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Tensiometer curiosity
Having yet to build my first wheel, I have a question about tensiometers.
Is the absolute measure of (whatever - isn't it really a distance deflection rather than a force, although threads tend to indicate that it reads in force) that critical? OR, is the only thing critical its ability to give the same reading on the same spoke (and spokes with the same tension) consistantly? In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? |
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#2
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Tensiometer curiosity
On Mar 31, 7:28 am, richard wrote:
Having yet to build my first wheel, I have a question about tensiometers. Is the absolute measure of (whatever - isn't it really a distance deflection rather than a force, although threads tend to indicate that it reads in force) that critical? OR, is the only thing critical its ability to give the same reading on the same spoke (and spokes with the same tension) consistantly? In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? IMO, knowing that spoke tension is consistent from spoke to spoke (i.e., "relative" spoke tension) is more critical than knowing the "absolute" spoke tension to a really great degree of accuracy (IOW, 95Kgf v. 105Kgf is not a big deal). |
#3
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Tensiometer curiosity
On 2007-03-31, Ozark Bicycle wrote:
On Mar 31, 7:28 am, richard wrote: Having yet to build my first wheel, I have a question about tensiometers. Is the absolute measure of (whatever - isn't it really a distance deflection rather than a force, although threads tend to indicate that it reads in force) that critical? OR, is the only thing critical its ability to give the same reading on the same spoke (and spokes with the same tension) consistantly? In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? IMO, knowing that spoke tension is consistent from spoke to spoke (i.e., "relative" spoke tension) is more critical than knowing the "absolute" spoke tension to a really great degree of accuracy (IOW, 95Kgf v. 105Kgf is not a big deal). This is something I've never understood. I don't bother with a tensiometer myself, but surely if the spoke tensions aren't all about the same then the wheel will be out of true? And if the only way to get it true is with uneven tensions (if for example the rim isn't round and flat in the first place), then you probably need uneven tension since you will obviously require the wheel to be true. I suppose if every other spoke on each side was loose you could have a true wheel with uneven tension, but there's a minimal chance of that happening by mistake. |
#4
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Tensiometer curiosity
On Mar 31, 8:27 am, Ben C wrote:
On 2007-03-31, Ozark Bicycle wrote: On Mar 31, 7:28 am, richard wrote: Having yet to build my first wheel, I have a question about tensiometers. Is the absolute measure of (whatever - isn't it really a distance deflection rather than a force, although threads tend to indicate that it reads in force) that critical? OR, is the only thing critical its ability to give the same reading on the same spoke (and spokes with the same tension) consistantly? In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? IMO, knowing that spoke tension is consistent from spoke to spoke (i.e., "relative" spoke tension) is more critical than knowing the "absolute" spoke tension to a really great degree of accuracy (IOW, 95Kgf v. 105Kgf is not a big deal). This is something I've never understood. I don't bother with a tensiometer myself, but surely if the spoke tensions aren't all about the same then the wheel will be out of true? It ain't necessarily so..... And if the only way to get it true is with uneven tensions (if for example the rim isn't round and flat in the first place), then you probably need uneven tension since you will obviously require the wheel to be true. That is a slightly different situation, but even then, having a balance between true/round and even/balanced tension is the best compromise. I suppose if every other spoke on each side was loose you could have a true wheel with uneven tension, but there's a minimal chance of that happening by mistake. I guess that depends on your definition of "loose". If by "loose" you mean the tension is too low, that is not uncommon. Too high on some spokes, too low on others; it happens all the time. |
#5
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Tensiometer curiosity
richard wrote:
Having yet to build my first wheel, I have a question about tensiometers. Is the absolute measure of (whatever - isn't it really a distance deflection rather than a force, although threads tend to indicate that it reads in force) that critical? OR, is the only thing critical its ability to give the same reading on the same spoke (and spokes with the same tension) consistantly? In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? relatively consistent tension is critical for a true wheel that stays true in service. however, the absolute tension is essential if you want to have a rim that doesn't crack or have eyelets that don't pull out. what most people do therefore is measure 3 or so spokes and average their absolute readings, then go around the wheel making sure other spokes have the same pitch when plucked. you'll never get all spokes identical because all rims are slightly inconsistent, but aim for the closest you can get. [spokes at the rim joint are often over-tension, so exclude them from your average.] |
#6
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Tensiometer curiosity
Ben C wrote:
