Fail.

I said:

"The bike is almost 40 years old and if these are the original wheels the spokes are probably at the end of their useful lifespan... 3 broken spokes is an indication that they are suffering from fatigue, either through improper tension or simply from old age."

But I will agree that a well built 40 year old wheel that has not been used will probably be just fine... but it would appear that this one has seen some miles and if it was poorly built from the start it may have not taken much to cause spoke failure.

There is nothing that suggests that this bicycle was new old stock and was more than likely ridden before.

Actually, fatigue would occur whether the wheel was tensioned correctly or incorrectly. Fatigue happens with every revolution of the wheel. Incorrectly tensioned spokes would only hasten the process because the the loading and unloading stress levels would be greater than a properly tensioned wheel.

Sixty Fiver my apologies, I didn't take care to re-read your post before I posted my response, and I obviously didn't register correctly the gist of what you wrote. However, the essence of what I getting at was the concept of "old age". I'll reiterate, finished metal products do not age with time, only with use or through chemical processes (e.g. corrosion or temperature).

iab, I'm not sure if you're familiar with the concept of "fatigue limit". It is complicated to describe so rather than attempt it here I suggest those unfamiliar look it up to their satisfaction.

In a nutshell, some materials, e.g. steel have a fatigue limit that allows them to be designed into an application such that they have infinite life, as long as the design is manufactured, assembled, and used according to the design specificiation.

By the same token, with an educated guess as to the realistic maximum number of cycles a component may be subjected to in its expected lifetime, a component can be engineered to have a fatigue limit that is close enough to infinite that nobody will know the difference, unless something goes wrong like the designer screwed up or it wasn't applied according to the design specification. I suspect garage door springs and bicycle spokes fall into this category.

The fact that I have had to replace all the springs on the 5 garage doors that I've owned at least once appears to say otherwise. Likewise the fact that the local hardware store has always had a good supply of replacement springs on display in a fairly prominent location.

OTOH, my luck with bicycle spokes has been better (with the exception of one tandem wheel that I finally gave up on and replaced). The spokes have generally lasted as long as the rim and in some cases have made it through one or two rim replacements. So they've at least held up for one or two hundred thousand miles.

I am familar with fatigue limit. What I don't know if spoke manufacturers have engineered that into their product. If I were to guess, no spoke has been designed to have an "infinate" life. Too heavy. Too poor of a business model.


BTW, what would you consider infinate? I'd say at least 100K miles.

No worries... I am well aware that unless materials are subjected to stress that they will not fatigue and "old age" referred to bicycles that have been kept in somewhat regular use and find that most are not maintained at an acceptable level.

I re-laced the wheels on my 1957 Peugeot as despite having nearly no miles and perfectly true rims the spokes developed some significant corrosion from being stored for most of the bicycle's life.

I build wheels for a living... understand quite well how improper tension will greatly shorten a wheel's service life and deal with a lot of wheels that have relatively few miles that have serious issues due to poor builds.

I do not know what the fatigue limit is for spokes as this is determined by the quality of the build and the type of use they are subjected to and when you are dealing with a wheel you have no history of it is always prudent to replace the existing spokes.

This is why most shops will not re-use spokes as they cannot guarantee the work... my experience is that a properly built wheel will stay true and need very little attention and that the rim will wear out before the spokes do.

A few of my bikes have had their rims replaced several times and I have re-used the existing spokes knowing who built the wheel (me) and what the useage was like... some of these spokes have seen 30,000 miles and the rebuilt wheels stay as true as the originals.

Modern spokes are so much better that what was available 40 years ago... was not building wheels then but have serviced a lot of bicycles that are much older than this.

I am strickly a novice at wheel building. Did it 30 years ago on a regular basis and thought it worked well. At least for the time.

Last year I broke two spokes on my 'Nago, DS rear. I decided something was wrong so disassembled it. I found that many of the spokes were different lengths, not bu much but enough to be concerned about using nipple engagement reletive to end of spoke a problem. I also found two different spoke sizes in terms of gauge configuration. One was a straight gauge with the other DB. I seperated them by length, got rid of the odd balls and purcahsed replacements for the disgarded ones. Then laced up.

I also bought the TM-1. Part of the inconsistant readings, aside from where on the spoke you test, was a loose fastner on the tool. I used a spreadsheet to capture the tension readings along with a spider graph to be able to see the spoke tension distribution. My hope was that I could learnt to compensate. What really nailed it for me was downloading the Excel tool from Park Tools in the TM-1 site. Getting within 20% was a huge plus. Refining was made eaisier once I was within range. The other thing I learned was that you can't hurry this with taking big steps. I backed off and was able to align and get consistant tension by starting at readings of 2 on the TM. Once everthing was true at that level, taking to the right level was much easier with smaller adjustments.

little update - went out and picked up a spare wheel for the super course and all is well there - that much said - i have also decided to rebuild the wheel set - i am gonna pick up a true stand first though - the tension meter is on the way and already have a WAG

as far as spoke length - 295mm looks good with the existing spoke pattern of the wheels (i am assuming that the rims are ok - did not dissassemble from the hub yet though)

quick noob question - spoke length should be the same on both sides of the rear right - the drive side will be typically of higher tension so as to dish the wheel in the frame - but i should be using the same length correct?

i ask because the lengths of the actual spokes that came on this wheel vary quite a bit - just by eye i can tell with all the spokes coming from through the nipples (suprised i didnt rim flat on some rides - though the tape was thick enough i suppose to protect the tube)

Drive spokes are often slightly shorter to account for the offset and dish although same length spokes can be used with some builds... would be best to disassemble the wheel slowly and carefully (do not cut out the spokes) and input the hub and rim dimensions into a spoke calculator to make sure they are exact.

Unlike horseshoes and hand grenades, spoke measurements cannot be close enough if you want a solid build.

With a 120mm hub the offset and dish will be minimal so same length spokes will work fine... newer wheels with wider cassettes have more offset with typical hub spacing and this is where drive side and non drive lengths will have the most variance.

Tandem hubs and speciality hubs are wider and allow for wide range gearing (ie 9 speed) and little to no dish.

sixty fiver - thank you for the advice - i have enjoyed this thread very much and feel like i learn so much here from everyone