Need some help on spokes

[buckstopper]

I attended a talk given by Brad Hunter of Velomax/Easton at Cyclelab a year ago. He spoke, yes spoke, about using sound by plucking the spoke with a hard plastic object to gauge equality and I assume amount of tension. He didn't pooh pooh the tensiometer but said he preferred just listening to the sound. Marketing hype or science? They are lovely hoops, though.

[Johan Bornman]

I attended a talk given by Brad Hunter of Velomax/Easton at Cyclelab a year ago. He spoke' date=' yes spoke, about using sound by plucking the spoke with a hard plastic object to gauge equality and I assume amount of tension. He didn't pooh pooh the tensiometer but said he preferred just listening to the sound. Marketing hype or science? They are lovely hoops, though.[/quote']

 

I have to agree with your spoke plucker. You don't even need a pick, just pluck it with a fingernail and go right round, plucking each spoke in turn. You'll quickly identify any errant spokes as well as find an audible guide to where the join in the rim is.

 

The interesting thing about a perfectly-trued wheel is that not all its spokes are in the same tension. This is because the rim is seldom uniform. The joint is particularly hard (ort soft, depending on how it was quenched after welding) and often rims are not round to start off with. Therefore, should you carefully equalise all spokes with a tensiometer, you'll have a wobbly wheel.

 

MY experience with Easton wheels are good. Some of the other, more famous boutique wheels don't fare so well, as is evident from the OP here and other reports on The Hub.

 

 

 

 

[buckstopper]

During the talk he asked someone to fetch him a random Easton wheel. The guy brought him a Circuit off one of the Cervelos standing on the floor. He plucked and the tone was very uniform. He then asked for a wheel of another brand. He was brought a Hed........ Needless to say it was out of tune, so to speek, ja speek. 

[Delgado]

thanks for all the input guys....been really helpful.  I have also ordered the following for me.......easton circuit wheelset

[Dr. Watt]

Johan Bornman

 

While reading this thread I was really interested to learn your opinions on spoke tension meters. Forgive me if I've missed your answer to this somewhere in the thread, but do you never use a spoke tension meter when building wheels? Or do you only use it sometimes? If so, how do you decide when to use it and when not to use it?

 

Looking forward to reading your response.

 

[Johan Bornman]

Johan Bornman

 

While reading this thread I was really interested to learn your opinions on spoke tension meters. Forgive me if I've missed your answer to this somewhere in the thread' date=' but do you never use a spoke tension meter when building wheels? Or do you only use it sometimes? If so, how do you decide when to use it and when not to use it?

 

Looking forward to reading your response.

 

[/quote']

 

My spoke tensionmeter is somewhere in storage, since I'm in-between houses. It'll come out in January and then gather dust in my workshop. I therefore never use it, but I used to haul it out occasionally to convince myself that it is a really useful tool because I spent a lot of money on it. I brought a very nice Wheelsmith one in from the US once. Now I don't fool myself anymore.

 

But lets start at the beginning and then my position will become clear.

 

Spokes in a wheel support a load on the hub by the reduction in tension of the bottom few spokes, called the load affected zone. The size of the zone (and therefore the number of spokes inside it) is determined by a) the number of spokes in the wheel and b) the thickness of the rim.

 

The sturdier the rim, like aero rims, the larger the zone and therefore more spokes are inside the zone, with each spoke supporting less of the load. With strong beefy rims you need less spokes but have to accept that each spoke will do more of the work.

 

The more spokes in the wheel, the closer together they are and therefore more of them fall in the zone by default.

 

Thus, in supporting the load, a wheel's spokes never increase in tension, but the bottom few spokes just lose tension one by one as the wheel rotates. They regain tension as they rotate through the load affected zone. Pedalling action only increases tension by about 5% on a 32-spoke wheel and is therefore negligible when one is concerned with overtensioning a spoke. Likewise, when braking with a disc-braked bike, tension on every second spoke is increased by a small percentage, again not important when exceeding maximum tension is concerned.

