|Custom Wheel Questions||steveF|
Oct 13, 2001 8:20 PM
|Would a wheel built with DT Revolution spokes be built at the same tension as with DT double-butted spokes? Are brass nipples significantly heavier than alloy nipples, and-if so-are they worth it for strength? Is there any trick to Revolution spokes such that I would have to be very selective about who trues the wheels once built? Bottom line is I want wheels as light as possible but want them strong and relatively trouble-free. Thanks!|
Oct 14, 2001 10:51 AM
|It's the rim, not the spokes themselves, which determines the maximum - ideal - tension. When the tension goes beyond this then the rim will collapse into a saddle shape with only a little persuasion: but the spokes, even thin ones, will by then be nowhere near failure.
The weight saving that aluminium alloy nipples grant over brass ones is slight, and they can be troublesome. The edges round off easily unless you always use a top-quality spoke key, and their thread friction is high relative to brass, making it more likely to accidentally leave residual twist in the spokes. They're ultimately perfectly useable if you really want to save that 30g or whatever, but I can never be bothered with the extra hassle.
Revolution spokes are in themselves far more prone to twisting during building than other DB spokes, as their cross-section is so small. The same applies as for the nipples, really: You can with great care make the wheel reliable, but it's a lot more hassle... and for little gain.
I'd stay with boring old DB spokes, brass nipples, and about 32 of each per wheel. Well-built, they'll be trouble free, and you'll only notice the weight difference if you have electronic scales.
Oct 14, 2001 6:26 PM
|Although some parts of the above statement are true many are not.
1.It IS the spoke that determines maximum tension, refer to the Wheelsmith tensiometer and this will give you the maximum tension for different gauges of spokes, because there is a different max tension with different gauges of spokes.
2. Alloy nipples are considerably lighter than brass, plus they are on the outside of the wheel allowing for quicker accelaration.
3. Yes, there is more friction in an alloy nipple but any experianced wheelbuilder knows to use an oil to prevent friction.
4. The so called "residual twist" is actually between the nipple and the rim, not the spoke inside the nipple.
5. If you have the wheels built and serviced by an experianced wheel builder you will not have to worry about the alloy nipples rounding off.
Hope this helps you in your desicion.
DT certified master wheelbuilder
|DT Revo's and other thin spokes do require more time||JS|
Oct 14, 2001 9:15 PM
|to build with especially when using aluminum nipples because the binding between the two metals leads to easier spoke windup regardless of using oil. Heck I don't even use spoke prep anymore, I just build with oil now on all my wheels. These wheels can be built very durable it just takes a little more time to get right.
Oct 15, 2001 3:15 AM
|1. If you use a tensionometer you will record different tensions; thinner spokes are more flexible. But if you determine correct tension the best way- by increasing it incrementally until the process of stress-relieving begins to distort the rim, then this will be happen at the same time, regardless of the spokes used: the rim determines the maximum tension. Not many people have tensionometers anyway, except of course Certified Master Wheelbuilders.
2. What is 'considerably'... anyway, I thought the acceleration myth (something cyclists don't ever really do) had been debunked long ago.
3. Oil is always used but it still makes alloy nipples trickier to use than brass, under the equivalent oily conditions. Brass is a natural bearing and beneficial here.
4. Come on. It's the spoke which harbours the twist: when it is unloaded, the spoke turns in the nipple... if the nipple turned in the rim, then the effective length would't be unchanged and the wheel would remain true.
5. It was experienced builders also who gravely compelled us to tie and solder our spokes, to 'soft-spoke' for comfort, and to vary our spoking patterns to fine-tune our ride. Lets let sense come before experience. Edges have rounded off aluminium nipples for me in the field when I've had to use a borrowed wrench to fix a bent wheel, and it all just didn't seem worth it. My (hopefully balanced) points to the original poster still stand.
