Perplexed - Spoke width/tension
 

I have a self-built wheelset in which the rear NDS spokes keep loosening. It has a Velocity A23 rim, DTS Competition spokes on DS, and DTS Revolution spokes NDS. 28 spokes.

I was pretty anal about getting the trueness and tension perfect when I built them a few months ago. While retensioning them last night I measured the spoke width to make sure I know where to look on the Park TM-1 tension chart to get DS spoke tension up in the 120-130 Nm range. My Park DC-1 digital calipers report the DS spokes at 2.2mm in the center (2.4mm at each end). The NDS spokes 1.9mm in the center and 2.4mm at the ends. I thought the Revolutions only came in 2.0/1.5 & 1.8/1.5, and the Competitions only came in 2.0/1.8 & 1.8/1.6. The chart doesn't even have a line for 1.9, 2.2, or 2.4. Now I have no idea where to look on the tension chart to get the right tension.

Are these bizarre spokes?
Am I measuring them wrong?
Is my caliper wrong?
What am I missing?

I'm perplexed! Any help is greatly appreciated!

That is a reason why I think the Park spoke tension meter is not a good design for true force measurements, since measurements are affected (and accordingly have to be corrected) by spoke thickness. Another spoke tension meter (such as the one designed by Jobst Brandt, which has been produced by FSA) has a much more intelligent design of supporting the spoke and measuring spoke deflection under load from the same side (and not as the Park tensionmeter from the pressure side), which makes this device mostly independent from spoke thickness. For full discussion of technical aspects see also http://yarchive.net/bike/tensiometer.html

Yeah, those numbers don't sound right at all.

Digital verniers need zeroing, you know...

The TM-1 comes with a little metal gauge with multiple slots for measuring the diameter of spokes.

Digital vernier is an oxymoron!
There's-
Vernier calipers
Dial Calipers
Digital calipers

http://www.tpub.com/math1/7e.htm

perhaps French should be used for both terms, rather than just 1.

Did you even read the OP's question?

=8-)

Just like in the old days when I was told to use spark plug gap tools to set the gap on spark plugs - not feeler guages - use the included TM-1 tool or built in guage tools often available on spoke rulers.

Those allow for the acceptable range required to "meet" a guage - and remember as well that a tension meter is providing individual and whole wheel average tension ESTIMATES - not an exact reading.

In other words, don't lose sleep over it.

=8-)

caliper is wrong

Ah, forgot about that thing. Looks like the Revolutions fit easily in the "1.5" slot and the Competitions fit snugly in the "1.7" slot. Yep, those are the lines on the chart that I used when building the wheel. So now I have a mystery issue of spokes loosening within 100 miles despite excellent tension and meticulous attention to detail on all aspects of the build (spoke prep, lubing spoke holes, stressing, good tension, etc.)



I zero it out every use.



I wouldn't except it develops nasty loud pings & twangs after just 100 miles or so and I've had to re-true/retension it three times in the last few weeks. I'm fine with a little tension imbalance if it doesn't impact the ride and durability. This impacts the ride and durability.



I'll compare it to a friend's calipers this weekend.

Dear perplexed,

What is "excellent tension?"...............I'm assuming you know about and have dealt with
spoke wind up and rechecked your tensions after your tires were mounted and inflated.

120-130 newton meters ought to be good for just about every use I can think of,
but I'm curious, too about the spoke count in your chosen wheels ? If you're cheating
on the low spokage side of wheel building, you might require higher tensions for a
workable wheel.................

Oops, I see it now.......28 spokes. At considerable risk of bringing down a torrent of
abuse on myself, I'd suggest higher tensions for 28 spoke wheels. I use the tensions
you've mentioned for 36 spoke wheels, and you have 8 spokes less than that....but
I weigh in at 235, so I need to overbuild a little.:o

It's hard to measure spokes with a caliper, which is why the little go/no go gauge is
such a blessing.

120-130Nm on all DS spokes and NDS spokes all within a few Nm of each other.



Yes

If you get to the point where everything else checks out, I've had
reason to use green loctite...I forget the number, but it's used post
assembly because it wicks into the joint.

I've had maybe one or two wheels that did this over the years and
on one the loctite helped........don't know why or how.

Pardon my ignorance, but isn't Newton meter a measure of torque and not tension? How do you measure that on a spoke?

