Using a Spoke Tensiometer
 

Food for thought.

Some time ago I wrote a program to calculate spoke lengths and it did the job but I also went and included something that gave the predicted spoke tensions based on the shortest spoke having the highest tension picking 130Kg as a base figure.

Recently I tacoed the wheels I had previously built. When I had finished them they did seem a bit tight when plucked but over time despite using stainless Alpina butted spokes they had become speckled by rust so time to build some new ones.

This time I invested in a Park Tools TM-1 and took the tension figures from the program as an initial target then laced the wheels to the point that the threads were just disappearing into the nipples then went around bringing the wheel up to tension.

When I had something stiff but not too stiff I worked around gradually bringing each spoke up to the tension suggested by the program.

In the front wheel this was,

Outer Right 113
Inner Right 130
Inner Left 130
Outer Left 113

In the rear wheel this was,

Outer Right 102
Inner Right 130
Inner Left 78
Outer Left 67

Whilst doing this every so often I worked around the pairs of spokes giving them a firm squeeze. When I had finished both wheels were basically true but needed some minor horizontal adjustment to true them fully. I should mention that this was with new rims and spokes.

Since a bad workman always blames their tools I will mention that the TM-1 seems to suffer from backlash so I had to make multiple squeezes on the tool to settle to a particular value. Also the relative precision or accuracy of the reading might be in doubt.

However given the marked different tensions as indicated by the program it seemed that the tool would give a good initial indication of the targets. At the end of the day, on a sample of two wheels, it would seem that the method used appears to work quite well.

Thoughts?

I've never noticed a difference between the leading & trailing spokes, only between the drive side & non-drive side. A difference in torque between leading & trailing spokes would/should cause wheel rotation. So, it makes sense that the tension in a static state would be equal.

Getting good measurements between leading/trailing can be a bit more trying though with the cross causing interference with the measuring tool.

When I use the tension meter I make sure it doesn't touch a cross or engage across any transitional area of any butting & give it a little wiggle to settle any lashing within the tool itself. This should seem obvious but, Hey! It's the internet.

Though I spend the majority of my time focusing on the wheels roundness, the tension meters most useful function (to me) is to tell me which spoke is the one confounding the works; which spoke is doing more than it's fair share so that it can be released & the load shared by it's neighbors. But, it is also useful for approaching the upper limit of the rims designed tension range.

I think the problem with blindly tensioning to a preset value determined by a computer program is that you are looking at a spoke as if it were a discrete component & not part of a system. It is very possible to make a perfectly tensioned an offset/egg/potato chip hybrid going by spoke tension alone.

.
...the TM-1 is not designed or intended as a precision tool. But it works well enough for most wheel building applications.
When I was doing more wheel work, I invested in one of those fancy Schmancy tension meters,, that cost more.

https://cimg4.ibsrv.net/gimg/bikefor...9cc5919dbe.jpg


I still use a Park meter for most of what I do on wheels now, because I stuck the other one up on a shelf, and it's harder to get to. :o
I just googled the Hozan dial indicator spoke meter, and they are up to 500 bucks now. I guess it's worth it if you build a lot of wheels, but that's a substantial investment.

There is an Excel file for tensioning spokes. The pain is the entry of the values. It generates a nice spider diagram of tension that is interesting.

The instructions state tension for all spokes should be within 20% of each other. That is a lot of margin. If it works, great.

130 kgf sounds high to me. Are you sure your rims and hubs can handle that much of a load? I normally aim for 110 +/- 10 kgf for front and drive-side rear spokes.

^This^ I'd shoot for getting all DS spokes at the same tension regardless of whether they're pulling or trailing. If you get them to the proper tension for the particular rim/spoke combination you have and the rim is centered/round/true you're done. The NDS will be whatever it will be, no need to check it. 130lgf is most likely too high for any rim.

My Park TM-1 read 30% low out of the box. I didn’t realize it until I started cracking rims. Even after returning to Park for recalibration, it was still off. I ended up jury rigging my own calibrator to make sure I had the right tension for the spokes I was using. My experience may be an outlier, but just a word of caution.

I shoot for a minimum of 65 kgf on the NDS and not to exceed 120 KGF on the DS.
If I can't do that, get a different hub or offset rim.

I used my TM-1 only to get the spokes within reasonable range and roundness. Once there I'd true the wheel without it and check again. If that last check was still reasonable I'd let it be. If I found some real outliers I'd tweak them to get back within range but even a 30% outlier was probably a better bet than trying to get them even only to have something else get out of whack. I haven't used it in a few years now as I'm done building wheels.

None of the wheels I've ever built for myself have given me any trouble and I ride in NYC. The roads aren't exactly the smoothest around. I think the last broken spoke I had was on a wheel I hadn't built myself. I went and rebuilt that one too and haven't touched it in at least 5 years if not more.

It must be really nice to be able to actually know what the tension is on your spokes. My little knockoff ChiCom spoke tension tool is a very use full tool for me. I use it allot when balancing out my wheels and thier true.