Oct 15, 2001 5:47 AM
|Have to kind of agree with you. The max spoke tension is a rim-section function and not a spoke function. Alloy nipples on a DT Revo (or Snapim Laser) will be a problem - especially on the R/Rear where you want max permissible tension cos you will have to tension higher than the heavier spokes (Comp or Race) to compensate for the added overload flexion of the thinner spokes. The weight saving isn't worth the long-term hassle. Anyway, the biggest problem with alloy nipples isn't between spoke and nipple - it's between rim and nipple if both are alloy.|
|Bad weather with alloy nipples||Timo Vennonen|
Oct 16, 2001 4:29 AM
|If you plan riding your new wheels in murky weather, I'd stay with the brass nipples. In my experience (as a user, not a builder) the alloy nipples tend to react with salt and other stuff, rendering the spoke/nipple interface impossible to adjust.|
Oct 18, 2001 5:50 PM
|Most people that are into alloy nipples get over it sooner or later for that very reason. Took a set of used wheels in trade and had to cut all the spokes - the alloy nipples had corroded and the rims were hammered. I knew this at the time - the only thing I wanted was the DA hubs, which were fine.|
|re: Custom Wheel Questions||aquaman|
Oct 15, 2001 5:47 PM
|A bit of history re: my post: I had wheels built this spring using Revo spokes, alloy nipples, Open Pro rims. I had the wheel trued once by original builder, then twice by LBS, then an emergency truing of front wheel after a truck-meets-bike experience. The emergency mechanic, who seemed quite knowledgeable (Tahoe Sports Ltd.), told me that the spoke tension was very high and he feared that the nipples may fail. I was v. surprised because the builder told me that Revo spokes are built at a lower tension than other spokes. The builder also said that any truing should be done by a LBS with experience with Revo spokes.
So--I'm wondering if the builder was full of bull about lower tensions with Revos, and/or if LBS wound the tensions up too far. After the wreck with truck, I was advised to have wheel rebuilt because the rim was so tacoed. After the great (and much appreciated) responses to the posts, I'm considering using brass nipples with non-Revo DB spokes so that I won't have to worry so much about who trues the wheels. Any strong feelings otherwise? Thanks!!
Oct 16, 2001 4:11 AM
|Your original wheelbuilder probably never did his job properly. You make no mention of your weight, requirements etc, but there is nothing inherently wrong with Revo's (Laser's). They are just a thinner bolt. Spokes and spoking patterns are not meant to provide you with some form of suspension. They simply lace a rim to a hub.
On a flat road the spokes hold the integrity of the wheel. When you hit a bump, the top spoke (and the ones on either side) take up the greatest momentary radial overload as the rim flexes. The greater the number of spokes, the tighter the tension or the heavier the spoke, the better that overload is shared by the affected (and other) spokes.
Thinner spokes flex more with overload. They thus need a higher tension to create greater preload and hence less flex (and so better load sharing) - to prevent spoke breakage caused primarily by that load/unload movement at the elbow. Weight saving on a wheel is always an iffy proposition. The best 'standing' wheels I've ever encountered were built by a old wheelbuilder in Ghent (Belgium) using Open Pro's on DA hubs with Sapim Race spokes (2.0/1.8/2.0 - 3 cross) with head washers and brass nipples. They have needed little truing in 8 yrs of abuse and are about thru on the brake surfaces now. All the alloy nippled/lightweight spoked wheels I've built/owned are a pale shadow and a maintenance nightmare by comparison. If you are a wheelbuilder or sponsored rider go Revo/Alloy and check wheels weekly. If not, overkill. Speed is still more in the legs.
|the old can of worms is open again...||Jofa|
Oct 16, 2001 8:01 AM
|A bike wheel is a prestressed structure and functions differently than the static model you describe. It's not the top spokes which support the wheel by a tension increase, but the bottom spokes which support it, by decreasing their tension: they function in compression, which might seem a little odd but is nevertheless the case. If you're doubtful of this proposition, you can prove it easily: pluck spokes at the top and bottom of a wheel, before and after it is loaded (have a weighty friend sit on the bike). The bottom spokes will have detensioned a little, no others will have changed.
Jobst Brandt describes these processes in detail, in effect and reason, in The Bicycle Wheel, and has done so elsewhere, on the web... a search may turn something up.
