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  1. #1
    Senior Member intron's Avatar
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    wheel builder's tension

    when you build a wheel(hubs+rims+skewers+spokes). do you perform a final tensioning of the spokes when the tire is mounted at max PSI? is this the proper method? i would think this all correlates to rider specific preferences, but in general are you suppose to perform a final adjustment of wheel spokes with a tire mounted at the PSI that the rider requires/prefers?
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    No longer in Wimbledon... womble's Avatar
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    I'm a bit of a wheelbuilding newbie, but I've read several different sets of wheelbuilding instructions, and been instructed professionally. Never heard mention of tensioning or tweaking with the tyre mounted. In fact, I wouldn't expect the pressure caused by a tyre to be significant compared to the tension of the spokes. It's not like you hear lots of popping noises when you pump up the tube, is it?

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    I have never heard of putting the tire on to do that. There is an ideal tension for ever wheel, it doesnt vary by rider unless he likes to replace spokes.
    The spoke tension is dependant on the rim, the weakest part of the wheel. The manufacturer should be able to give you an ideal tension. Typically I find it to be between 100-110kgf.
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    Senior Member juicemouse's Avatar
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    Quote Originally Posted by intron
    when you build a wheel(hubs+rims+skewers+spokes). do you perform a final tensioning of the spokes when the tire is mounted at max PSI? is this the proper method? i would think this all correlates to rider specific preferences, but in general are you suppose to perform a final adjustment of wheel spokes with a tire mounted at the PSI that the rider requires/prefers?
    I seem to remember "The Book" suggesting that you should bring the wheel up to its final tension without a tire mounted. I think it said that the tire pressure does indeed affect spoke tension a little (reduces it, I think). Going by that reasoning, if you were to tension them with the tires mounted, they would be overtensioned as soon as you removed them. Maybe someone with ready access to the book could verify this?
    It is my belief that every person in this world has something to teach, and everything to learn.

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    As a point of reference, I just finished tearing down and rebuilding a rear wheel using the original spokes and hub. Using the Park tensionometer, final drive side tension was 24 indicated on the gauge. This is equal to 107 kgf, per the conversion chart for a 2.0 mm straight gauge spoke. After installing the tire and inflating to 120 psi, the spoke tension dropped to 22.5. This is equal to 90 kgf, per the Park chart.

    The Park tool is very very well built. I like it and recommend it.

    Side comment. I struggled to make spoke adjustments on the wheel (finally) after 800 original miles, since October 2005. The nipple to spoke interface was very tight. I knew to expect this. When I bought the bike, the LBS owner said he Loctited (tm) the spokes so I wouldn't have to make unnecessary trips back to his store. I was able to salvage the spokes using a wire brush to clean away the residue. With my model helicopters, using a lot of 2.5mm and 3.0mm fasteners I use taps and dies to clean Loctite from threads after I crash and rebuild. Loctite is great stuff. I love it. Never had a helicopter part come loose. Use it judiciously. In this case, I did not have a 2mm tap to chase the threads and just running the spoke into the nipple was not effective in clearing out all the Loctite, I guess. I used linseed oil to rebuild, with new nipples.

  6. #6
    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by intron
    when you build a wheel(hubs+rims+skewers+spokes). do you perform a final tensioning of the spokes when the tire is mounted at max PSI? is this the proper method? i would think this all correlates to rider specific preferences, but in general are you suppose to perform a final adjustment of wheel spokes with a tire mounted at the PSI that the rider requires/prefers?
    Tire pressure has no noticeable effect on spoke tension.

    When I'm building a wheel and bringing it up to tension, I'm also working on the vertical truing. This cannot be done if there's a tire in the way.

    See: http://sheldonbrown.com/wheelbuild

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  7. #7
    legalize bikes
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    Quote Originally Posted by Sheldon Brown
    Tire pressure has no noticeable effect on spoke tension.

    [/CODE]
    it depends what you mean by noticeable. if you 'notice' the spoke tension with a tensiometer with a tire at max psi, it is noticeable!