But really, I don't believe any of the numbers on it as being accurate. I guess I should care about this more...

Well, I would check it just to make them even. When truing, I will come upon neighboring spokes (of the same side) which are quite a bit off from each other, and I know balancing them will not affect the trueness (at least not enough to matter more than even spoke tension). But yes, the average of the NDS will be whatever it needs to be in order to properly dish the wheel.

It doesn't hurt to check it, when I'm building a wheel I don't because of how I add tension. If I'm tensioning and my wheel isn't round and straight I can be pretty sure I started with a bent rim. Not usually an issue w/ carbon rims, definitely can happen w/ aluminum rims. When truing a wheel that someone has brought in to the shop I might check them at some point just so I know what's going on a little more precisely but normally not. I'm going to check the drive side for sure. If I get those tensions really even and the wheel is still out (and the NDS isn't obviously all over the place) I know the rim is bent. If I start running in to this I'll contact the customer and let them know their options: A wheel rebuild OR a wheel that's reasonably straight and round but won't stay that way for too long.

Not a criticism, but simply a jumping off point.

It is entirely possible, and all to easy to build a wheel with tension differences between pulling and trailing spokes.

Naturally, having all pulling spokes having more or less tension than all trailing spokes can't happen. However consider a wheel where pulling spokes are tighter on one flange, and looser on the other.

The wheel as a whole is in static equilibrium, but the flanges are being torqued in opposite directions, with the rigidity of the hub shell preventing them moving to neutral tension.

In this scenario, you'd get tensions similar to the Hi-Lo pattern in the OP's wheel. I can't say for sure about his because he didn't reference pulling or trailing.

FWIW back in the bronze age when I was in retail, someone brought a wheel that he was struggling with because half the spokes ran out of threads. The wheel was so tight the shell couldn't resist the torque, and the Campagnolo logo in the middle was helical.

The secret to a good wheel build lies in the process, wherein you don't introduce uneven tension, except as needed in final truing. Focus on maintaining even LENGTH and the tension takes care of itself. Then, if you prefer, you can use an instrument as a QC device.

I have a Park TM-1 and a Wheel Fanatyk tensiometer. I use the WF tool to check that spoke tensions are somewhat close to each other. I never got very consistent readings from the TM-1 and gave up on it pretty quickly.

FWIW, over the years I’ve become less concerned about building to specific spoke tension numbers than about building straight, round wheels. I have wheels that I built years ago and rode for multiple seasons and many miles. After I got the Wheel Fanatyk tool I tested a few of them and was surprised to see that none of the front wheels, or non drive side spokes on the rear wheels, were above 90 kgf or so. Maybe that was a good number back then and spoke tensions are higher now given that the rims are stronger. Beats me; all I know is that I rode some of those wheels all season and they never even got out of true.

And those wheels did not have an easy time of it. Back in the day I was a big strong guy; now I’m just a fat old man. Of course, those older wheels all had 36 spokes. I still believe in higher spoke counts than are currently fashionable, but that’s a rant for another day.

The tools that are really useful to me these days, as I have a fair amount of arthritis in my hands, are spoke driver bits that fit on a power screwdriver or drill. These are made to tighten each spoke nipple by approximately the same amount and will get a wheel to a reasonable starting point for tensioning and truing; they’re not perfect by any means, but tensioning and truing get a lot easier when you have a decent starting point. I find that these help me get to where I can tension a wheel pretty quickly and concentrate on getting it true and evening out the tension between spokes — which is typically less of a problem given a good starting point.

I have done just the opposite (I used to be proud that the wheels only made a sound when the seam of the rim went by), and it's because the extreme dishing and desires for lightweight rims made such a wide variation between the two sides that you needed to run the drive side up the the brink of "too tight" and the non-drive side just barely past "too loose". A long time ago, I had a rim fail, quite possibly due to too much tension. The resulting crash made me decide that it's better to have the spokes too loose (spokes break) than too tight (rim breaks), and used the tension tool to make sure.

I don't have much faith in the Parks TM-1, or that design of a tension meter in general.

Rather than repeating some previous thoughts/work:

https://www.bikeforums.net/bicycle-m...on-meters.html

Good point. Lately most of the wheels I’ve built are leisure/touring/gravel wheels, so I haven’t seen anything you would characterize as a “lightweight” rim. Mostly CR-18s for budget builds, Velocity Dyads, some Chukkers, and stuff like that. Probably the lightest pair that have crossed the bench lately are H Plus Son Archetype, which are 470 gram and have a decently thick spoke bed. I’d probably have a different perspective if I built a lot of lightweight race wheels, but those days are long past.

Me too, I've got a knock off tension meter (Ztto TC-1).
I set up a very similar arrangement to check its calibration.
Then I fitted an exponential curve to convert the reading to actual tension KgF

A thing I noticed is to bounce the tension meter against the spokes until the reading settles down.
Friction in the mechanism means it can go down about 0.5 or more.

