Prior to the testing, I did some online searching for any answers and looks like black vs silver spoke choice has been a continued debate across multiple online forums for a while now.
The majority suggests that there should be no noticeable difference, mostly merely aesthetic, and that the colouring of the spoke shouldn't give or take any other characteristics to the spoke. According to Easton, when confronted with the question "What's the difference between black spokes and silver spokes." the answer was as follows: "Nothing, except for colour. Black spokes are made by applying a black oxide coating (not anodizing) to the spoke. It's a topical coating for cosmetic purpose only, and does nothing for the function or strength of the spoke."
But here I wasn’t in the search for noticing the difference in fundamental spoke characteristics like strength or longevity of the spoke, but rather observing its behaviour when mounted in the tension meter. And how can it consequently affect or mess with the spoke tension meter readings. Should it be wise to use the same spoke tension charts for black and silver spokes without any real concern?
And something even more intriguing. Testing spoke colour variations of the same shape and thickness would also lead me to yet another answer. What is the difference in spoke tension meter readings across different spoke brands. As mentioned in the article Spoke tension – The definitive guide to spoke tensioning, according to DT Swiss technical support, spokes from different manufacturers behave differently and so it is inadvisable to use spoke tension charts across different spoke makers carelessly.
Spoke tension meter
Naturally, if we want to notice even the slightest difference in spoke tension meter behaviour across black and silver spokes, we first need a precise, highly accurate tool. Meaning all low-end market tension meters fall out of the option as they wouldn't be susceptible to expected small deviations in tension readings.
Having said that, for testing purposes, I opted my Birzman BM15 spoke tension meter with a Mitutoyo® dial indicator of high accuracy that scales to 0.01mm. Such a precise scale would then alert me to the smallest of change in tension meter readings deviation across black/silver spokes of the same model.
For the purpose of tension testing, I got all available spoke models from DT Swiss and Sapim in classic, J-bend shape and in silver and black colour.
Tested spokes included all three types - straight gauge, single butted and also double butted – and also two main shapes, round and bladed as well. Also, all spokes were almost identical in length, between 265 and 268mm to fit my tension meter calibration device.
Repetitive readings - the testing method
Making reasonable conclusions or drawing general consumptions based on just one spoke colour sample would be unwise, but it would still give us the ballpark for additional thinking regarding the matter.
Moreover, to ensure testing results would be as valid as they can be I had to standardize the process of taking repetitive readings as controlled as I could. These factors included:
- All spoke models were basically the identical length. The length of the spoke butt wouldn’t really play a role in results deviation.
- The centre of the mounted spoke in the tension meter calibration device was marked for the tension meter to be placed exactly in the same spot every time when taking a tension reading.
- Careful, controlled spring release for tension readings not to be deformed.
- Weight of the tension meter. Using the tension meter calibration device, the angle and position of the tension meter would be the same every time. Not to let the variable weight of the tension meter when held in hand affect tension meter readings, leaving it leaning (hands-free) on the spoke would guarantee comparable readings.
- Results would have to be taken multiple times, averaging spoke tension meter readings and confirming the deviation isn’t problematic.
Results - tension meter readings
Taking only one reference tension reading for each spoke would suggest there may or may not be difference between the two spoke colour variations but at the same time it would not provide enough data to compare the absolute difference in tension itself. Therefore, for every spoke model and colour, three reference readings were taken – for 90, 100 and 110kgF of applied tension on a spoke in total.
Note: for the purpose of this article, we are not comparing tension meter results to a reference spoke tension chart of any kind, but rather we are observing deviations among spoke colour variations and across competitor brands tested.
Results that show tension meter readings are grouped according to competitor spokes that are same shape and dimension.
Straight gauge spoke, round 2.0mm
The first case was represented by the workhorses of the industry, single butted 2.0mm round spokes. Looking at Sapim Leader spoke, the tension meter readings difference between silver and black were somewhere from 0.03 and 0.05. In simple terms, if we made a simple tension chart according to silver spoke readings, and then use it on black version of the same spoke, we would be around 5kgF short in tension. On the other hand, having a tension chart made from black Sapim Leader spoke would have us think we have a 100kgF on the silver spoke at 2.56 but it really would be around 5kgF (≈5%) excess tension applied on the spoke.
