# Park TM-1 tension-meter accuracy



## dcgriz (Feb 13, 2011)

Let me first say that good wheel building does not rely on the use of a tension meter. Wheel builders have been relying on the tensioned spoke tone consistency for ages and excellent wheels have been built by plucking the spokes and listening to the tone they make.

Personally, I prefer using the meter to arrive to equal spoke tensions (relative tension) around the wheel and also know when my tension goal has been reached (absolute tension). 

I do find the TM-1 capable of adequate repeatability, essential to determining the relative tension between spokes. My meter shows a deviation of no more than 5kgf which is further reduced to within 3kgf by the uniformity of the squeezing action (hard squeeze vs. soft squeeze + tap). Overall, pretty decent on that end.

Where I find the meter to be off is the absolute tension measurement and the point of the thread is to best avoid using it for such purposes unless the meter is calibrated for the particular spoke in use. Calibrating the meter is really a very simple process involving hanging the spoke, apply a known weight, use the meter to read the spoke tension and compare the listed mass (force)with the actual mass. Its best to calibrate the meter for each spoke type and even for each spoke batch. Doing so I found my meter reading tensions 19kgf higher than the actual value when calibrated against 14/15/14 ga. Sapim spokes (graduation #23 actually corresponds to 111kg rather than the charted 130kg). This is a substantial difference that could result in insufficient tension if not properly accounted for.


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## Mike T. (Feb 3, 2004)

dcgriz said:


> Let me first say that good wheel building does not rely on the use of a tension meter. Wheel builders have been relying on the tensioned spoke tone consistency for ages and excellent wheels have been built by plucking the spokes and listening to the tone they make.
> Personally, I prefer using the meter to arrive to equal spoke tensions (relative tension) around the wheel.


Using a tension meter to gauge relative tensions seems very laborious to me. I don't know about you but when I'm removing a wobble I first judge how big it is (large? small?) and then decide how many spokes I'm going to loosen (between 1 & 5?) how many I'm going to tighten (between 1 & 5?). Now, rather than giving them all the same fraction of a turn, I pluck them all. If a spoke is a lower or higher tone than its neighbor, it gets more or less of a turn, depending on its tone. What's the point in tightening a spoke a 1/2 turn if the ones on either side of it are already at a lower tone (lower tension)? Then maybe it needs a 1/4 turn and others a 1/2 and they will all then be at the same tone (and therefore tension).

This is done as fast as you can think. To do this with a tension meter would take great gobs of time, if ever done at all.

If I had a tension meter (and I don't) I would only use it for a final check on *one* spoke - just to make sure I was at an acceptable level of tension. 

If a person doesn't have a good ear for tone (and I think everyone is really better than they think they are) a simple <<$10>> guitar tuner, clamped to the wheel stand, is an incredibly accurate gauge. Google Image "clip on guitar tuner" if anyone doesn't know what I mean. Just leave it clipped on and turned on for the whole wheel tensioning/truing session. Pluck three spokes as quick as a flash, watch the LCD "needle" and decide how much less (or more) each spoke needs than the others.


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## dcgriz (Feb 13, 2011)

When I wrote the opening post I feared this would turn into a tensionmeter vs. plucking debate which it's not the purpose of the thread. However, since you brought these points up, here's my take on these......

Plucking the spokes and adjusting tension to same tone will eventually bring the equilibrium you are after. Some times it takes longer than others depending how far apart you are, what incremental steps you took and how good you are . What I don't like about this process is that you don't know at what tension you are at the time. You have the high tones and the low tones, you know you are apart but don't really know how far or how close. You apply tensioning or detensioning at small increments and through plucking, trial and error you may arrive at your goal. So, at the end, your spokes may sound the same which means they are at the same tension range and now you enter in the next phase and more questions.

What are the limits of this range and what is the actual tension you spokes are at? How a spoke sounds at 110kgf vs. 115kgf? These are the questions that personally bother me with the plucking method. If relative tension between spokes was all I was looking for then plucking may have been adequate but what about absolute tension? When do I know I have arrived at my desired tension if I don't have a wheel I trust next to me to compare the sound of the wheel I am building to the sound of that wheel? Some say to judge whether you arrived at max tension based on the resulting rim deformation and then backing off; I don't like reaching that far.

I also believe that some builds are more conducive to plucking than others. If one builds using a lot of heavier spokes (ie 32 double butted 14/15/14 ga) tensions typically do not need to be higher than around 120kgf but if lighter and fewer spokes are used (ie 24 Lasers) then, IMO, you need to drive the tension higher (130kgf+) and would be best to know where you are.

