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Theory: PSI & spoke life

Old 05-30-18, 02:10 PM
  #51  
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A little perspective

Sometimes this discussion sounds like snobbery, because there is an implication that only bicycle wizards should build wheels because we have the spells like "proper spoke bedding technique" that the mortals do not. But that's really not what I'm trying to get across.

In the '90s there was a hot new tubeset that came out called Carpenter Aer-Met. I went to the CABDA trade show, and the Carpenter Steel people had a booth, as did some custom frame makers who happened to use Aer-Met. I talked to the Carpenter people and looked at their handouts - the tubing had great specifications - after it was post-weld heat treated. In other words, Aer-Met was really strong despite the thin walls because welded sections were supposed to be heat treated after the frame was welded (something common on aluminum frames but not normal for steel bikes).

Then I was talking to one of these small frame builders using Aer-Met and they had a really light MTB frame. So I asked them "How big a heat treatment oven do you have?", because I was curious if they were treating them one at a time or in batches (some heat treatments take several hours). They didn't have an oven, and were not heat treating the completed frames as specified by Carpenter. So their ultra thin frame tubes where no stronger than standard 4130 of the same thickness.


The point being, doing something the right way isn't some special skill or formula, it is just doing the proper steps to make something. Spoke bedding is a proper step in wheel building, because elbows are left with shallow bends that work correctly with inside spokes, but need to be bent further to suit the angles of the outside spokes. If you don't do that step, you're just like the guys making Aer-Met frames without heat treating - you're building a structure that is not to spec and is unfinished. Companies that make cheap machine built wheels aren't concerned with their reputation for the wheels lasting 20,000 miles, so they skip this step because it would make wheel machines much more complex and expensive. But anyone building wheels by hand can bed the spokes - it takes no tools and only a few seconds of extra time.
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Old 05-31-18, 10:06 AM
  #52  
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Originally Posted by Kontact View Post
If that were true, then a 10 pound weight with a 1"x1" bottom would put more pressure on a scale than a 100 pound weight with a 10"x 10" bottom:

1x1= 1 square inch. 10 pounds on 1 square inch = 10 PSI
10x10 = 100 square inches. 100 pounds on 100 square inches = 1 PSI

But the 100 pound weight actually puts 90 more pounds of total pressure on the scale. Or rim, or whatever.
Wrong analogy. A tire pushing around a circle, not down. A smaller tire at a higher pressure is going to splay the rim outward more which will reduce the spoke tension.


Originally Posted by Kontact View Post
I could call him, but I'll just quote Ric instead:

If spoke breakage is a much bigger issue of "cost conscious wheels", why would that be? Are cheap wheels built with lighter rims or cheaper spokes? No, cheap wheels use heavier rims and he's already assuming that the wheels are using DT quality spokes by suggesting substituting a different gauge rather than better quality.

The only real difference between "cost conscious wheels" and custom wheels is how they are built. Custom wheels (the kind you are building for yourself), feature bedded spoke elbows, even tension and stress relief that machine built "cost conscious wheels" do not. That's the difference that he's talking.

If he was talking about low spoke count wheels or lightweight rim wheels, then we might assume something other than build quality is the issue. But it isn't - this is Ric's bandaid for less quality labor, not lower quality specifications.
You kind of glossed over this part of the quote

...(also for many high performance wheels as well).
I don't think he is calling for spokes like the Alpine III to be used in machine built wheels...although that would go a long way towards making them more durable. Nor do I read his article as saying "do this because it will make poorly made wheels better"...although, again, it would go a long way towards making wheels better. The thrust of his article is that these spokes make for stronger, more durable wheels. For example, consider these two quotes from the main body of the article

Begin using beefy elbow spokes tomorrow! Tell other builders, mechanics, and product managers at once. Convince spoke companies to NOT drop these gauges the way they dropped many 15g models. Slow sales leads to the end of any product.

Pat yourself on the back for being a wheel guru; knowing cheap tricks, clever solutions, overlooked options; and spreading the word. No flailing around blindly, you’re a confident expert. Prove it by putting beefy elbow spokes to work.
and from the comments

OK, how about the others who are on short budgets or expect ridiculous long life from their equipment? These are not competitors. They outnumber competitors 10000:1. Their needs are well served with beefy elbows, the point of this post.
"Cost conscious" can mean cheap but it can also mean economical, as in wanting wheels to last a very long time.

Originally Posted by Kontact View Post
If you are producing wheels of lower labor quality, then by all means use a spoke with a thicker spoke elbow to make up for your work.
And, yet again, you miss the point. Yes, spokes with thicker elbows would make low quality wheels better. But they will also make well built wheels even better than they are now.
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Old 05-31-18, 10:12 AM
  #53  
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Originally Posted by Kontact View Post
He doesn't say that explicitly, in part because that would be throwing the market that he is trying to sell to under the bus.

But are you really unclear on just what "lower cost wheels" implies? I'm not going to re-write my previous post on the subject, but if you would like to quote and respond to it, please do.

The kind of wheels that people hand build are not "low cost wheels". They consist of name brand components and have labor costs greatly exceeding machine built wheels. Consumers and shops can't really buy those lower cost OEM rims, hubs and spokes used in the $100 wheelset.
Hjertberg doesn't say "lower cost wheels". He says "cost conscious wheels". That covers a lot of ground. I could buy several cheap wheels because I'm "cost conscious" or I could build one set of wheels that I expect to outlast several cheap wheels. With the latter, I might spend more money up front but in the long run I will save money because I don't have to buy more wheel sets. I'm conscious of the difference between the two.
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Old 05-31-18, 10:37 AM
  #54  
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Originally Posted by Kontact View Post
Specific to your question, modern hubs are made with 2.0 butts in mind. They are arguably the "natural" choice for building wheels, and they can be found butted, very butted or straight.
No, modern hubs aren't made with 2.0 mm butts in mind. They are made with 2.4mm holes so that the (approximately) 0.3mm rolled threads that add to the diameter of a 2.0mm wire used to make the spokes can pass through the hub. In a more perfect world, the hub's spoke holes would be closer to the diameter of the spoke head being used, i.e. 2.0mm for a "normal" spoke. One of the benefits of the 2.3mm spoke heads fill the hole better which makes for a tighter fit which is usually what you want in any fastener.