Looking at DT Champion, readings are little short, but really not that far from Sapim Leader results, although DT Swiss technical support warns from careless use of tension charts across different spoke brands. What is more interesting is that for DT Swiss Champion spoke, the tension meter readings are much more uniform between black and silver spoke colour variation.
The next to be tested in the range of round shape were the spokes with probably the most versatile range in terms of lightness and strength. Sapim Race and its the direct competitor, DT Competition, both double butted, with 1.8mm diameter in the central section.
Black DT Competition spokes on average came a bit short in terms on tension meter readings, constantly showing from 1 up to 4kgF less than the silver ones.
Note: Looking at the shape of the spoke, one could quickly notice that DT Competition has a different length of spoke butting. Specifically, the upper, 2.0mm part, is significantly longer than at Sapim Race spoke.
However, looking at Sapim Race spokes, the tension meter readings were at first (at 90kgF) a bit short for the black spoke, compared to the silver version, while having applied the greater tension on the spoke the situation then turned around.
Double gauge spoke, 2.0/1.8/2.0 mm
Turning focus to the lightest round spokes on the market, double butted and with 1.5mm in diameter, both Sapim Laser as DT Revolution shown significant differences in tension meter readings between black and silver spokes.
Meaning, making a tension chart for one colour version of the spoke and then use it on the other colour finish of the same spoke model would show us up to around 8kgF of either excess or shortage in spoke tension. However, here, the differences between silver and black spokes for DT Revolution are a bit smaller (≈6kgF), while tension meter readings are on the contrary higher for black spoke compared to Sapim Laser.
Double gauge spoke, 2.0/1.5/2.0 mm
Lastly, how would silver/black bladed steel spokes behave when inserted into our tension meter?
If we first look at DT Aerolite, differences are almost negligible as tension meter readings for black and silver spokes are not far off. Therefore, one could easily use the same spoke tension chart on black as well as silver spoke version. And the same goes for Sapim CX-Ray spokes, except here tension meter readings are not that uniform as the differences are a bit more noticeable and go up to 5kgF of tension.
But stop for a while and take into consideration the difference in spoke tension readings between the two spoke manufacturers. On the market DT Aerolite and Sapim CX-Ray are known as notorious fierce rivals as their dimensions match perfectly. But notice how spoke tension charts vary between these two spoke makers. Judging solely by dimension, using a spoke chart of Sapim CX-Ray on DT Aerolite would made us apply an excess of almost 10kgF of tension and vice versa.
Bladed steel spoke, 2.0/0.9-2.3/2.0 mm
With every little experiment, other interesting findings may also arise. Did you sometimes wonder how great is additional stress you put on the spoke while taking spoke tension readings with your tension meter?
Having already 100kgF tension on the spoke when I mounted my tension meter, the scale shown total of 102.8kgF or just around 3kg of change in spoke tension.
Looking at spoke tension readings of such a wide range of all these spokes while having in mind the underlying question of this article, we can confirm there certainly are differences in spoke tension readings across black / silver versions of the same spoke model. Results indicate that spoke colour variations behave differently in the spoke tension meter. However, any further conclusion would be invalid as there isn’t any real pattern in these deviations.
On the other hand, although indirectly, this article also generated some useful findings regarding differences between spoke tension readings for the spokes of the same shape/dimensions of competitor spoke manufacturers. Results show that spoke tension charts of nearly identical spokes (shape/dimension) differ between spoke makers. While perhaps the least noticeable differences appeared at the workhorses of the industry, 2.0mm straight gauge spokes, the case of bladed 2.0/0.9-2.3/2.0mm spokes showed the complete opposite.
All in all, especially when operating with a precise spoke tension meter, it is highly advisable to make a range of specific, custom spoke tension charts.
Happy wheel building!