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    After rebuilding my rear wheel yesterday, an Alex AT400 rim, 700x23, tensioned to "23" indicated on the Park tool (equivalent to 95 Kgf) , with the tire unmounted, I mounted my tire and took a 16 mile test ride. Felt good. This morning, I rechecked my work. Unmounted the tire checked rim and face runouts. Everything just fine. But what the heck, so I kicked up tension by about 1/4 nipple turn; did all the stress relieving and ensured any spoke windup (for the quarter turn adjustment) was addressed. Final spoke tension, checked with the Park tool was 24 (107 Kgf per the chart), on the nose. But then I find this post, from July 2005. So, I mount the tire and rechecked spoke tension, with the tire inflated, at 22.5 indicated, thought it was interesting, and submitted my observation.

    Took the bike for a 30 mile ride this evening. Temperatures were at 57 degrees-F in southern New Jersey and sunny, although the sun was low on the horizon at 4:00 pm. By 6:00 pm it was dark and 40 degrees-F. Great ride.

    Between the two spoke tensions measured, there was no noticeable difference in the ride between yesterday and today.

    My curiosity did compel me to double-check my work this evening The quantitative results, checking two sets of wheels, follow:

    Alex AT400 rim/wheel
    Rear Inflated tire spoke tension 23 (95 Kgf)
    Rear Uninflated tire spoke tension 24 (107 Kgf)
    Front Inflated tire spoke tension 19 (62 Kgf)
    Front Uninflated tire spoke tension 21 (76 Kgf)

    Alex DA16 rim/wheel
    Rear Inflated tire spoke tension 25 (95 Kgf)
    Rear Uninflated tire spoke tension 26 (107 Kgf)
    Front Inflated tire spoke tension 21 (85 Kgf)
    Front Uninflated tire spoke tension 22 (76 Kgf)

    Since the Park tool only reads in whole numbers (21, 22, 23, etc) and the graduations are so close to each other, the low side readings were always rounded up to the next higher whole number, to avoid confusion. The numbers are what they are. Tire inflation seemed to influence measured spoke tension, by about one division, and at least, and in the range of, 9 Kgf. For my wheels and the way I measured, you pump up the tire and the spoke tensions go down by a clearly measureable (9 Kgf) amount. Significant. I do not think so. Each set of wheels has about 800 miles, with no broken or loosened spokes.

    I just got the Park tool this week for my birthday present. Great little invention.

  9. #9
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    Quote Originally Posted by bmoke
    Alex AT400 rim/wheel
    Rear Inflated tire spoke tension 23 (95 Kgf)
    Rear Uninflated tire spoke tension 24 (107 Kgf)
    Front Inflated tire spoke tension 19 (62 Kgf)
    Front Uninflated tire spoke tension 21 (76 Kgf)

    Alex DA16 rim/wheel
    Rear Inflated tire spoke tension 25 (95 Kgf)
    Rear Uninflated tire spoke tension 26 (107 Kgf)
    Front Inflated tire spoke tension 21 (85 Kgf)
    Front Uninflated tire spoke tension 22 (76 Kgf)
    Are these averages of the whole wheel or individual spokes? When there is dish you should only be concerned about the tension of the tightest side (ie: rear drive side spokes).
    Don't spray WD-40 in/on it. WD-40 is a TEMPORARY WATER DISPLACER, not a long term oil.

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    I have also read somewhere that the spoke tension reading is supposed to taken with no tire pressure. I did check to see if tire pressure made a difference and I was able to see a drop in spoke tesnion while inflating the tire. I can't remember how much but the tensionmeter definately picked it up. If you have a tensionmeter all you have to do to finds out is try it. The resultes might vary from system to system I don't know because I only tried it once.

  11. #11
    Really like your peaches
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    If you true with the tyre mounted, you risk the nipple eating through the rim tape and into the tube.

  12. #12
    Senior Member juicemouse's Avatar
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    Quote Originally Posted by tharold
    If you true with the tyre mounted, you risk the nipple eating through the rim tape and into the tube.
    Not likely.
    It is my belief that every person in this world has something to teach, and everything to learn.

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  13. #13
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    Quote Originally Posted by Sheldon Brown
    Tire pressure has no noticeable effect on spoke tension.
    Oh, Sheldon, and you such a musician! Your ears will tell you differently.