 

It is important to understand this, it is the premise to wheelbuilding: a spoke never gains tension in use, only temporary reduces its tension. (But never to the point where it is not in tension anymore).

 

Therefore, the strongest wheel is one where you have maximum tension in the spokes. That way, you know you have lots of tension in the bank and you can take a way lots before the spoke goes slack and the wheel collapses.

 

A wheelbuilder's challenge is to find "The maximum tension THAT wheel can support. It is different for every wheel (but reasonably consistent for wheels made up from the same hub, spokes and lacing pattern, as in a factory) because it is affected by the choice of hub, spokes, rim and cross pattern. This figure is not published by anyone because there are infinite number of combinations. The wheelbuilder has to arrive at this point by experimentation. We have some tools at our disposal: a wheel collapses when you exceed maximum tension or, nipples cannot be turned anymore. Once you've reached this point, you know you have the tightest spokes that particular wheel can handle. If the rim is a lightweight box section rim, it'll collapse. If the rim is a beefy V-section, it'll not collapse, but the nipples will gall or the spokes with wind up so badly that you cannot tighted them anymore

 

Collapse is easy to recover from, you simply back of three or so turns on each nipple and then true without further tensioning. However, once you've built a few wheels you no longer have to approach the point of collapse, other subtle signs tell you you are approaching the maximum tension.

 

Once you've reached a point where you are happy with the overall tension, then you true, stress relieve, de-twist the spokes, true the wheel radially (take out any hops), stress relieve and finish off the wheel.

 

Should you be building many of the same wheel, then you may want to use your tensiometer so that you can put a number to your experimentally-determined maximum tension. However, it is more than likely that your next wheel will be different and then you're back to square one. 

 

What about checking with a tensiometer if all the spokes are equally tight?

 

A wheel that is perfectly true never has absolutely even tension in its spokes (and I'm not talking about the disparity between left and right spokes on rear wheels). The rim is not uniform and therefore some spokes have to pull harder to make it true. Rims are aluminium extrusions made from semi-molten metal pushed through a die. This is an imperfect process and irregularities are common. Some places are thicker than others. Further, the joint greatly affects the rim's hardness. It could be either harder than the rest of the rim or softer, depending on how the welded spot was cooled. Spokes there are always noticeable "off" compared to the others. Rims are seldom round too, and can be as much as 5mm out of true when new. That's why you have to measure them in at least two places and average out the diameter before calculating spoke lengths. This greatly affects spoke tension uniformity.

 

However, a skilled builder understands this and has a mental picture of his wheel's spoke tension when the wheel is finished. This he gets from known irregularities in the rim (weld and ovalness) and will usually confirm this by plucking the spokes at the end of the build. Should one spoke be significantly out of tune with the rest, then he will investigate by "looking" at the spokes in the immediate vicinity of that suspect spoke and make a call based on that.

 

Back to tensiometers. They simply put a number to a state that doesn't need quantification, unless, like I said, you want to repeat a particular wheel many times over and put an absolutely consistent product out of your factory.  It's a little bit like micrometers on wheelstands. Why do you need to know the number of the error?

 

An audible indication of the evenness of your wheel's tension is quick and easy to comprehend, whereas a tensiometer is clumsy and confusing, not to mention, quite inaccurate. It works on measuring the deflection in a spoke between two points. Friction greatly affects it and most of these devices are crude - the Park Tool comes to mind. They will often indicate an even tension when an audible signal will confirm otherwise.

 

What about eyelets pulling out of rims from too much tension?

 

These are usually under-spec'd rims designed for the weight-weenie market and simply don't have enough meat in there to last long enough. They usually have only a single eyelet when an eyelet and socket is clearly the answer. V-shaped rims have an inherent strengh that can get away without sockets.

