heat expansion rate ten times larger than steel. Your observation makes perfect sense.

  21. #71
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    Quote Originally Posted by Stuart B View Post
    to clarify did you re-tension with the tyre still fitted and inflated?
    No.

    Quote Originally Posted by Stuart B View Post
    I have a similar issue with the crest that seems to be tight TLR bead rather than pressure related.
    I raised the tension to an average of 106 kgf and the wheel has not been back (though the guy moved to Colorado).
    I also suspect the rim has now been replaced... the guy rides a LOT.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  22. #72
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    Re: Tire Pressure and Spoke Tension

    Quote Originally Posted by meltingfeather View Post
    No.


    I raised the tension to an average of 106 kgf and the wheel has not been back (though the guy moved to Colorado).
    I also suspect the rim has now been replaced... the guy rides a LOT.
    OK cheers .


    sent from my phone so apologies for any typos
    What exactly is a rigid hard tail?

  23. #73
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    Quote Originally Posted by Saul Lumikko View Post
    Many plastics have a heat expansion rate ten times larger than steel. Your observation makes perfect sense.
    Carbon/epoxy composite have up to 10x less thermal expansion rate than steel:

    Mechanical Properties of Carbon Fibre Composite Materials

  24. #74
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    I just unseated my tyre and checked tension as it was pretty much as set before mounting the tyre. So I just upped the tension a bit a re-dished to try and account for the change in dish after the tyre is mounted.

    While pumping up and re-seating the bead I watched my tension gauge, initially it went down with pressure as the bead seated, each time the bead popped the tension went down suddenly. I then let all the air out and the tension remained where it was....so I believe in my case it is the incredibly tight bead. Tight enough I think I am going to buy some new tyre levers!

    the upside is they are the easiest tyre I have had to inflaste with a track pump! not sure its worth the trade off for spoke tension though.

    maybe I should have gone for the arch ex, but the crest were 30% off
    What exactly is a rigid hard tail?

  25. #75
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    Leonard Zinn discusses this topic here:
    http://velonews.competitor.com/2011/...tension_198452

    Tire pressure does indeed reduce wheel spoke tension. Perhaps not all rim/spoke/hub/lace pattern/tire equally, but it does. I don't understand why Meltingfether would challenge this pretty well-established fact.

    So here's my question. Why not run up final tension on a road wheelset - especially those with more dish and/or aluminum nipples and/or zero-offset rim holes (which cause even more nipple friction) - with tires at full inflation - or even overinflated?

    I know when I'm reaching optimal drive-side tension, nipple friction gets very high. Yes, I use lubrication and/or thread lock on both thread and rim interfaces. I've only stripped a few nipples in the last several years, so it isn't like I'm experiencing nipple failure on a regular basis. But man, those nipples sure get hard to turn! Seems that instead of pushing nipples to their maximum applying so much torque, just install tires, inflate to 20 to 40 psi over tire's printed maximum* so you can achieve high final tension much easier. Plus, it gives the hands a break when building multiple wheel pairs.

    I realize that final radial truing will be difficult to impossible to achieve with the tire installed. At least the lion's share of nipple tightening will be done more easily. Once optimal tire-on tension is achieved, remove tire and conduct final radial and lateral true.

    I have not tried this. Nor have I researched this idea much online. But I thought I'd poke my head in on this thread to ask if any of the wheel builders are doing this as part of their building procedure.

    When thinking back to a personal rear wheel build, I now realize tire pressure spoke detensioning was responsible for NDS spoke loosening. I didn't utilize a spoke tensionmeter at the time and just accepted the fact that 9+ speed rear wheels had so much dish, loose NDS spokes were hard to avoid.

    Seems like utilizing tires would be a way to achieve high tension without killing nipples and one's hands during builds.

    *Tire max pressure rating is determined by inflating a tire properly on an industry standard rim and inflating it until it pops off. The pressure at which it pops off is divided by 2 and that's the tire's max pressure. So going 20 to 40 psi over a tire's max. pressure rating is usually going nowhere near blow-off pressure (assuming an industry standard rim or equivalent is used).