Because spoke tension only decreases in use, the ideal starting tension is as high as possible for all spokes (allowing a little breathing space for something to get caught in the spokes... about 90-95% is best).
To the previous poster- your mechanic is wrong in one key respect: his belief that high tension will cause nipples to fail. It is the cyclic loading as spokes are unloaded at the bottom of the wheel and then returned to full tension as they pass it that causes fatigue failure (more commonly, in the rim surrounding the sockets)... high tension makes no difference, and is, as I have said, ideal.
|You are wrong!||cyclequip|
Oct 17, 2001 3:51 AM
|You are correct in stating that a wheel is a prestressed structure, but it's prestressed design comes about in response to the real-world problems of dealing with momentary radial overloads - that of overload-sharing.
Brandt's proposition that the bottom spokes somehow 'support the wheel' by detensioning, has been countered by a number of others (see Gerd Schraner).
The AXLE is loaded downward by placing a rider on the bike, effectively spreading the load over the upper (hanging)spokes. The lower spokes cannot 'support' the wheel - the nipples press against nothing!!! So how can they magically 'compress'???
Your proposition that spoke tension only decreases in use can easily be proven false - try radially spoking a set of wheels with the spokes nice and loose. Put them on a bike and get a heavy friend to sit on the bike. Guess what - the top spokes increase in tension!! You can hear it when you pluck them.
Don't confuse this with the inability to hear minute tone changes in highly tensioned spokes sharing an overload over a number of spokes (the reason you can't hear higher pitch in hanging spokes in your example).
The lower tension in bottom spokes means lower load - hence less 'support' and more movement in the spoke. I'll not confuse this with the proposition that the detensioning process is the one which fatigues the spoke metal (again- commonly in the elbow area where the movement is most pronounced). Movement in the elbow area causes breakage - why non-drive rear wheel spokes fail most commonly.
So your statement that it's better to have a higher starting tension because load only decreases is exposed as false. In truth it's actually better to have a high tension to start with because this spreads load over more spokes in moments of overload and limits movement and hence breakage.
Your proposition that spoke tension has no bearing on spoke failure is NONSENSE!!! Gerd Schraner lists insufficient spoke tension as one of the PRIMARY CAUSES OF SPOKE FAILURE. Lace as many 'soft spoked' wheelsets as any starting wheelbuilder has before you stop because of rapid spoke failure. Then lace to the limit of nipple deformation(what is your 'breathing space'/90-95% - a new reading on the tensiometer?) - and make wheels that 'stand'.
Oct 17, 2001 10:16 AM
|Your proposition of the loosely spoked wheel is no longer a prestressed structure, and shouldn't be expected to behave like one. Prestress it by tightening the spokes, so it is like the ones we all ride everyday, and you will find that what I wrote is true. Radial spoking makes no functional difference in this respect except to allow each spoke to ring more clearly.
Your exaltation at noticing that the nipple isn't supported against compression, and that the spoke cannot therefore work in compression, shows that you haven't understood what is happening here. The spoke is stressed in tension and under loads experiences a decrease in this tension. Only the bottom, loaded, spokes experience any change. From the context of the wheel, and in any meaningful sense, this is compression. The process is detailed lucidly and efficiently by JB in his book: if you don't have it, I'm sure you could find the same information on the web... it is hotly discussed regularly.
My figure of 90-95 is a percentage of maximum spoke tension. This is the point at which the wheel collapses into a saddle shape, with very minor provocation. A half-turn or so back from this is ideal. No tensiometer could tell you this, though one will greatly aid you in equalising tensions.
