Spoke Tension Meters

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Pebble
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Joined: 7 Jun 2020, 11:59pm

Spoke Tension Meters

Post by Pebble »

Recently bought myself a spoke tension meter to help me with my first wheel build. Unfortunately the meter arrived without a 'comparison table' As such I am unable to calculate the exact forces.

I have found elsewhere on the internet a company selling a meter that looks the same
https://pt.aliexpress.com/item/4000121647366.html
Apart from the name on the tool, what I have seems pretty identical, the web site also shows an image of a table (extract below) What do you think the chances are that the table for mine would be the same ? Do the numbers seem sensible.

Image

This table would suggest that a reading of 32 on a 1.8mm spoke would be 160kgf this seems a very high figure, this would be the equivalent of 25 stone hanging on a spoke (would a nipple really take that sort of load. (some of the spokes on my drive side are at 32 (which is the same as the wheel I copied)
If there is 160kgf on a spoke at rest, what sort of forces will be experienced on a drive spoke when working hard out of the saddle on steep ground? or hitting a pot hole (although I guess these forces will be shared)

Am I correct in thinking that a force 100kgf is as simple and straight forward as a 100kg weight being hung off a spoke? I'm thinking of calibrating my own tool or at least checking that the table I found online is relevant to my own meter.
Brucey
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Re: Spoke Tension Meters

Post by Brucey »

half-decent 14G spokes take 250kgf before they are likely to actually break.

IMHO in this situation the only way you can be remotely confident of the actual spoke tension is to calibrate the meter (eg using dead weights). Ideally you should calibrate the meter using the correct type of spoke and the correct tensions (dead weight(s)) too.

You can get an approximation by comparing with a 'known good' tension meter. But this (using another -probably un- or badly- calibrated meter as a 'secondary standard') is likely to be little better than guessing, frankly, given the nature of the beast.

The best tension meters are of questionable value; cheap ones with no calibration.... well lets just say 'a lot less than that'.

cheers
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TheBomber
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Re: Spoke Tension Meters

Post by TheBomber »

What claims were made about the abilities of the meter when you bought it - as without the calibration table many are likely to be false, giving you grounds to return it? Obviously the table is not required for getting even tension.

I was recently given the Park one (with its calibration table) but unless I’ve been building wheels with far too much tension for years it’s not accurate anyway. I’m tempted to build one of these as a lockdown project:

https://forum.cyclinguk.org/viewtopic.php?f=5&t=136484&p=1464360&hilit=Spoke+tension#p1464360

But I can understand that might be a step too far for a first wheel build.
mercalia
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Re: Spoke Tension Meters

Post by mercalia »

if not too late I would send the "meter" back as without a table it is useless?

I only use my Park tool for getting similar tensions rather than known tensions. Then such a device is useful. I know some people can do that by ear and when they are similar you can hear it, but its a matter of getting there in the first place?

in my case I tested it on the original ( poor ) wheels my bike came with to get an idea what to aim for. I tensioned my only pair of wheels I have built a bit more than those. They have been fine. touch wood
drossall
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Re: Spoke Tension Meters

Post by drossall »

Your tool looks like the Park one. If yours is Park, you can download the table or use the online app.
jb
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Re: Spoke Tension Meters

Post by jb »

A tension meter is mainly for getting them all the same tension, if you want to know where it should be approximately try out on a known good wheel of similar type.
Last edited by jb on 20 Jun 2020, 2:46pm, edited 1 time in total.
Cheers
J Bro
Brucey
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Re: Spoke Tension Meters

Post by Brucey »

'looking about the same' as another tension meter is practically meaningless when it comes to calibration; this way lies utter madness. Tiny manufacturing differences (which are often too small to measure (*)) will alter the 'slope' of the tool and this will screw the readings; at best they are possibly going to be meaningful at one reading only, hence my earlier suggestion about exactly how to verify the calibration for your use.

(*) depending on the design of the spring in the tool, a spring that 'looks the same' might vary in stiffness with the fourth power of the spring wire diameter. So for example the difference in spring rate between two springs with the same number of turns, one made with 2.00mm wire and one with 2.05mm wire, could be over 10%.

Remember that the calibration is only adjustable on these tools in terms of offset; if the spring in the tool is genuinely not absolutely identical stiffness then the calibration charts will be meaningless even if the rest of the tool is identical in every way, and even if some attempt has been made to set the meter calibration.

cheers
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Sweep
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Re: Spoke Tension Meters

Post by Sweep »

mercalia wrote:if not too late I would send the "meter" back as without a table it is useless?



Agree totally.

Send it back OP.

Where did you get it from?