  26. #76
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    Tire Pressure and Spoke Tension

    Quote Originally Posted by TandemBear View Post
    Tire pressure does indeed reduce wheel spoke tension. Perhaps not all rim/spoke/hub/lace pattern/tire equally, but it does. I don't understand why Meltingfether would challenge this pretty well-established fact.
    I didn't. It would help if you read the thread.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
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  27. #77
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    Quote Originally Posted by meltingfeather View Post
    I didn't. It would help if you read the thread.
    I guess I either perused it too quickly or missed the first page. The post I saw of yours seemed to challenge this. Sorry to have missed the intent of your comment.

    Either way, thanks for providing some good discussion on the issue. I'll give the thread more attention when I have a moment to do so.

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    Quote Originally Posted by TandemBear View Post
    I guess I either perused it too quickly or missed the first page. The post I saw of yours seemed to challenge this. Sorry to have missed the intent of your comment.

    Either way, thanks for providing some good discussion on the issue. I'll give the thread more attention when I have a moment to do so.
    No worries.

    Through this discussion it became apparent to me that both tire pressure and bead seating can and do play roles and either one can be dominant, depending on circumstances. I was actually surprised by the fact that tire pressure did not seem to play a role under my particular set of circumstances, as my first post indicates.

    It seems like most people want to take their experience and use it to theorize some universal law. Unfortunately (for them) reality, like Homey, don't play dat.
    Last edited by meltingfeather; 01-07-2015 at 05:17 PM.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  29. #79
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    I'll add my data to this thread, use it as you will. My rear tire's sealant needed to be refreshed, so I took the opportunity to check tensions and re-true.

    Chris King ISO rear hub, sapim straight spokes, brass nipples, stans arch rim, 26". Maxis Ardent EXO 2.1 tire. The bead didn't sit incredibly tight on the rim, it popped off fairly easily once deflated, but it didn't fall off on it's own either.

    https://docs.google.com/spreadsheets...it?usp=sharing

    I took the average of 4 random spokes for each set of meausrements. in hindsight I should have done all, or used the same 4 each time
    My bike MCA kinda climbs like a billy-goat. WOO WOO!

  30. #80
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    I'm getting a much bigger drop in tension with my Light Bicycle carbon rims, DT spokes, and WTB Cross Boss tire. I'm worried that if I raise the tension enough to be at an acceptable level with the tire on, it'll be too high with the tire off. The rim has a published max of 180kgf and I'm already at as much as 167 on the drive side with the tire off.

    14-53kgf, 15-58kgf, 16-64kgf, 17-70kgf, 18-77kgf, 19-85kgf, 20-94kgf, 21-105kgf, 22-117kgf, 23-131kgf, 24-148kgf, 25-167kgf.

    Some of them lost half their tension! The first DS spoke for example. That's 148 down to 70kgf.

    Drive side

    24 -> 17
    25 -> 20
    25 -> 18
    25 -> 19
    24 -> 16
    25 -> 19
    24 -> 18
    25 -> 20
    24 -> 17
    24 -> 19
    24 -> 20
    24 -> 20
    25 -> 21
    24 -> 19
    24 -> 18
    25 -> 21

    Non drive side

    19 -> 14
    21 -> 18
    19 -> 12
    19 -> 12
    20 -> 13
    21 -> 16
    20 -> 15
    19 -> 15
    19 -> 16
    19 -> 15
    20 -> 15
    21 -> 17
    20 -> 15
    21 -> 16
    20 -> 15
    21 -> 18

  31. #81
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    Quote Originally Posted by Alias530 View Post
    I'm getting a much bigger drop in tension with my Light Bicycle carbon rims, DT spokes, and WTB Cross Boss tire.
    What's the comparison here?
    Seated to unseated tire?
    Pressured to flat but still seated?
    Pressured to flat and unseated?
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  32. #82
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    Quote Originally Posted by meltingfeather View Post
    What's the comparison here?
    Seated to unseated tire?
    Pressured to flat but still seated?
    Pressured to flat and unseated?
    This is comparing to bare wheel to 40psi/seated rim bead (tubeless).

    This is a 35mm tire so 40psi is not that much.

    I don't know what to do now...