I like using this utility for a visual on where the wheel is at a time. SpokeService :: Spoke tension
With the TM-1 you need to manually input the tensions but with the Wheelfanatyc could be done automatically. Nirvana!!! Santa-Claus are you listening?????

Mike , at the end of the day, we all use what we feel more comfortable with. I have used the plucking method to true a wheel that came out of true but when building a new wheel I prefer using the tension meters. The TM-1 is not overly accurate on absolute value measurements and thus the point of starting this thread because with just a little bit of work this meter could become an accurate measuring tool.


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## mikerp (Jul 24, 2011)

dcgriz said:


> With the TM-1 you need to manually input the tensions but with the Wheelfanatyc could be done automatically. Nirvana!!! Santa-Claus are you listening?????


My wife asked what I wanted for Xmas, I gave her a list of items on Amazon as well as a link to the Wheelfanatik tool. I'll pick up whatever she doesn't pick up.


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## Mike T. (Feb 3, 2004)

dcgriz said:


> When I wrote the opening post I feared this would turn into a tensionmeter vs. plucking debate which it's not the purpose of the thread.


Well, you did use the sentence - _"Personally, I prefer using the meter to arrive to equal spoke tensions (relative tension) around the wheel and also know when my tension goal has been reached (absolute tension)." _That _did_ leave a door open to someone with another way of arriving at the same place. IMO it actually *benefits* the Newbs. They now have two different methods and can decide which they would be more comfortable with.


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## dcgriz (Feb 13, 2011)

Mike T. said:


> Well, you did use the sentence - _"Personally, I prefer using the meter to arrive to equal spoke tensions (relative tension) around the wheel and also know when my tension goal has been reached (absolute tension)." _That _did_ leave a door open to someone with another way of arriving at the same place. IMO it actually *benefits* the Newbs. They now have two different methods and can decide which they would be more comfortable with.


No prob Mike. Knowledge is never hurtfull and definatelly there is more than one way to "skin the cat". The more one knows and understands the better off that person is and this is the underlying purpose of forums shuch as this.


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## dcgriz (Feb 13, 2011)

mikerp said:


> My wife asked what I wanted for Xmas, I gave her a list of items on Amazon as well as a link to the Wheelfanatik tool. I'll pick up whatever she doesn't pick up.


Plan B is to look at the mirror. There I see Santa-Claus all the time!!!


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## headloss (Mar 3, 2013)

Mike T. said:


> IMO it actually *benefits* the Newbs. They now have two different methods and can decide which they would be more comfortable with.


No way to empirically test this, but my gut tells me that the guitar tuner method is more likely to result in spokes being pulled through the rims. I can see where it is a useful tool if you already know what you are doing, in order to speed up the process. In fact, I love the idea of having a constant gauge that doesn't require attaching and reattaching, I can easily see why you like this method; but, it still should be verified by a calibrated tension meter and not be used with a guitar tuner alone. Personally, I think you are giving out bad advice suggesting that the newbs use this approach. Ruining a rim with too much tension is a heavy price to pay. I guess where we differ in opinion is that you don't think it is likely while I think it is.

I speak from personal experience. I discovered the tonal approach to wheel building a few years ago, before I really knew what I was doing. I did, in fact, ruin a rim when I was a newb (granted, it was a cheap rim with known problems and had already seen five years of use). The issue is having a good baseline, be it one spoke of a known tension or another identical wheel to compare with. If you have that baseline, then I'm all for the guitar tuner method. If you don't, proceed at your own risk.


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## Enoch562 (May 13, 2010)

I had doubts about the accuracy of my TM-1 and I wanted a to have a 100% accurate baseline so I bought a WheelFanatyk gauge to check my TM-1. My Park Tool had me building wheels about 5 KGF light, which is almost nothing. I was totally surprised when I started checking all my previous builds because I felt I was over tensioning some rims. 

I still like using the park tool because it is fast and easy to handle and I don't have to fear breaking it when I drop it. You do have to use a little common sense and finesse when using it. I do use my digital gauge to do final checks. It is important to me to know exactly where I am on tension. I used tone and feel for years also with very little issues. I believe in re dundant systems. Now I have 3 ways to tripple check myself.

FWIW, I checked my Park Tool against a friend of mine and we found his was 5 ticks, on thier scale(25 kgf), off from my TM-1 so not all of them are accurate.


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## dcgriz (Feb 13, 2011)

@enoch562 --- 5 kgf light is darn spot on for a tool like the TM-1. Mine is 19kgf light (when it reads the equivalent of 130 kgf it's really 111 kgf) so I have to resort to my own chart for the particular spokes I am using. On the bright side though, its repeatability its pretty good.