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    Quote Originally Posted by Primo Tiki
    Are these averages of the whole wheel or individual spokes? When there is dish you should only be concerned about the tension of the tightest side (ie: rear drive side spokes).
    Primo Tiki, for the rear wheel, only a drive side spoke was measured and the value was representative of that drive side. For my rear wheel in question, my dish was equal, both sides. Front wheels are radial laced. Rear wheels are 3x. I never thought to check spoke tension with the tires mounted and inflated. Only this original post tweaked my curiosity and I thought the measured results were interesting. I always check rim and face on anything that spins and, in this case, that requires the tire is unmounted when truing the rim. I can always remove my Specialized Mondo tires from the rim in less than 60 seconds with three tire levers and then re-mount the tire and tube in less than 60 seconds, using only my fingers. So it is both practical and good practice to remove the tire when truing. Of course, for another tire type (and I'll skip brand names) it can be painful to stretch a tire bead over the rim, even using levers. I am not happy with the disparity between wheel spoke tensions that I noted and this can be addressed (maybe even today). Philadelphia Inquirer newspaper says temperatures will hit 59 deg-f today. So, maybe the touchup work will be deferred until tomorrow. I have a three day weekend that I am looking at. Have a great weekend.

  15. #15
    Senior Member Deanster04's Avatar
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    Never!!! You need to de-stress the wheel each time you change the tension on the wheel and it would be hard to do that with the tire on and get a proper grip on the rim. At least the way I do it. I also want to hear the spokes relax.

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    When you mount a tire and inflate it, it expands in all directions (air pushing again the inner tube and "constrainted" by the tire and rim). If you inflate it to 100psi, then there's a 100 psi pressure pushing on the rim. This pressure reduces the tension on the spokes because the pressure is uniformly all over the rim-->the air pressure is "crushing" against the rim.

    When I first started building wheels, I always check it before and after mounting the tires...but unless I didn't mount the tires right, I never need to retrue it after mounting the tires. After the first few builds (and rebuilds), I never bother to retension after putting on the tires. I do, however, recheck the tensions after the spokes are set for a while. But of course I only do that because I like to keep trueness/roundness variances down to less than 0.5mm...

  17. #17
    Senior Member Deanster04's Avatar
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    Don't mean to be a techno geek but the compressive load on a round object will have no effect on spoke tension because the metal won't shrink. The load is transferred tangentially or something like that. The spoke loading on the wheel once it is uniformally under tension so the wheel is round and laterally true it is independent of the tire except where the tire is in an upward tension on the rim trying in vain (one hopes) to remove itself from the rim. Luckily the forces also push to the side keeping the bead in its proper location.

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    I think you can do it either way, but it does make a difference. With some experimenting I found that it can make a measureable change to the rim centering on the rear wheel, probably not enough to cause a problem though. My experience has been more like what bmoke said above.

    Al

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    Deanster04, I am fine with the theory. Now, have you empirically tested your theory. Have you measured spoke tension under the two conditions that the very original poster posed. I have heard a lot of theory. Now, show me.

    I measured the tensions and they were clearly different by a full graduation as measured on the Park tool. I am not going to say the difference is significant or not. But the difference was quantifiable. There is a number and it moved consistent with the inflation or deflation of the tire. The amount was in the range of 9 Kgf. Tire pressure made an observable difference. My rims may be constructed of some alloy with physical properties that do not conform to your theory. Seems like I am the only person who has actually measured and reported on this unnatural phenomenon that is not consistent with theory. What have you or others actually measured.

    Now, after all this, where the tire hits the road, will I make any adjustments in how tight I approach tensioning a wheel without a tire mounted. NO. NO. NO. Absolutely not. But, if I measured my tension with a tire mounted and inflated, I will use this experience to suggest that maybe I do not need to tweak the tension up a tad, or that after a ride I need to Loctite the spoke so they do not loosen anymore.

    Oh, just came back from 46.4 mile group ride, 16.6 mph, through some rolling hills (or were they mountains) sponsored by First State Velo Sports (FSVS). Time 2:47:41 in the saddle. Temps at the start were 44 deg-F and 58 deg-F at the finish. It was breezy. Tomorrow is Sunday. I think I will take the day off.

    Bill M.