    I had the wheels built for me, kept having NDS spokes go slack, checked tension and I was at 95kgf DS/70kgf NDS and determined that to be too low so I tried to fix it and ended up starting from scratch. Then I got the wheel up to 150kgf on the DS and thought I was golden but as soon as I put the tire on I'm right back to where I started. I thought the wheel builder did a bad job but I am coming up with the same result.

  33. #83
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    Spoke tensions in the range of 150-160kgF are pretty much categorically too high, regardless of components used, especially on a 32H rim. Tensions above 130kgF are relatively rare. 120 or less is a more typical target for drive side tension.

    What model of DT spokes are you using? What model LB rim?

  34. #84
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    Quote Originally Posted by InertiaMan View Post
    Spoke tensions in the range of 150-160kgF are pretty much categorically too high, regardless of components used, especially on a 32H rim. Tensions above 130kgF are relatively rare. 120 or less is a more typical target for drive side tension.

    What model of DT spokes are you using? What model LB rim?
    DT Comp spokes and the 29er XC rim (27mm outer/22mm inner diameter) with extra layers of carbon to reach about 410g (normally 365g if I remember right).

    With the tire on some of the NDS spokes are below 50kgf... that's way too low isn't it? I still haven't gotten a consistent answer as to whether "max" and "recommended" tensions are with or without the tire on. I'm seeing a bigger gap than most apparently do, to the point that my "with tire" tensions are unusably low.

  35. #85
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    I checked your tension values on the Park cross reference table and confirmed you are reading it correctly. Presumably you are also placing the tensiometer only in the butted section of the spokes when reading. So no obvious "errors" to explain things.

    One thing I suggest you try is another tire, simply for another datapoint. The Cross Boss is designed as a tubeless cross tire, which would logically be targeted at substantially narrower rims typically used in that application. In addition, road tubeless tires are normally designed to be even tighter at the bead than MTB tires due to the higher pressures normally encountered. So if we assume that WTB designed these tires for common road/cross wheels and used a nominal bead diameter that was (relatively) small/tight, then your current rim/tire combo is sort of a worst case scenario for this tension-loss-under-tire-pressure scenario. In other words, my hypothesis is that your tire bead is tighter than anyone else on this thread that has taken sample measurements, so your before/after tire tension drops are alarmingly higher.

    Edit PS: You should also take a tension reading (a) with the tire mounted and at pressure, and (b) with tire deflated but bead still seated. If the deflated-but-seated tensions are nearly as low as the inflated tensions, then you'll know this is primarily a bead diameter issue.

    As for tension targets, you can ignore the max tension from the LB website. If anything, that is a failure tension in their testing, or some statistical threshold preceding failure My recommendation would be to shoot for 130kgF on DS without a tire. Spoke pull though is not unheard of on these rims, so I'd be hesitant to recommend higher.

    A typical no-tire tension target is 110-120kgF on the DS and >80kgF on the NDS. Unfortunately on these rims (and others), it can be difficult/impossible to get the NDS spokes > 80kgF while keeping the DS below 120. And even harder to keep the NDS spokes sufficiently high AFTER a tire is mounted. Get the spoke tensions as consistent as humanly possible, and perhaps the NDS side will be >80kgF.

  36. #86
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    The Cross Boss sidewall says the max pressure is 65psi if I remember right, which is about what a mountain bike tire usually quotes as max. The bead was tight but not any tighter than a normal tubeless mountain bike tire.

    I just checked the front wheel (same rim/spoke type but 28 spokes/bigger tubeless cyclocross tire) and the disc side spokes were at 85kgf and non-disc was at 64kgf.

    The rear wheel drive side spokes average around 95kgf and NDS average around 64kgf but some so low there's no spot on the conversion chart. I was losing spoke tension in the rear when the non drive side was at 70kgf. I guess I can try another tire or locktite the NDS threads?

    Prior to the tire I had the NDS around 90kgf and 150kgf on the DS.

    Is it possible that the spokes are too tight and that contributes to the tension drop with the tire? Is there any way that dropping the tension would result in a lower drop when I add the tire?

  37. #87
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    Quote Originally Posted by Mac_Aravan View Post
    Carbon/epoxy composite have up to 10x less thermal expansion rate than steel:

    Mechanical Properties of Carbon Fibre Composite Materials
    Yeah but if you look at UD carbon (unidirectional, that seems to be the norm these days) you will see that in one direction is actually has negative thermal expansion but in the other direction it has roughly 3x higher thermal expansion compared to steel.