 

However, spokes pulling out of rims is not a problem caused by overtensioning, but by the rim fatiguing around the spoke and weakening. If the rim is as strong as it should be, the stretching is mostly taken up by the spoke and not the rim, and the rim will last until the braking surface is worn out.  Hard-anodised rims is another story altogether. Hard anodising weakens the rim considerably since it is a layer of ceramic that is half on top of the rim and half embedded in the material. With flex, little cracks develop which propagate into the softer aluminium and develop stress cracks very quickly. Think of bending a knee with a nice thick crusty scab on top.

 

Rim and hub manufacuters don't publish tension data, if they had, it would be different for each spoke combination. The fact that they do so for complete wheels is neither here nor there. We saw from data someone kindly posted here that the variation is so big, it is laughable.

 

Finally, one of my students recently bought a tensiometer and retensioned his wheel he build in class using his new toy. He ended up with a wobbly wheel. He was big enough to admit his folly (he was warned) and he came and showed it to me. It was quite funny, the spoke tension was absolutely even but the wheel wobbled by 5mm in some places.

 

It was a long post, but thanks to those who persevered. I hope I explained my case adequately, but please, shoot with more questions if something is unclear.

 

 

 

 

Johan Bornman2007-12-18 22:18:38

[Red Zone]

Well done Johan, 6:15 and on the hub with such a comprehensive answer, I am well impressed. Its great to understand wheel dynamics, helps look after your bikes and identify problems. Dont think I wil be trying wheel building anytime soon.

[Guest Big H]

Klink vir my nogal weird dat mnr Bornman , as hy so slim is soos sy stories, nie as 'n konsultant gehuur word deur Shimano, DT Swiss en talle ander maatskappye. Dink net hoe goed kan hy hulle wiele vir hulle regmaak dat selfs vetties soos ek die wiele kan gebruik. Is dit dalk net 'n geval van "in die land van die blindes is een-oog koning"??????

 

Steve if I were you I would fire Doug (even though he is one of the most respected wheelsmiths in the country) and employ this guy with the yellow saddle.

 

Is he just one of those products hiding away in South African obscurity waiting for a cycling world to discover. WOW !!!!!! ons sal dan kan se ons ken die Piet!!!!!!! Dalk vra Zuma hom om as raadgewer vir hom op te tree.

[Windbreaker]

 

Big H' date=' you introduced JB's name to the thread and you took two low blows without adding ANYTHING of value to the topic. It's not like you are debating a difference of opinions - you are just trashing him. Why?

 

[/quote']Make that 3 low blows without adding anything of value. JB thanks for the interesting stuff.

 

[Wannabe]

Big H' date=' you introduced JB's name to the thread and you took two low blows without adding ANYTHING of value to the topic. It's not like you are debating a difference of opinions - you are just trashing him. Why?
[/quote']Make that 3 low blows without adding anything of value. JB thanks for the interesting stuff.

 

Any unresolved issues here that we should know of, BigH?

[Guest Big H]

No unresolved issues but who will you trust, a witchdoctor or a heart specialist with PROPER training and most likely research behind his name when you go for open heart surgery? It is like cooking fondant....... you can use the droplet in the water technique and you might get proper fondant, but if you use a proper thermometer you WILL get proper results, even the most inexperienced of cooks.

 

Mr Bornman advocates the use of a "musical ear" to tune his wheels, almost like tuning a guitar. What will happen if you cannot hear his melodious "twang"?????

 

He is our self proclaimed Hub and expert on wheels. Has anybody ever queired his traing ???? The companies he critisizes are well established in the realm om wheel building designing and development. Who would you believe, the large companies with all their expertise, companies like Park, Pedro's, DT Swiss, Shimano etc etc etc or our resident self trained "expert", who runs a business and advertises on the Hub for his own gain?????

 

Glo maar wie julle wil. EK weet JB gaan nou weer my posting uitmekaarskeur of vir my 'n dreigende PM stuur. Wie gee om.... sien die worry in my oog. Ek ken 'n polisverkoopsman as ek een sien of iemand wat sy eie produk ten koste van ander wil bevoordeel.

[Jason]

He is our self proclaimed Hub and expert on wheels. Has anybody ever queired his traing ????

