unior tensiometer review

bj

Retro Guru
Just bought a 'unior' branded spoke tensiometer. Thought it would be a useful exercise in reviewing it for those interested.

After a rear wheel fight with a branch a couple of weeks back, putting in a serious wheel wobble, I started to read up about wheel truing. Initially trued it reasonably well using the bike frame as a truing guide. Having read about using the 'pinging' of spokes to check for tension balance it was fairly clear the balance was all over the place. Tried using a guitar tuner app to record the frequency, but it was too impractical to use. So I bought Roger Musson's wheelbuilding book and, as instructed in the book, have just finished building a truing stand, dishing tool and nipple driver (all out of bits and pieces in the garage - so no direct cost).

I decided to use the money saved to buy a tensiometer - but which one! They range in cost from £17 to many hundreds. Entry level middle ground appears to be dominated by the Park Tool version (about £70). However, there was an offer on the 'unior' branded version (£67). It had good reviews, came in a box, and included a calibration bar, so i splashed out and bought that one.



Cannot compare it directly with the other brands, having never used them, but 'out of the box' I would say the unior one is well made in general.
The deflection scale runs from 0 to 96, with the dial pointer not fully zeroed out of the box (reading -1). It is adjustable though.
The calibration bar is flagged as 62 units and when placed in the meter, it does indeed settle at 62. Spring tension can be adjusted if need be. There is a spoke gauge, which appears accurate for my butted spokes (2/1.8/2).
There is a deflection scale to 'kilogram force' units table for various spoke types.

Have plotted the scale conversion table for a 2/1.8/2 butted spoke. Does not appear to have a smooth relationship. However, discussion the internet indicates that the conversion from dial scale to tension, for any of the available tensiometers, is unlikely to be accurate and is only a guide. When using tensiometers, it is the 'relative' difference in tension that is the more practical indicator. When plotting data it is probably worth converting to 'apparent' tension, because of the non linear conversion. Will give example later - just off to make some rice pudding!
 

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Re:

Rice pudding now in the oven, so will give an example of how i used the tensiometer for the first time.

Wheels: Hope pro2 hubs, 32 spokes, 3 cross lacing, mavic x317 disc rim, unknown stainless double butted 2/1.8/2 spokes, 26".

Initially found it fiddly to locate the meter on every other spoke, because the meter's spring tension adjuster easily fouls the spoke crossover. Had to insert tool near the rim and then slide it back to locate the meter on the thinner part of the spoke. The scale reading would vary by 1 or 2 units depending on where along the spoke i used it. To be consistent i placed a bit of red tape (seen on the initial photo) to use as a distance marker from the rim. This placed the meter just off one end of the 2mm butted end nearest the rim. The reading would vary by +/- 1 on repeated measurements, so i used the best of three. If i do not completely release the lever on taking a reading, there is stiction or similar that causes the reading to over read by 1 unit. After a bit of experience i found that i became more adept at locating the meter and releasing it fully, and the repeatability of the readings generally settled down to remain at +/-1 one. Without doubt, I found that numbering the spokes with a pencil on the rim was very useful on keeping tabs on where you had got to.

After a couple of hours of messing about with both wheels, I felt i had enough of a repeatable method to take a set of readings.

So here is the data for the before adjustment, plotted on a radar plot. The wheels run true and round, but as can be seen, the tension is somewhat erratic. I have highlighted the spokes that lie outside 20% of the average. A highest reading of 155kgf was certainly tight when adjusted, so i feel there is some usable correlation with actual tensions. The plot certainly helps visualise the tension spread.




So using the plot and meter i set about adjusting the out of spec tensions, and replotted the data. In my enthusiasm of the new toy, i then went on to using subsequent plots to readjust to tighter tolerances. Here is the data for my final adjustments:



Very pleased with the result, and would say on balance i do not regret having bought the tensiometer. Whether it is any better than having bought a cheap £17 one I will never know. I rather suspect the cheaper one will have been quite effective, because you are only after relative tension in general. Next step is to build up a wheel from scratch.
 

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Thanks bj for taking the trouble to share your experience with us. I've rebuilt a front wheel but will have a rear one to do after flat spotting the rim. I bought a cheap tension meter when I did the front wheel but it's still in the box. You've inspired me to get it out when I do the rear wheel. I've built myself a dishing tool and aim to build a truing stand. Thanks Bill
 
Very easy in Excel spreadsheet to create the radar plot.
Enter the values in a column/columns
Highlight the column/columns.
Select 'Insert' tab
Select 'Other Charts' within 'Charts'
Select radar plot

Might have to change scale etc to suit.
 
Re:

These posts, added to the fact I have lots of wheels to true and tension, inspired me to buy a cheap "deckas" tensiometer:

https://www.ebay.co.uk/itm/363011924315

It arrived today. It is very well made and seems to work well. Unfortunately it doesn't come with a conversion table for deflection readings. The scale (and overall design) seems much the same as the Park TM-1 so I plan to use the table at the link below and aim for roughly 125kg... but more importantly for even tension. A quick measure of my known good wheels gives tension readings roughly where you would expect...

https://www.parktool.com/blog/repair-he ... easurement

For now I'm going to assume that the spoke diameters in the Park scales would be for the middle part of the spoke with butted spokes...

:?

It's going to be interesting to compare wheels I've built myself (without a tensiometer) to new machine built wheels and old wheels which have stood up well...
 
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