Used it to relace some Mavic Monthlery Route and MA2 with max 90KgF.
Now about 1k miles later and no issues.

Apologies for the bump and also apologies for not responding to the most excellent replies. In particular the concern about differential torsion applied to the hub. That one really made me wonder to the extent that I set them aside.

The counter argument, for which I may perhaps be slaughtered, is that we know that for a dished wheel the spokes closest, shortest, to the rim have a higher tension. Drive side has a higher tension than the non-drive side. By extension on each particular flange the spokes exiting internally will, should, have a higher tension than those exiting externally. At least in a lateral sense.

This is not to say that you cannot get a valid answer by assuming that the tension either side in isolation can be set up as being equal and you will end up with a true wheel. It is saying that the difference is there and by adopting that difference you can end up with an equally true wheel.

This is what I got, on new rims, using my Park Tool adopting those differences. A true wheel. Of course as others have mentioned and as I noted myself the tool might not be overly accurate but measuring twice, more, it gets a relative answer.

However the proviso might be that my program basis its suggested tension solely on the lateral angle of the spokes. The smaller the lateral angle the greater the tension. In number terms it is a significant difference, 10kgf non drive vs 26kgf drive, but in real terms it may not matter.

In respect of torsional forces as opposed to lateral ones I am going to take an uneducated guess based on a wet finger and the method of it seems right in my head that leading and trailing spokes operate in the same direction either side of the hub, the twist makes it so, and therefore the differential tension in a lateral sense extends to the torsional sense and the hub will experience or adjust to the same twist/torsion on each side and remain balanced.

Having convinced myself that this is the case I shall make the last few tweaks and stick rubber on them, put them on the bike and see if I taco face plant myself.

Again. Thanks for the comments and other information.

1. Each pairs of spokes on each side in a typical built wheel has two offsets. The difference will be 3.2mm - the typical thickness of an alloy hub. Given the same balanced nipple turn treatment, they will have a tendency to show different readings.

This is why after the initial tensioning of a wheel, I do a tension balancing treatment of each side of the wheel before continuing - to try to get ahead of this. I'll do it again later on in the build.


2. The TM-1 is a cheap budget tool. It works...sometimes it slips or as you metioned - "backlash". But so long as you keep it calibrated - roughly every dozen wheels - it works just fine.

3. All tension meters give estimates - NOT a precise or accurate reading.

Hence why I tell customers something like: "Drive side tension is between 95 kgf and 107 kgf."


4. Best us of a tension meter - calibrated or not - is to check relative tension.

That's how you verify that one noodle you see popping in or out while the wheel is spinning is not with the program.

I have a very old TM-1 that is set with a new version TM-1 spring. It simply cannot be calibrated according to the charts. So I just use it to check relative tension.

So word to the wise - don't toss out old tension meters. They still have other uses.

=8-|

This thread illustrates the difference between knowledge and wisdom. Or more to the point, chasing data points vs. understanding wheels as a system.

2 observations.

There's discussion of the effect of flange thickness on spoke tension. That's moot because it's not a factor.

It's true that relative spoke tension relates to the angle that the spokes leave the rim, but the hub flange is out of it because the spokes are laced over/under. Therefore both inner and outer angles are different only according to the thickness of the spokes.
.........
As to torsional differences. While tension differences on individual spokes are possible, the sum of all torques will ALWAYS equal zero. The ONLY way to have differences between pulling and trailing spoke groups is to have one flange have a net torque in one direction, and the other flange have an opposite and equal net torque.

I have a TM-1 that I have used for many years and have built maybe a dozen wheels with it. I have not had any problems with those wheels. I am about to build my first set of carbon clinchers and became concerned about the accuracy of the TM-1 being that the pair of rims cost $460. So I built a calibration jig to check it. It is pretty accurate when measuring a bladed spoke like a CX-Ray but is reading about 20% high on round spokes.
so there is a good chance some of my wheels are under tensioned. I am glad I built the jig, it will give more confidence going forward.

1. There's radial with head out, and radial heads in. Try it sometimes - the 3.2mm offset difference will show.

2. The spokes laced / under over are heading out at 2x, 3x or 4x. The actual reach difference will only be at or less than .3mm. ( point three mm) Nothing to phone home about.

...and FB...all else considered equal - perfect rim set, perfect nipple set - there will be initial tension differences between the inside / outside spokes of a pair. The gap closes as the tension increases - but not 100%.

We're talking differences of less than 10 kgf for a 110-130 kgf wheel. Nothing to phone home about.

It's like arguing about inside pulling and outside pulling - instead of the just building the damn wheel.

=8-|

100 lb load on a suspended wire of a given gauge is a 100 lb load.

When you change the wire of a given gauge . . .

. . . the 100 lb load is still a 100 lb load.

Keywords = given gauge

=8-|

Yes, this is what I aim for as well.