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## mikerp (Jul 24, 2011)

dcgriz said:


> its repeatability its pretty good.


Ultimately this is what it comes down to with the TM-1, and why it's worth using.
It's a great tool for what it does.


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## pushstart (Feb 5, 2012)

The frequency method has good science behind it. Apps like this will hopefully become increasingly easy to use: https://itunes.apple.com/us/app/spoke-tension-gauge/id518870820

In talking to the developer, one issue with the app is that on butted spokes it is hard to know exactly where to measure from (on nipple side). Obviously the length of the span between cross and rim is key for determining the tension based on frequency. He has had good results with measuring from halfway down the taper (i.e. before the thinner main part of the spoke). Incidentally, on doing research on the project he found a ~10% variation between the 5 or 6 TM-1 meters that he collected for cross-reference.

(The app like that for Android platform unfortunately doesn't work at all. I will borrow my wife's iPhone for my next build to cross-reference with the TM-1.)

The idea of calibrating the TM-1 for each spoke is intriguing. My TM-1 seems to have an alignment issue (or maybe technique flaw when I began using it) such that the metal rubs and has scraped the paint off the contacting edges. This makes my readings sticky; I will grease it and see if that helps more consistency between reads.

I also plan to rely on tone increasingly in my builds -- whether app-assisted or just doing it by ear.


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## Mike T. (Feb 3, 2004)

headloss said:


> No way to empirically test this, but my gut tells me that the guitar tuner method is more likely to result in spokes being pulled through the rims. I can see where it is a useful tool if you already know what you are doing, in order to speed up the process. In fact, I love the idea of having a constant gauge that doesn't require attaching and reattaching, I can easily see why you like this method; but, it still should be verified by a calibrated tension meter and not be used with a guitar tuner alone. Personally, I think you are giving out bad advice suggesting that the newbs use this approach. Ruining a rim with too much tension is a heavy price to pay. I guess where we differ in opinion is that you don't think it is likely while I think it is.
> I speak from personal experience. I discovered the tonal approach to wheel building a few years ago, before I really knew what I was doing. I did, in fact, ruin a rim when I was a newb (granted, it was a cheap rim with known problems and had already seen five years of use). The issue is having a good baseline, be it one spoke of a known tension or another identical wheel to compare with. If you have that baseline, then I'm all for the guitar tuner method. If you don't, proceed at your own risk.


I never said to use the guitar tuner or pluck/listen method for ultimate spoke tension. I stated that is is for relative tension. In fact it's almost the same info given out by Roger Musson in his fine e-book. I'll bet there are FAR more home-built wheels that *never* see a tension meter and they do just fine. IMO a person has to be very mechanically insensitive to "result in spokes being pulled through the rims." In all my years (12? 14?) of talking to newbs who build their first wheels from my site's info, I have yet to hear of *one* who suffered a nipple pull-through because of it. Not one. So "bad advice" isn't bourne out from my feedback. If it was, I would have stopped giving out the info years ago. Do you really think I would keep telling newbs to *not* use a tension meter if even *some* of them were complaining of nipple pull-through because of my advice. Gimmy a break.

I even mention on my site to compare tone to a known good wheel.


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## dcgriz (Feb 13, 2011)

pushstart said:


> The idea of calibrating the TM-1 for each spoke is intriguing. My TM-1 seems to have an alignment issue (or maybe technique flaw when I began using it) such that the metal rubs and has scraped the paint off the contacting edges. This makes my readings sticky; I will grease it and see if that helps more consistency between reads.
> .


I'd like to emphasize that my calibration of the TM-1 is strictly creating a new chart for it and specifically for the exact spoke type, make and weight. I am not altering or repositioning any part of the tool itself. 

If your meter sticks maybe some very gentle sanding may help it. I would be skeptical about using grease because doing so will always require the same degree of lubrication in order to read consistently. IMO, you want the tool surfaces to be dry.


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## headloss (Mar 3, 2013)

Mike T. said:


> I never said to use the guitar tuner or pluck/listen method for ultimate spoke tension. I stated that is is for relative tension...


OK, My bad. Now we are on the same page.


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## pushstart (Feb 5, 2012)

dcgriz said:


> I'd like to emphasize that my calibration of the TM-1 is strictly creating a new chart for it and specifically for the exact spoke type, make and weight. I am not altering or repositioning any part of the tool itself.
> 
> If your meter sticks maybe some very gentle sanding may help it. I would be skeptical about using grease because doing so will always require the same degree of lubrication in order to read consistently. IMO, you want the tool surfaces to be dry.