I had a problem with my Mavic Open Sport... Went to Dr. Bornman's house and the wheel is riding like a dream! No problems... Trust me, the man knows a lot about wheels and I would recommend Johan to anyone.

I was referred to Johan by a very well known and trusted source

Come come now my son... It's Christmas.

[IanJ]

JB, I don't understand one aspect of your detailed explanation above.

 

If the tension of the spokes on the lower portion of the wheel decrease as they rotate surely that would imply that the opposite spokes would increase in tension correspondingly?

 

 

[greatwhite]

 

What about eyelets pulling out of rims from too much tension?

 

These are usually under-spec'd rims designed for the weight-weenie market and simply don't have enough meat in there to last long enough. They usually have only a single eyelet when an eyelet and socket is clearly the answer. V-shaped rims have an inherent strengh that can get away without sockets.

 

However' date=' spokes pulling out of rims is not a problem caused by overtensioning, but by the rim fatiguing around the spoke and weakening. If the rim is as strong as it should be, the stretching is mostly taken up by the spoke and not the rim, and the rim will last until the braking surface is worn out.  Hard-anodised rims is another story altogether. Hard anodising weakens the rim considerably since it is a layer of ceramic that is half on top of the rim and half embedded in the material. With flex, little cracks develop which propagate into the softer aluminium and develop stress cracks very quickly. Think of bending a knee with a nice thick crusty scab on top.

 

Rim and hub manufacuters don't publish tension data, if they had, it would be different for each spoke combination. The fact that they do so for complete wheels is neither here nor there. We saw from data someone kindly posted here that the variation is so big, it is laughable.

 

[/quote']

 

Nicely explained. You mentioned students - what do you teach?

 

I posted the info on spoke tensions and I made the same observation at the time - the tension range is huge. On that score, have you considered that the tensions may have to do with rim fatigue as well as spoke life. i.e. too high a tension brings on rim failure sooner.

 

Moving on to your other statement: "V-shaped rims have an inherent strengh that can get away without sockets." The highest stressed point on the rim due to deflection in the load affected zone is the inner (point of the V) and outer (top of braking) surface. While such rims have greater vertical stiffness, I would suggest the peak stress at the inner and outer surface is much the same. Invariably such rims also have lower spoke counts and spoke tension is consequently higher, therefore the stress imposed on each eyelet is higher. I believe, manufacturers choice to leave out sockets on deep section rims has more to do with their inability to fit them into the narrow confines at the bottom of the V than inherent rim strength. My experience, while limited, bears out that these type of rims highly prone to fatigue failure around the eyelet.

 

 

[Johan Bornman]

JB' date=' I don't understand one aspect of your detailed explanation above.

 

If the tension of the spokes on the lower portion of the wheel decrease as they rotate surely that would imply that the opposite spokes would increase in tension correspondingly?

 

 

[/quote']

 

It is quite hard to visualise, but it doesn't happen the way you describe. Only the bottom spokes reduce in tension, the rest stay the same. It is exactly like a car tyre. Have a look at a parked car. The bottom of the tyre is squashed flat without the top part stretching downwards.

 

If you are familiar with Newton's laws and understand them, it'll help you to think of it as a force that attracts an equal and opposite force. The wheel presses on the road and the road presses back. The "press" is between the hub and the road and the area above the hub remains unaffected.

 

If that fails to switch on the right neurons, visualise the wheel horisontally. You are holding it by a long extended skewer with a handle on each side and pushing it against a wall.

 

 

[buckstopper]

Mr Bornman advocates the use of a "musical ear" to tune his wheels' date=' almost like tuning a guitar. What will happen if you cannot hear his melodious "twang"????? 

[/quote']

 

Big H, so does Brad Hunter, who put Velomax wheels on the map. He designs, has built and oversees production of some of the best factory built wheels available - and advocates twang rather than the tensiometer.

 

In the process of getting a 20 spoke powertap hub for my daughter, planning on mating it to an Easton rim tempest 2 clincher with cx rays. JB, would you do this for me?