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    Senior Member juicemouse's Avatar
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    Quote Originally Posted by Deanster04
    Don't mean to be a techno geek but the compressive load on a round object will have no effect on spoke tension because the metal won't shrink. The load is transferred tangentially or something like that. The spoke loading on the wheel once it is uniformally under tension so the wheel is round and laterally true it is independent of the tire except where the tire is in an upward tension on the rim trying in vain (one hopes) to remove itself from the rim. Luckily the forces also push to the side keeping the bead in its proper location.
    The first rule of theory writing is that it must describe reality. Since this one clearly doesn't, it's bogus.
    It is my belief that every person in this world has something to teach, and everything to learn.

    In memory of Jim Price (aka. sydney) ...

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    The following is a quote Ric Hjertberg of Wheelsmith. It can be found here

    http://www.promechanics.com/tutorial/refine.htm

    "Spoke tension is one of those wheel variables that a field mechanic must understand. Remember that measured tension will go down about 20% when a high pressure tire is inflated. This is normal and OK, just don't mistake an inflated wheel for one that has "loosened up." Wheelsmith's preference for 80-100 kgf refers to a bare, pressure-less wheel."

    I have used a spoke tensionmeter to check spoke tesnion with and without tire pressure. It definately makes a significant difference.

  22. #22
    Senior Member Deanster04's Avatar
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    Well I have never tested my wheels with a tire on and inflated, but I am never too old and jaded to think that I know everything...I don't. I have never had the occasion to measure spokes with the tensiometer after the wheel has been finished. Usually after iteratively adjusting the vertical and lateral true and de-stressing the wheel several times I have never found the need to do any more.
    However, I am getting ready to build out a set of wheels with record 10spd hubs, 32H, 3X, and Mavic OP rims and I will try it. Always interested in learning new things (love science). What I said stands in theory (idealized case), however I didn't take into account the deformation of the rim by the tire and after thinking about it it is a plausible factor in spoke tension. I do find the figure of 20% a little extreme though, but you never know what spoke tension, rim, or spokes that figure was based on.
    Thanks for the input on this. I am an engineer and have been facinated by bikes and the physics of cycling. I found my optimal tension after studying the effect of time and miles looking at the change in size and shape of the hub spoke hole. The tension I now use is at the top end of DTSwiss and Mavic's recommendations for my setup. I have come to the same belief of Gerd Schranner that tighter is better for the wheel in the dynamic state.
    This is another opportunity to learn something about the wheel. I would be interested in hearing from someone who has tried this test on tubular tires. The tire sits more passively on the rim and there is less applied force on the rim by the tire and tube. The shape of the rim X-Section is different. Let me know if you have tried this.
    Thanks again and good riding.
    Last edited by Deanster04; 01-22-06 at 12:03 AM. Reason: addition

  23. #23
    Senior Member juicemouse's Avatar
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    Quote Originally Posted by Deanster04
    This is another opportunity to learn something about the wheel. I would be interested in hearing from someone who has tried this test on tubular tires. The tire sits more passively on the rim and there is less applied force on the rim by the tire and tube. The shape of the rim X-Section is different. Let me know if you have tried this.
    Thanks again and good riding.
    That would be an excellent test to pinpoint where the forces are being developed that lead to decreased spoke tension. I would never have thought of that. All the side forces have to cancel each other out, so all that's left are the radial forces. My hypothesis would be that the tubular wheel spoke tension would still be decreased, but not by as much as the clincher wheel. Now if only I had my vintage bike (with sewups) up here at school with me...
    It is my belief that every person in this world has something to teach, and everything to learn.

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    Quote Originally Posted by Deanster04
    Don't mean to be a techno geek but the compressive load on a round object will have no effect on spoke tension because the metal won't shrink. The load is transferred tangentially or something like that. The spoke loading on the wheel once it is uniformally under tension so the wheel is round and laterally true it is independent of the tire except where the tire is in an upward tension on the rim trying in vain (one hopes) to remove itself from the rim. Luckily the forces also push to the side keeping the bead in its proper location.

    Materials do compress under load. Would you take a thin sphere submarine down a couple miles into the ocean? I mean if it doesn't compress, you don't have much to worry about, right?

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    No, do the final tension without a tire. Regardless of whether or not a tire changes tension of the wheel, final tension on a wheel is done without a tire.

    That said, the data posted here is interesting and deserves further study. I think I'm going to check a few wheels when I get a chance.

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