Spoke tension isn’t something I’ve spent much time worrying about. Mostly, I ride on wheels that I have built, and mostly those wheels have stayed true and problem free. I haven’t ever had a broken spoke on any wheels I’ve ridden. The vintage wheels I use are usually well built but sometimes need some truing and dishing. So, I’ve never had to re-tension a wheel…until now.
The wheel in question is the Swytch e-bike front motor wheel which I installed about 7 months ago on my Bridgestone (see previous post). A few months ago I began hearing some strange noises from the wheel when braking hard or when going over a bump. It was a noise I recognized as a spoke noise. Spoke noises should not be ignored, as they could indicate a wheel on the verge of failure.
On the roadside after a particularly concerning noise, I flipped the bike over and spun the wheel to see if it was true – it was. Then I began looking at the spokes and found one spoke VERY loose – almost just hanging there. So, I did a quick tightening job with the adjustable wrench I carry and got it up to the same tension as the other spokes, and then rode home. Unfortunately, that fix did not cure the spoke noises. So, once home I again examined the wheel by plucking the spokes and became concerned when noting that the right side spokes were way less tense than the left. It look me a moment to realize that this front wheel is dished. The above photo shows that the flanges of the hub are not centered, to allow for the wheel magnets on the left side motor to have room to spin.
I didn’t have my wheel building tools at home, only a very basic spoke wrench of the wrong size (the spokes are 2.3 mm diameter – meaning a 13 gauge nipple). After squeezing pairs of spokes on each side of the wheel and observing a great deal of movement in the spokes, I realized I needed to up the tension to a minimally acceptable level in order to safely ride the bike over to my shop. Using my adjustable wrench I turned each spoke a quarter turn. I played a “G” note on my phone to aim for a reasonably correct initial tension, based on past wheels I have built. To achieve this I needed another quarter turn on all the spoke nipples. The wheel stayed fairly true, even after another round of “stress relieving”.
(C) Avocet, Jobst Brandt, the Bicycle Wheel, p. 57
What is stress relieving? According to bicycle engineer Jobst Brandt (RIP) in his famed classic, the Bicycle Wheel, “stress relieving is one of the most important operations in wheel building”. He goes on to argue that failure to relieve spoke stress is the most common cause of spoke failure.
To perform this procedure, you place your hands opposite each other on the wheel and grab pairs of parallel spokes, and then squeeze hard, continuing around the wheel until all the spokes have been stretched. If the wheel goes out of true in “two smooth waves” after this it means that spoke tension was too high. Brandt recommends getting spoke tension as high as possible, just short of causing rim failure. This will create the strongest wheel.
While I have always performed the stress relieving procedure on the wheels I have built, I haven’t considered that I should up the spoke tension to the absolute maximum. Instead, I have aimed for a musical note – somewhere between F and G – and also use a Park tension meter and chart to check my work.
When you buy a Park Tension Meter, you are also supplied with their handy tension guide which is organized by type of spoke (round, butted, bladed, etc.) and spoke diameter. So, once I was in the shop I located a correct spoke wrench, then determined what meter reading I was aiming for – the middle range for a 2.3mm spoke – which is a reading of about 27 or 28 on the Park Tension Meter. My initial reading was about 21, which did not even register on Park’s chart, being below the minimum recommended kgf of 54. This was after tightening the spokes 1/2 turn while at home! After continuing 1/4 turns around the rim, I was able to bring the tension up to the mid range of the recommended kgf of about 92, equating to a reading of 27 on the tension meter. After this, I performed the stress relieving operation, then did some minor truing. I checked the dish which remained correct, and then began riding the wheel again.
The wheel seemed fine for awhile but now I am hearing spoke noises again, meaning that the wheel is continuing to de-tension itself. I am going to guess that possible causes include bad spoke threads and low quality nipples. I’ve notified Swytch and they are sending me a new wheel. But will this solve the problem?
Jobst Brandt had a number of strong opinions about machine built wheels, arguing that the wheel building process for machine built wheels is essentially incomplete. An archive of his on-line writings can be found here. I’m going to research this issue further and may end up rebuilding the old wheel with my own choice of spokes and nipples. At a minimum I will perform the stress relieving and re-tensioning procedure on the new wheel to insure that I start out at the correct tension. And, I may consider upping the tension to the higher range on Park’s tension chart, just to be on the safe side.
“I played a “G” note on my phone to aim for a reasonably correct initial tension” – Thanks for this new emergency maneuver to file away in my memory bank, Nola!