This is cheaper than the Park and seems to get passable reviews.

https://www.chainreactioncycles.com/s?q ... at=product
Last edited by Sweep on 20 Jun 2020, 5:40pm, edited 1 time in total.
Sweep
Samuel D
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Re: Spoke Tension Meters

Post by Samuel D »

jb wrote:A tension meter is mainly for getting them all the same tension

Why do you say that? I haven’t found even the best of them to be much use for that; not when listening to the tone of plucked spokes shows smaller differences with greater reliability and more convenience to boot.

But to get the tension up against the rim limit is hard to achieve without a tensiometer. And the lighter the wheel, the narrower is the window between too low and too high spoke tension. For finding that absolute tension I find a tensiometer valuable.
NickJP
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Re: Spoke Tension Meters

Post by NickJP »

I recently sent my old Wheelsmith unit back to Wheel Fanatyk for recalibration: https://www.wheelfanatyk.com/store/ws-tensiometer-recalibration/.

But absent that service, it's easy enough to make up a jig for calibrating tensiometers:

Image
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NUKe
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Re: Spoke Tension Meters

Post by NUKe »

I once tensioned a wheel using a gauge to set them all to the same tension, ended up with a Pringle. Use the gauge only to check they are within range these days.
NUKe
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Brucey
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Re: Spoke Tension Meters

Post by Brucey »

Samuel D wrote:...But to get the tension up against the rim limit is hard to achieve without a tensiometer....


well, that would be more of a problem if that were a 'hard' limit. However it is not. Rims don't immediately fail if you exceed the tension limit slightly. Nor are they guaranteed to survive if you slavishly adhere to a tension at or slightly below that limit. In the real world rims crack because they are liberally sprayed with salty water (instead of something which will inhibit corrosion) and excess tension can help it along for sure but plenty of rims fail at tensions below the 'limit' too.

This may be a controversial view but I think that lower tension is always better for rim life (avoiding rim cracking at the drillings), right up until the tension is too low. 'Too low' is when the rim flexes excessively, or the spokes transiently go completely slack (or slack enough that the nipples back out, or the spoke moves around in the hub/crossing too much) in service.

So arguably you should be more worried about the lowest tension that is acceptable, not the highest. This tension depends on the rider and service conditions as much as anything else.

However for a heavily dished rear wheel, built light, and a strong rider, there is often no 'good' tension to set the wheel at. The NDS spoke tension is about half that of the DS and the NDS tension may always be 'too low' (as per above) whenever the DS tension is within the manufacturer's limit.

cheers
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Sweep
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Re: Spoke Tension Meters

Post by Sweep »

NUKe wrote:I once tensioned a wheel using a gauge to set them all to the same tension, ended up with a Pringle. Use the gauge only to check they are within range these days.

What percentage range do you aim for?
Sweep
iandusud
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Re: Spoke Tension Meters

Post by iandusud »

I'm not wishing to be controversial here but as someone who at one time built wheels every day and have built thousands of wheels which I consider were very good for their purpose, I would just like to say that I have never used a spoke tension meter. This is not to say that correct tension is not important. On the contrary in my experience the biggest cause of spoke breakage is under tensioned spokes. When prepping new bikes I would systematically tension the spokes of factory fresh bikes otherwise I knew I would have them coming back in no time with broken spokes. IME the key factors in building good wheels is selecting the parts that are suitable for the intended use and then building them up with even tension and enough of it. I appreciate that my ability to assess a correct tension without use of a tension meter is based on a lot of experience but I had to start somewhere, and I would suggest that as long as you have a reasonable amount of mechanical sympathy (without which you shouldn't be building wheels) then you should be able to estimate what is a reasonable amount of spoke tension. I would suggest do them up to what you consider to be reasonably tight and ride the wheel and recheck the spokes after a hundred miles or so. If they seem a bit loose then tighten them up and next time give them a bit more tension. There is certainly a place for accurate measurement but feel and mechanical sympathy should also be developed. It's a bit like a musician (of which I am one) who relies on electronic tuners and click tracks - you need to develop your ear and feel.
Pebble
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Re: Spoke Tension Meters

Post by Pebble »

Sweep wrote:
mercalia wrote:if not too late I would send the "meter" back as without a table it is useless?



Agree totally.

Send it back OP.

Where did you get it from?

This is cheaper than the Park and seems to get passable reviews.

https://www.chainreactioncycles.com/s?q ... at=product

Just a few comments on the purchase - It was off ebay (like this link see similarities with meter shown in OP which displays the comparison table) I suspect they're all off the same jelly mould somewhere in deepest china.

I did complain that no 'comparison table' came with meter and asked them to photo copy one and email it - however, since they can barely understand English they seem to think I am wanting a table (as in workbench) . However they have very kindly offered me a 50% refund which I accepted, the meter seems very good value for a tenner, and I will no doubt get plenty entertainment trying to calibrate it myself. I guess I could have easily went for the return and full refund (ebay are very good at that) but I think it is probably worth a tenner not to have to risk covid queuing at the post office.
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