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After truing my front wheel, it seems that it is laterally true. However, the spoke tension seem very uneven, with a few spokes that are very taut next to other spokes which are more loose. If it was a small difference, I wouldn't be too concern, but it seems a bit too big of a difference in tension that has me worried.
I have access to a tension meter and a pro-grade truing stand.
How should I fix this?
Should I loosen all the spokes and start from scratch or fine tune the existing setup?
For reference, I used to work for Velomax Wheels, and Easton Wheels.
You may want to back all of the spokes off an equal amount, say 5 or 10 turns. This will give you a little bit of room for adjustment, without having to completely detention the entire wheel.
There is a book called "the Bicycle Wheel", by Jobst Brandt, that does a great job of walking you through the process of truing.
Another way to tell if the spokes are of equal tension is to pluck them like guitar strings. Since they are all of the same length and same thickness, equal tone means equal tension. (We used to attach an electronic "pick up" to our truing stands, and wear headphones so we could better hear the differences when we plucked the spokes. This shouldn't be necessary say, in your garage where there is a lot less ambient noise.)
A couple tips for truing (though you may know these already): - Be sure to back off any adjustment that you make on a singular nipple. This will eliminate any possible spoke 'wind-up" caused by the twisting of the nipple. (example - if you want to make a 1/4 turn adjustment, turn the nipple a 1/2 turn and then back off 1/4.) - Be sure to give adjacent spokes a soft squeeze to help the spokes and nipples settle. - check for cracked nipples and cracks at or near holes in rims.
Once it is true, then you can bring all spokes back up to tension (the 5 or 10 turns that you originally made.)
Truing stands are very helpful in holding the wheel in the right position to make your adjustments. (Rather than trying to do it in your hands or in the bicycle frame/fork.) they also typically have a measurement pin or finger that helps show where (and to what degree) the wheel is out of true.
Tensiometers are okay devices. Here are a couple of their downfalls: 1-no two are the same and they come out of calibration quite easily. 2-several factors, such as how you hold the tensio on the spoke and where you place the tensio on the spoke, influence the gauge reading.
Hope this helps.
If the adjacent spokes with different tension are on the same side of the wheel, then you could, to a certain amount, release the tension from the tight one and tighten the loose one.
If they are each on one side of the wheel, you could not even the tesion without untruing the wheel, and that means your rim is not intrinsically true.
If the rim is not intrinsically true (that is, it would not look true if the spokes are removed), you could try to "bend" the rim in place this way:
Although it seems too violent, it has worked as magic with my acquaintances (who sometimes bend their wheels falling during rides). Hopefully, though, the problem is just uneven tension in spokes on the same side of the wheel, so this beating would not be necessary.
Hope this helps!
The way I approach this is to equalize the tension by sound (my ear is terrible so I use an app for the iPhone called Spoke Tension Meter). I start by picking an average tension and adjusting all of the spokes towards that tension. That usually throws the wheel out of true. Then I go around retruing the wheel checking tensions as I go – aiming for a true wheel with relatively even tensions.
Regarding the question above about the actual tension vs having balanced tensions, what matters most if the balance – that is what creates a stable structure. The actual tension value seems to be a ±10 or even ±20 percent thing (based on the specs of good tensiometers and a post Park's site called Wheel Tension Measurement). Based on my limited experience with the iPhone app you can match tensions very closely (±1 count).
If you are not sure about the calibration of your tensiometer I would think that you could get close to a decent number by having someone of similar weight to the user of the wheel sit on the bike with the wheel mounted. This will load the wheel and you can check spoke tension under load. You don't want to see a change in tension.
Having the book is one thing... Jobst Brandt's genius makes the mathematical facts very clear if you read it carefully. Here's my book report:
You wouldn't affect tension by weight-loading a completed wheel, except specifically at and near the very bottom of the wheel, where the earth's surface pushes upwardly through the [pretensioned] spokes to hold up the hub on a 'virtual pillar'. The book includes a reference to a proof that no other static forces arise (other than what would normally arise within an equivalent rigid body performing the same function) in radially, at the axle, weight-loading a completed (fully tensioned) wheel. The spoke(s) at the bottom (or other point of radial force loading) area will experience a net/total tension reduction similar to (there's some trigonometry involved) the magnitude of force acting downwardly (in the static scenario) through the axle (which includes most of the wheel's weight). The profile of spoke-wise distribution of tension reduction will be a complex function of tire, inflation, rim rigidity, and residual stress (such as within a rim that would not be true if unlaced).
It can be thought of as being analogous to placing a heavy object directly on the center of a stable arch. In fact it literally IS doing this, only 'upside-down' from 'convention', because the rim is an infinite arch, with its stability arising through circumferential compression. Instead of having its ends resting on the earth, its ends exist virtually and securely within an effectively rigid foundation (within its own frame of reference), which provides the hub as its interface point to your external frame of reference.
In this arch (your RIM) there is some inward flexure from the earth (or other source of inertia or impulse), however infinitesimal it may be, and it is this movement that tends to relax the bottom spoke(s) by pushing through them, the force submitted being equal to the total weight applied. Spoke elasticity (degree of stretching with tension) accounts for the inward rim displacement and provides a continuum (wherein a spoke's tension is reduced along with its length, to a given degree [without instantly going slack]). It is this cyclic length change that induces spoke fatigue (along with that arising from driving and hub-braking forces, which provide equal-and-opposite tensile actions in respective leading and trailing spokes).
If there is one most load-affected spoke, it would be the one closest to the point of bearing contact on the 'riding' surface. The load-carrying capacity of the wheel is strictly limited by the tension of the least-tensioned spoke in this way, because the stability of the wheel may be lost when a spoke goes fully slack, as the rim is then left on its own to bear whatever residual (a quantity of the applied force having been 'consumed' by slacking the spoke(s)) static or transient load is presented.
Bottom line, make a wheel TIGHT enough and TRUE enough, and you will not need to be concerned with relative tension. If you are, it is almost certainly the rim's fault.
Much of this has been paraphrased from my own copy of the book, which I have carefully read, and which I put to practice with 100% flawless results (notwithstanding a wrench-stripped nipple during a build here and there because of inadequate lubrication).