    In the same direction it also happens to have 1/20 the stiffness (youngs mod) of the steel listed,
    1/20 ultimate tensile strength, and 1/4 ultimate compressive strength.

    All this could very well explain the behaviour of spokes going soft when the wheels get colder with carbon wheels.

    That is if I'm reading the table correctly, but I think I am.
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  38. #88
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    So pleased I found this thread which I’ve just read right through, and special thanks to meltingfeather and InertiaMan for their inputs. My experience with Schwalbe Hans Dampf and RockRazor mounted on Stans Arch 650B rims run tubeless…

    Just built up my first ever wheelset using Roger Mussons excellent book and determining spoke tension by pitch – using some 26” Crest wheels as a reference. Wheels were straight and true but doubts about tension got the better of me so splashed out on a Park Tensionmeter just to be sure!

    Checked front wheel disc side and the tensions were way below the 125KgF recommended on the notubes website, averaging out around 100KgF, with the NDS of course considerably lower. But this was with the tires now mounted and inflated (at this point I had no idea the tires had an effect on spoke tension).

    I adjusted the tension to ballpark 125KgF throughout, then off with the tire to check radial and lateral trueness, tweaked these in then checked tension again – 150KgF average! The penny dropped – tires in some way had an effect on tension. A couple more hours with the tire off again getting the tensions back to where they probably were in the first place when originally tensioned using pitch, 125 KgF with no tire fitted.

    On to the back wheel and this time I checked the Drive Side tension with tires inflated to around 25PSI (95KgF average), tires deflated (same), and bead unseated (125KgF).

    So in my experience with my set-up the tire is dropping tension by around 25-30KgF, and it is the bead not the tire pressure that seems to be causing this. I noticed somewhere on the web than Stans recommended tension used to be 100KgF but is now upped to 125KgF, and I wonder if this is why, because a tire mounted on their rims reduces tension so drastically?

    For now I’ve decided to leave the wheels as they are and keep an eye on the spoke tensions once the bike is finished and actually gets ridden. That is around 100KgF with tires on (which equates to 125KgF with tires off and is now Stans recommended tension)

    For info NDS tension on the rear wheel with tire mounted is considerably lower at only about 60KgF average.

  39. #89
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    Nice post and observations.

    However, given your options, I think you should opt for the higher tensions. You want the recommended spoke tension for real-world situations. That is, appropriate tensions when you're riding, not when the wheel's in the truing stand with the tires off.

    However, if the manufacturer has anticipated the resulting tension loss when tires are mounted, then you'd want to hit their posted value in the truing stand.

    It would be worthwhile to confirm with the rim/wheel manufacturers if their listed tensions are for real-world usage, or tension during building, prior to tire installation.

    Thanks again.

  40. #90
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    PS I just corresponded with Stans to ask for clarification. I'll keep an eye on my inbox and let you know if I hear from them.

  41. #91
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    I lost quite a bit of tension with my Light Bicycle rims. They said (and the Park Tensionmeter user manual) says that tension should be without a tire. Tire pressure and type play such a big role it seems like you'd want tension WITH a tire.

    I eventually gave up on mine and changed to a different tire. I would have to run such high tension without a tire to get it high enough with a tire that I'd crack the rim if I ever had a blowout. So, new tire it was.

  42. #92
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    Thanks TandemBear, I await Stans response with interest.

    One option might be to split the difference and take the truing stand tension up to say 135KgF and therefore the real world tension up to about 110KgF...This would negate any worries about the tension being too high and at the same time feeling more confident that the real world tension is high enough to support the wheel.

    Lets see if Stans reply first though as I don't relish removing the tires and tinkering a third time on this wheelset!

  43. #93
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    OK, Peter at Stan's got right back to me, which was nice since it was almost quitting time on their end of the country.

    Spoke tensions are given for bare wheels. They assume spoke tension will decrease with tires, so don't worry about it.

    I Stan(d) corrected!

    Nice to have that issue cleared up!