😎
A few things I have long done when building wheels include not only squeezing spoke pairs, but first taking a punch and gently tapping the head of each spoke to set it into the flange, tapping each spoke above the J-bend to take out any bow, and using a screwdriver handle to shove the V-notch between crossed pairs of spokes toward the flange. As a final step, I put the wheel sideways on the floor and carefully push down on the rim in at least four places to de-tension the spokes on the side facing up, then flip it over and repeat. This is the trickiest step, as pressing down too hard can destroy the wheel. I then check it for final true.
Since this is a blog about restoring vintage bikes, it’s worth noting that vintage rims were nowhere near as strong as modern ones. If you try to get recommended spoke tension on a Fiamme yellow label, you are almost certainly going to destroy it. Oh, and I’ve broken plenty of spokes in my day, but that’s been largely due to being a cheapskate and re-using old spokes when replacing rims on my own wheels–something you should never do on a customer’s wheel.
Thanks for your comments. I think what Brandt is suggesting is to overtension the rim to failure through the stress relieving technique, then backing it down from there, to arrive at ideal tension for a given rim. Older rims don’t have recommended spoke tension specs available so you certainly wouldn’t want to tension it as if it were a newer rim. For vintage rims, I start with the musical note method (aiming for somewhere between F and G) and then double check a few with a tension meter to make sure tension is in the right ball park. It’s hard to remove the J-bend just using your hands – your method sounds interesting.
I have not had a properly built wheel de-tension itself without an identifiable reason. Oil on the nipple threads may prevent spoke prep compounds or thread lockers from functioning as they should. Or if no spoke prep was used at all that could do it. Additionally, a wheel built of low quality components will be less likely to stay true. Using good quality spokes is the best starting point along with clean threads and some spoke prep!
As for spoke tension, I do have a Park tensiometer but rarely use it. I can “feel” the correct tension when building wheel. Pre-stressing spoke pairs is an essential step for a durable built wheel.
I have had noise coming from a recently tuned wheel before but usually after a few rides it goes away. I check wheels frequently on the bikes I am riding. Most stay very true but I live in a town that believes roads are intended to loosen teeth! I know where most of the catastrophic pot holes are but still very rough asphalt . I have never broken a spoke either except when I got a chain “suck” once from a failed rear derailleur. Joe
Hi Nola, I couldn’t figure out how to get in contact. I was wondering if you take on restoration jobs? I have an 82-84 bianchi nuovo racing that’s pretty beat up and am looking to have it fully restored by someone who knows what they are doing lol. thank you!
Hi Chandler. I’m not taking on any new projects right now. Wish I could help. Hope you find someone to bring it back to life.
I just re-read this post; some useful information — especially the reminder to “stress-relieve”. I hope to build my second wheel (first built 20 years ago) and have been reading up on technique. The wheel will be a 700C rear fixed/ss wheel for a utility beater, like the first, one tho’ this one with 32 instead of 36 spokes.
I used Sheldon’s instructions on the first build which took well under 2 hours and turned out well enough to last without any need for re-truing for thousands of miles on a beater commuter fixed gear often carrying heavy rear loads.
If you have other suggestions for the neophyte wheel builder, I’ll be grateful to hear them.
Thanks.
Old thread now but I’ll throw in my 2cents. Spoke nipples work like any other fastener. If they are tight enough they stay tight. If the Park tension meter says they are tight enough and they keep loosening the problem could be the threads are just not much good. Then if they have been through a couple cycles of loosening even a thread that started good may be done.
My wheels are built with a touch of oil, whatever oil is handy goes on the threads. For very high tension wheels the lube is necessary, can’t complete build without. For ordinary tension wheels never a problem, does make the build easier.
In olden days most did build just too loose. Good builders did build tighter. One of my prized antiquities is a front wheel built by Oscar Wastyn in 1959. Fiamme Red rim to early FB quick release hub with 32 spokes.. Some extrapolation is necessary because Park doesn’t know about spokes as thin as these. At least 100kgpf. That wheel was likely little used when new, I’ve done a few thousand on it. Perfect true and no problems. When that wheel was acquired I was at my peak weight of almost 200#, which would have been just rare in 1959. Wheel didn’t care.
Stories about weak light rims are from 70s and 80s. Basically they rushed the extruding and the rims have wild variations in wall thickness. Happened especially on rims shipped to America. The variations make stress risers. Older rims were done slower, the guys making them knew the coureurs and boys racers using them. Demand from America was more than they could handle.
Try lightly bending the J-bend over the flange after inserting spoke in hub. Just a couple degrees. You’ll see the spoke now runs much straighter to the rim. Eliminates the new wheel pinging sound and need to touchup tension.
Check that the distance from spoke head to J-bend is appropriate. They are not all the same. Old thin steel flanges you need a washer to match newer spokes to the old flange. Extra heavy hubs for e-bikes, cycle trucks, I’ve seen cheaper wheels that seriously require a special spoke for the thick flange and they use normal stock.