That's a good point about the grease. I was thinking that these surfaces probably shouldn't be rubbing at all. I try to release the lever in such a way that the surface contact is minimal, but it seems to want to scrape like scissor blades. I will try the sanding approach first to smooth that out.

Understood re calibration, thanks.


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## dcgriz (Feb 13, 2011)

pushstart said:


> Understood re calibration, thanks.


Park shows the following calibration procedure BUT proceed at your own risk.....if you do, keep count on how many turns you turn the adjusting screw so you could put it back to the factory setting if you change your mind.

From the Park website:
"Calibration
The TM-1 Tension Meter is calibrated at the Park Tool manufacturing facility. Generally we do not recommend readjustment of tool. If the tool is worn or damaged and appears to be inaccurate, return to Park Tool for recalibration. Park Tool will recalibrate and return the tool for a reasonable charge.

It is recommended for professional mechanics and service departments use a non-riding wheel to help in tool calibration. Remove the axle from a wheel so that it is not rideable. Mark a spoke as a reference spoke and measure this one spoke. Write the date of the measurement directly on the rim. This same spoke can be used to double check the original calibration. If the tool is reading different than this "reference spoke", the spring tension can be changed. If the tool is reading low, take the tool off the spoke and turn it upside down. Remove the spring from the fixed moving stud, and then thread the adjusting screw inward toward its stud. This will decrease tension on the TM-1 spring, resulting in a higher deflection reading. If the TM-1 is reading high, increase tension at the adjusting screw."


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## looigi (Nov 24, 2010)

FWIW: You can calibrate the device by attempting to adjust it or simply create a correction table that is applied to the indicated value to get a calibrated value.

With a TM1, that's basically the modus operandi anyway, as its indications are arbitrary until converted via the spoke table or spreadsheet they supply.


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## jnbrown (Dec 9, 2009)

I use a TM-1 and also use the tone method.
I think they both work but since I don't build very often I like to use the TM-1 to verify that my building by ear is accurate. At some point I felt the TM-1 was reading low which resulting in me making the spokes tighter than I thought they should be. I sent the TM-1 to Park to have it calibrated. They did not tell me the results and I don't feel much difference before and after it was calibrated.
You say it is simple to calibrate the meter by hanging the spoke with a known weight. So for 100Kg you would need to hang a single spoke with 220 lbs? How in the heck would you do this? I think having a reference wheel would be better that is calibrated with a high accuracy tensiometer.


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## dcgriz (Feb 13, 2011)

Creating a correction table to get a calibrated value is basically the "safe way" and what I have recommended on this thread. The following is the next step if you dont mind fiddling with your TM-1.

The ultimate calibration would be to adjust the adjusting screw on the backside of the TM-1 so you read the actual calibrated value. I have done this to mine but have been hesistant to suggest to others do it because of skewed results if the procedure they use to calibrate the TM-1 allows torsion to develop.

To elaborate: The principle of hanging the spoke, apply weight and measure the tension is simple in theory but it does require a due dilligence in practice. Care should be exercised so there is no twisting of the spoke by allowing the weight to swing freely. Equally important is how the head of the spoke is attached to the pulling weight; the attachment should not allow any bending and concentrate the pulling on the spoke head. The idea is to simulate how the spoke is attached to the rim and hub.

This is how I do it: 
- Find a suitable location next to an existing column to hang the spoke from: an I-beam supported by a lolly column in my basement was perfect for this
- Attach the spoke so it can rotate freely if twisting is applied: After threading the spoke through an existing 3/8" bored hole on the I-beam flange and a series of washers to reduce the opening, I screwed a nipple on the nipple threads. The nipple shoulders rest on the washers (selected to be slightly larger than the nipple neck) and allow the spoke to rotate freely on its threads so a twisting moment is not allowed to be built. 
- Attach the spoke head: Here you need to simulate how the hub flange attaches to the spoke using the same tolerances. You need a plate that has the approximate thickness of a hub flange and the same diameter hole as the flange for the spoke head to rest on. You also need to make certain that the spoke elbow does not bend when you apply the load. The backplate of a galvanized steel electrical junction box worked perfectly for this and also allowed a 1" punch-out hole on the opposite end. 
- Attach the weight: A clip attached to the 1" punch-out of the plate described above allowed a length of rope to go through and support a 2' length of a 2x4 suspended a few inches off the floor (like a swing). This is the base where to add the weight. In my case, the weight was me as I simply stepped onto the 2x4, supported myself from the adjacent column so I would not spin around (very important for the accuracy of the measurement) and took the measuremnts. 