    PS Anyone ride the new Flow Trail at Soquel Demonstration Forest yet? Official grand opening this Saturday, but I can't make it. Can't wait to get back down there to ride - it's been WAY long. Will ride it on the half bike the first time, but hoping to hit it on the tandem, too!!!

    Demo Flow Trail of Soquel Demonstration State Forest now open - Mtbr.com

  44. #94
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    I had built a bunch of wheels and never had this problem, so I never checked for it.
    Until last year...
    I built up a pair of 35mm Velocity Blunts for my own bike. Mounted up tires (tubeless) and went for a 20 mile ride. In the middle of my ride, my bike started to feel all loose and weird. I checked my tire, figuring it was soft and it was not. Then I noticed all of my spokes were loose on my rear wheel.
    When I got home, I took the tire off and checked the wheel out. tensions were low, but not like with the tire mounted, so I mounted the tire back up and retensioned the spokes with the tire mounted. Wheel has been fine since.
    Then I realized I had just laced a set of Flows for a friend's bike build I was doing, so I mounted his tires and checked tension... Same thing. So I tensioned his with the tires on. He's been on that bike about a year now with no problems.
    This has been with Geax Saguaros on all three of these wheels. I recently built a 26" Flow and mounted up a Specialized rear tire and no change in tension.
    I guess you should always just check.
    I like turtles

  45. #95
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    As I recently considered the soon to be available Schwalbe Procore system, it made me wonder how the wheels are going to handle the increased pressure.

    Consider that Schwable recommends inflating the inner chamber to 60-90psi. That's WAY higher than any typical MTB tire setup. It scares me to think what that may do to spoke tensions, especially on wide rims. I searched online and found a couple similar comments from readers on forums elsewhere, but no response from Schwalbe about this aspect of the Procore system.

    I can imagine the spoke tension getting reduced 30-40kgF if subjected to 75psi across a 28mm internal width rim. Hard for me to imagine how to compensate for that. If you tension the wheel higher to compensate, you're looking at 150kgF+ on the rim/spoke/nipple when tires aren't mounted.

    I was excited to try the Procore setup, but this has me concerned.

  46. #96
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    Quote Originally Posted by InertiaMan View Post
    I was excited to try the Procore setup, but this has me concerned.
    I'm curious to see this as well.
    As we have seen, sometimes tire pressure affects spoke tension and sometimes it does not. Because ProCore is a pressure-containing bladder as opposed to a tube in a tire, it may and IME probably will exert less force on the rim than a tube inflated to the same pressure.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  47. #97
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    Quote Originally Posted by meltingfeather View Post
    I'm curious to see this as well.
    As we have seen, sometimes tire pressure affects spoke tension and sometimes it does not. Because ProCore is a pressure-containing bladder as opposed to a tube in a tire, it may and IME probably will exert less force on the rim than a tube inflated to the same pressure.
    I do not have a ProCore system...but it appears to me that the solution is roughly a tube in a tire. That tire may have a different bead and appears to be around 70mm b2b but it looks like a tire casing without tread. I think it's an interesting question just how different the loads are on the rim.
    Last edited by craigsj; 08-09-2015 at 05:53 AM.

  48. #98
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    Quote Originally Posted by craigsj View Post
    I do not have a ProCore system...but it appears to me that the solution is roughly a tube in a tire. That tire may have a different bead and appears to be around 110mm b2b but it looks like a tire casing without tread. I think it's an interesting question just how different the loads are on the rim.
    You're right... I was mistaken about the design.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  49. #99
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    Just sharing my data. I recently built a rear wheel with an arch ex 29 rim. Measured the tensions w/o a tire, with tire at 40 psi and with tire at 0 psi but mounted on the rim. I build the wheel a little bit over the tension spec to account for tension drop. Tire used was a fairly old maxxis icon.

    No tire DS: 135 kgf (26)
    Tire 40 psi DS: 103 kgf (23.5)
    Tire mounted 0 psi DS: 120kgf (25)

    *(park tool tm-1 unit)

    Cheers

  50. #100
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    I think rim/tire combo matters a lot. My Rovals with Maxxis tires hardly drop, but my Light Bicycle mountain bike rims with tight cyclocross tires on them lower a lot.

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