Standing corrected.

Buy a better one? Or ditch digital - not much can go wrong with a mechanical one ;)

All calipers, vernier, dial and electronic share a common problem in that they're dependent on decent touch of the user. For rough readings this touch doesn't matter, but if good precision is wanted differences in touch is critical for consistent accurate measurements.

The best way to check a caliper isn't to close it on itself because dirt or or damage at the tip can cause a false zero. Instead check caliper aainst a known standard like a 1/4" ball bearing, or something like piano wire which is very accurate. If you need to zero out an electronic caliper close it onto a piece of paper or dollar bill, slide it out under a bit of pressure to wipe the faces, close the caliper and reset the zero, then confirm on your standard. Unless correctly zeroed out and confirmed an electronic caliper is less accurate than just about anything, especially because if gives wrong measurements with the authority of a digital readout.

Like most tools, calipers in the hands of folks who don't know how to use them are just slightly better than useless.

Tricks of the trade by the dozen, get your tricks here, roll up :)

Sorry, KgF...........I got pretty drunk at the Joan Jett concert last night at CalExpo.:o

Didn't get me backstage with Joan Jett, but what the hell.....:love:

I stayed off this thread because the OP indicated too many potential issues, many of which could be lack of knowledge or experience. I'm still not confident of the OP's skills, but the first step would be to determine what's really happening. Are nipples unscrewing, spokes stretching, or simply settling because the elbows weren't set properly to begin with?

Nipple twist is easiest to confirm, by using a dry marker to make a reference dot on every NDS nipple, and checking for movement later on. Likewise spoke twist can be detected the same way with a dot on each spoke at the nipple.

Otherwise, the OP may simply have neglected to set the elbows which are slowly yielding, effectively lengthening (slackening) the spokes. This usually happens only once or twice, then time and rework achieves what should have been done during the build.

Another possibility is excess tension, causing rim settling at the spoke holes, but this usually happens on the right side before the left.

There are other possibilities, but until the OP resolves or eliminates the obvious there's no point in looking farther.

WTF? Who was in the band, Encino Man and some Egyptian mummies? :p

Every time I hear the symptoms spelled out by the OP:

1. Pings and twangs...
2. Spokes coming loose...

My brain throws out three things:

1. Did the OP stress relieve the wheels repeatedly during the building process.
2. Did the OP actually achieve the stated tensions.
3. And related to #2, is the OP using a calibrated tension meter.

=8-)

To a 60 year old guy like me, she still looks hot in a black jumpsuit, Bubba.................:o

Hey, us Gen-Xers are getting long in the tooth too, you know.

If Joan Jett were to crack on to me in candlelight, and I was doing an E...

I've been using the same spokes on the wheels I ride but 32 in the back and 28, all Revolutions in the front.
Take my comments for what they are worth, hope they help.
I cannot put nearly enough tension in Revolutions unless I lube the threads and hold the spokes with pliers. This way I get no spoke windup. Actually I also hold the Competitions with pliers too.
If I run more than 115 - 120 kgf on the drive side rear the spoke will "wallow out" the spoke holes in my 240s aluminum hub flanges. This puts the rear non drive side Revolution spokes in the 65 to 75 kgf range. (I use the Park TM 1.)
My spoke tension drop about 5 - 7% after inflating the tire and tube to riding pressure so I set tension based on riding conditions.
A few years ago I was running higher tensions and pulled a 2 inch section of flange right off the hub. The wheel was 6 years old. This would not have happened with a steel hub but I prefer aluminum. Since this hub failure I've lowered the spoke tension a bit.

[QUOTE=blaronn;14537853]Ah, forgot about that thing. Looks like the Revolutions fit easily in the "1.5" slot and the Competitions fit snugly in the "1.7" slot. Yep, those are the lines on the chart that I used when building the wheel. So now I have a mystery issue of spokes loosening within 100 miles despite excellent tension and meticulous attention to detail on all aspects of the build (spoke prep, lubing spoke holes, stressing, good tension, etc.)

DT Competitions are listed in the DTSwiss tech data as having a diameter or either 1.6 or 1.8mm in the center section of the spoke. Since your spoke fit "snugly" into the 1.7mm slot of the gauge, it seems the spokes you have are really 1.8mm dia.

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