This process has worked beautifully for me and is giving me the same exact reading time after time. My meter was reading high so the adjusting screw had to be turned inwards to apply more pressure to the tool's spring; it took 5 full turns on my TM-1 to make the chart correspond to the actual weight applied for a Sapim Race.

I should also note that since the TM-1 is sensitive to the thickness and type of spoke and it's behavior is not exactly linear across the weight range, IMO, it's best to calibrate the tool for the exact same spoke you plan of using and apply enough weight to reach your goal tension weight (i.e 125 kgf) so extrapolation is not needed. I think you will be pleased with the results 
(and may be amazed from how much weight this spoke-nipple combo can withstand).


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## dcgriz (Feb 13, 2011)

jnbrown said:


> You say it is simple to calibrate the meter by hanging the spoke with a known weight. So for 100Kg you would need to hang a single spoke with 220 lbs? How in the heck would you do this? I think having a reference wheel would be better that is calibrated with a high accuracy tensiometer.


Having a reference would work if it stays the same (not riding the wheel) and if it uses the same spoke as you plan of using. 

If you choose to follow my approach then attach burbells on either side of the 2x4 I mentioned on the previous thread to compliment and add to your weight until you reach your target. If you are 190lbs it would be easier than if you are 140 lbs but it could be done either way (just be carefull how much weight you add at the ends of the 2x4.)


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## coachboyd (Jan 13, 2008)

jnbrown said:


> You say it is simple to calibrate the meter by hanging the spoke with a known weight. So for 100Kg you would need to hang a single spoke with 220 lbs? How in the heck would you do this? I think having a reference wheel would be better that is calibrated with a high accuracy tensiometer.


This is how we did it. The spoke in the picture has 118.0KgF on it. . .so when we check our tension meters (multiple times per day) we know that they are accurate.









This was a fun little project to build, S-Beam load cell, digital indicator, and some parts from Home Depot. I think I spent about $120 total on this.


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## dcgriz (Feb 13, 2011)

coachboyd said:


> This is how we did it. The spoke in the picture has 118.0KgF on it. . .so when we check our tension meters (multiple times per day) we know that they are accurate.
> 
> 
> 
> ...


That's pretty good. I bet if you market it, there will be buyers.

Mine is very crude compared to yours but it works and for what it costed me (nothing other than the stuff I scavenged looking around my workroom) it turned out pretty good.


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## mikerp (Jul 24, 2011)

Nice little project 
Thanks for sharing.


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## .je (Aug 25, 2012)

Just for snits and giggles, has anyone tried out a spoke tension meter for their smartphone, like these?
Check Spoke https://play.google.com/store/apps/details?id=jp.gr.java_conf.MagokoroStudio.checkspoke
Spoke Tension Meter https://itunes.apple.com/us/app/spoke-tension-gauge/id518870820?mt=8


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## pushstart (Feb 5, 2012)

.je said:


> Just for snits and giggles, has anyone tried out a spoke tension meter for their smartphone, like these?
> Check Spoke https://play.google.com/store/apps/details?id=jp.gr.java_conf.MagokoroStudio.checkspoke
> Spoke Tension Meter https://itunes.apple.com/us/app/spoke-tension-gauge/id518870820?mt=8


Yeah, I mentioned the iPhone one a few posts back. I haven't used it, but I know the developer (and he uses it for builds). It should be more accurate / reliable than a deflection meter, but obviously measuring is important (and as I alluded in previous post there is a bit of a challenge with length measurements of butted spokes).

I tried Check Spoke and it does not appear to work at all, or at least it didn't produce any repeatable numbers when I was testing it. I emailed developer and got no response. Maybe too much background noise. I will borrow my wife's iphone for my next build to see whether the iPhone app is helpful (in conjunction with my TM-1).


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## changingleaf (Aug 20, 2009)

The TM-1 is a fairly user friendly device, but can very inaccurate. I definitely recommend hanging a spoke on a weight or using a load cell to test absolute tension measurement. Using sound for tension is a great and tool for quickly brining a wheel to tension. I have found that truing primarily from the radius of the rim and using spoke pitch to be very quick and accurate. The wheel Fanatyk meter with the digital SPC output cable is very useful for recording final tension for quality control. Reaching the correct tension is very important in order build a long lasting wheel especially when building with lightweight rims. Lighter riders do not necessary need a rim's max spoke tension to have a quality build. Some rims can not handle the tension necessary for larger riders because they have a spoke bed that is too thin. Regardless, building all rims to the same tension for each rider is usually better. More spokes and a heavier rim is a better choice for a larger riders than stronger spokes and more tension.


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