This is something I've never understood. I don't bother with a tensiometer myself, but surely if the spoke tensions aren't all about the same then the wheel will be out of true? This depends a lot on the rim and the spoke count. If you use a strong, stiff rim with 32 or 36 spokes, for example a typical MTB wheel, you can have one spoke a lot looser than the others without the wheel being out of true - As long as the adjacent spokes are very tight. On the other hand, if you build a front wheel with a lightweight road rim and only 24 or 28 spokes what you say is closer to truth. -as |
#7
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Tensiometer curiosity
In article ,
Ben C wrote: On 2007-03-31, Ozark Bicycle wrote: On Mar 31, 7:28 am, richard wrote: Having yet to build my first wheel, I have a question about tensiometers. Is the absolute measure of (whatever - isn't it really a distance deflection rather than a force, although threads tend to indicate that it reads in force) that critical? OR, is the only thing critical its ability to give the same reading on the same spoke (and spokes with the same tension) consistantly? In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? IMO, knowing that spoke tension is consistent from spoke to spoke (i.e., "relative" spoke tension) is more critical than knowing the "absolute" spoke tension to a really great degree of accuracy (IOW, 95Kgf v. 105Kgf is not a big deal). Well, most tensiometers don't give you a flawless absolute measurement for reasons that have been discussed in other threads. They do give you a ballpark measurement that is IMHO close enough to be getting on with. There are techniques for finding the highest tension the rim can withstand to maximize the load the wheel can carry, but most people probably don't need to have their wheels quite that tight since they don't load the wheel that heavily. This is something I've never understood. I don't bother with a tensiometer myself, but surely if the spoke tensions aren't all about the same then the wheel will be out of true? And if the only way to get it true is with uneven tensions (if for example the rim isn't round and flat in the first place), then you probably need uneven tension since you will obviously require the wheel to be true. Take wheels at random and pluck them and you will often find that there are some spokes that are much tighter than others. That's because the lateral pull of spokes affects not on the part of the rim the spokes are connected to but also a few inches to either side. This is because of the lateral rigidity of the rim. This scenario can potentially result in the looser spoke going slack under load and the nipple backing off, which can eventually put the wheel out of true. |
#8
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Tensiometer curiosity
On Mar 31, 6:28 am, richard wrote:
In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? As others have said you can pluck the spokes to get relative tension even on each side, but a tensiometer is necessary (for me at least) to get the absolute tension correct. Generally, you want the tension as high as the rim spec (or until buckling occurs), but if tension is much lower than this, then the spokes might go slack in service which reduces the strength of the wheel, and may also result in loosening (if they aren't locktited), and early fatigue. The spoke wrench is the only tool you really need to build a wheel, but I'd say that a tensiometer is the 2nd most important. At least it is a good idea to check your spoke tension at a local shop if you don't want to buy one. It is very easy to get a wheel acceptably true, but still have tensions varying all over the place. Basically, the rim stiffness is enough to mask the variation. Sloppy building jobs are like this... including cheap machine built wheels I've had. |
#9
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Tensiometer curiosity
On 2007-03-31, Tim McNamara wrote:
In article , Ben C wrote: [...] This is something I've never understood. I don't bother with a tensiometer myself, but surely if the spoke tensions aren't all about the same then the wheel will be out of true? And if the only way to get it true is with uneven tensions (if for example the rim isn't round and flat in the first place), then you probably need uneven tension since you will obviously require the wheel to be true. Take wheels at random and pluck them and you will often find that there are some spokes that are much tighter than others. That's because the lateral pull of spokes affects not on the part of the rim the spokes are connected to but also a few inches to either side. So you could end up with, for example, one spoke that was too tight with the two either side of it on that side of the rim a bit loose, and still have a fairly true wheel since the rim's rigidity will not permit a wobble that small. This is especially possible with 36H and a rigid rim which is what Antti also said. This is because of the lateral rigidity of the rim. This scenario can potentially result in the looser spoke going slack under load and the nipple backing off, which can eventually put the wheel out of true. Which I suppose is the basic reason why even tension is desirable. |
#10
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Tensiometer curiosity
On Mar 31, 10:55 am, "Ron Ruff" wrote:
On Mar 31, 6:28 am, richard wrote: In other words, is "each spoke tightened to so many Kg" as important as knowing all spokes are tensioned equally? As others have said you can pluck the spokes to get relative tension even on each side It can be quite illuminating to set even tension by "plucking" and then go around the wheel spoke by spoke and see how even the tension truly is. |
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