The less Gerd Shraner has to say on this subject, the better, in my opinion. And myself: this could obviously turn into a bat and ball game, as it has done so many times, in bike shops, cafes, and the web- I don't intend to do it all again. The information is out there, for you and others (if anybody is interested in such esoteric stuff). The specifics of JB's elucidation of the structure of the bicycle wheel are generally accepted now, though it can still be tricky to visualise for some. Read the book: it's nicely written and should make it clear.
|I am glad||muncher|
Oct 18, 2001 4:10 AM
|That someone could be bothered to put that down on paper - there have been lots of posts on this subject, and sooner or later they all seem to come down to the falacy that the bottom spokes are "in compression", which arises when people confuse being under less extension, with compression. That and, of course, quoting endless slices of JB at every turn, as if "The Bicycle Wheel" was handed down just ahead of the 10 Commandments. Good for you - let's hope we can save a few hours of future threadwriting time now - (don't hold your breath)...|
|Foolish consistency||Kerry Irons|
Oct 18, 2001 5:20 PM
|The "less tension = compression" argument is one I have heard so many times I want to puke. It either comes from people who are so anal retentive about the sign (plus or minus) of a term in an equation that they forget the real world meaning of a term, or those just trying to confuse the argument and show some sort of "inside knowledge" that the rest of us don't have. Less tension is just that, not compression. JB sometimes just likes to hear himself talk.|
|Kerry's nailed it.||Leisure|
Oct 19, 2001 4:59 AM
|This discussion has less to do with the truth than winning the argument for a certain party in this conversation. It's actually kind of entertaining, but don't anyone let it get to you.|
|re: Custom Wheel Questions||FASRNU|
Oct 16, 2001 10:11 PM
|Have a custom set of wheels made for you,specific to the roads you ride,type of riding,and your own size and weight! Check out Youngwheels.com and have Joe Young build a set for you. He built me a set of 32 spoke Mavic CXP33 with Hugi 240 hubs they are awesome for training and Race!!!I am 6'5" and 213 lbs riding the mountains of Colorado.|
|Common sense and sanity.||nee Spoke Wrench|
Oct 17, 2001 8:24 AM
|I think tht theories of spoke tension and real life often vary by quite a bit.
First of all, a spoke tensiometer DOES NOT measure spoke tension. What it measures is how far a standard force will bend the spoke wire. The more tension on the spoke, the less it bends. The skinnier the wire, the more it bends. At the same spoke tension, a thinner gauge spoke will register a significantly higher number on the tensiometer. You have to factor in the gauge of the wire to infer the actual spoke tension.
After you figure out what the actual spoke tension is. What should it be? I've seen rim damage in a variety of forms that would lead me to believe the spoke tension was too high for that rim: cracks along the spoke bed and brake marks that line up with every spoke for example. What I've never seen is some spec. to tell me how much tension a rim can take either as maximum per spoke or a total for the whole wheel. My belief is that rims vary considerably regarding how much tension they will tolerate. Neither have I seen a spec. to tell me what the maximum tension for a spoke/nipple interface is either. I assume brass nipples will be better than aluminum.
For practical purposes, I find that the friction between the nipple and the rim limits how much tension I can build into a wheel. Alloy nipples tend to round out sooner that brass nipples, so they have to get less tension.
I use a Wheelsmith tensiometer on every spoke when I build a wheel. The only thing I use it for, however, is to make sure that the tension on each spoke is as equal to its fellows as possible. I use the SWAG method to determine how much tension to use.
I find it necessary to hold Revolution spokes to prevent spoke wind-up as I true and tension the wheel. Not being very careful with this step (which is a major pain) is going to result in an unreliable wheel. Consequently, I'm going to charge the customer more money to either build or true a wheel using Revolutions.
According to QBC, using Revolution 14/17 spokes and alloy nippes will save about 35 grams per wheel (32 spoke) over DT Competion 14/15 spokes and grass nipples. Are the lighter components worth it? I'd say yes if you are looking for the last increment of performance, no if reliability is your topmost concern.
|How do you hold Revo's so they don't wind up?||JS|
Oct 17, 2001 9:22 AM
|I cannot find a reliable method of doing this. I now use an ink pen to mark each spoke so I can visually watch it and using a quick motion I can usually get the nipple to move without the spoke turning, it can be a pain.|
|How do you hold Revo's so they don't wind up? - Ksyriums too?||grease monkey|
Oct 19, 2001 5:09 AM
|I was wondering this about special k's.
I was using a crescent wrench w/ a rag on the bladed spokes. anyone have a better way?