Originally Posted by Kontact View Post
2.3 butted spokes were developed by seeing what's the maximum thickness that can be crammed in a modern hub flange intended for 2.0 spokes. If the hole was 4mm, there would be someone marketing 4mm butted spokes, but the hole won't allow for more than 2.3, so that's what they are.
No, 2.3 mm spokes were developed to fit a need for a more durable spoke. DT Swiss made the spokes with 2.3mm heads because the heads fit in existing spoke holes in the hub flanges. They were smart enough to realize that they could make the spoke marginally thicker and get a greater return on the strength for very little penalty.

Originally Posted by Kontact View Post
For someone building wheels by hand, 2.3 butted spokes add weight and expense while making it more difficult to bed the spokes due to the extra stiff butt section - and bedding the spokes isn't just good for the spoke elbow but for the overall wheel since it is part of the stress relief process that prevents the need to re-true and re-tension the wheel after several initial rides.
You keep saying this but have nothing to back it up. Prove it! Show us how a spoke with a 2.3mm head isn't bedded properly. A wheel built with 2.3mm spokes doesn't need any more stress relief nor does it need more tuning after initial rides than any other spoke used

Originally Posted by Kontact View Post
So my objection is three part:
1. It makes it more difficult to build a wheel in the proper way, since a properly built wheel should have the elbows bent to bed them in.
2. It adds unnecessary cost and weight.
3. It serves to mask a wheel building problem. As Cyclomute has described previously, he's broken spoke elbows on wheels he's built, leading him to appreciate stronger elbows as a solution. But the majority of professional wheelbuilders seem to agree that breaking elbows (and spokes in general) is the result of a techinique problem, and not the result of 2.0 butts being inappropriately thin.
Again, show us how point 1 is valid. You just claim it. As for cost, yes, they are slightly more expensive but not excessively so. Hjertberg's article addresses the weight issue in that a triple butted spoke adds 7 grams to the wheel. That's not a lot of extra weight for a lot of extra durability.

As for point 3, that's just your opinion. Hjertberg doesn't seem to feel that way. My technique works well enough for my wife and daughter's wheels in that they don't break spokes. I outweigh them by a lot and I ride more aggressively. But once I went to triple butted spokes, spoke breakage for the same weight and riding style decreased dramatically. Maybe I learned more about wheel building or maybe the spokes do what they were designed to do. My money is on the latter because I use the same technique as you do taught to me...granted through print not personally...as you learned.

Originally Posted by Kontact View Post
So if you don't want to have a broken elbows, you can use the correct practices and you'll get long lasting, lighter weight wheels with 2.0 spokes and less effort.
OR - You can fail to bed your spokes, use thick elbows and end up with a wheel that goes out of true more easily, even if it doesn't have an elbow breakage problem.
Or you can be open minded and use the 2.3mm spokes to build even better wheels using "the correct practices" as Hjertberg is suggesting.

Or you can stick your head in the sand and say "Nope. Won't happen. I won't try anything new because that's the way I was taught."


Originally Posted by Kontact View Post
Are 2.3mm spokes stronger? Sure. And 5mm spokes would be that much stronger. Why not go to 10mm spokes and make sure everything is strong enough? While you're at it you can use 1000gram rims and 2mm thick steel frame tubing. But we don't do those things because bike components are supposed to be light and flexible, and 2.0 butted spokes are a time tested way to build super strong, light and lively feeling wheels.
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Old 05-31-18, 10:43 AM
  #55  
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Originally Posted by Kontact View Post
Sometimes this discussion sounds like snobbery, because there is an implication that only bicycle wizards should build wheels because we have the spells like "proper spoke bedding technique" that the mortals do not. But that's really not what I'm trying to get across.
That may not be what you want to get across but that exactly what imply all the time. I've told numerous times that I know what spoke bedding is and how to do it. I have done it on every single wheel set I've made since I read and used Hjertberg's Bicycling magazine article in 1986. It's not that hard to do nor to understand. I do it for the 2.3mm spokes I currently use. I don't see what I could do differently to get a different outcome that you continue to imply that I should be doing. "Build it better" only goes so far. In fact, I do "build it better" by using a stronger, more durable spoke.
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Old 05-31-18, 12:10 PM
  #56  
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Originally Posted by cyccommute View Post
Wrong analogy. A tire pushing around a circle, not down. A smaller tire at a higher pressure is going to splay the rim outward more which will reduce the spoke tension.
It is a bit frustrating to discuss such things when you don't seem to get what's happening on a basic level. The inflated tire is compressing the rim, pushing the rim inward, which reduces the spoke tension.

Originally Posted by cyccommute View Post
That may not be what you want to get across but that exactly what imply all the time. I've told numerous times that I know what spoke bedding is and how to do it. I have done it on every single wheel set I've made since I read and used Hjertberg's Bicycling magazine article in 1986. It's not that hard to do nor to understand. I do it for the 2.3mm spokes I currently use. I don't see what I could do differently to get a different outcome that you continue to imply that I should be doing. "Build it better" only goes so far. In fact, I do "build it better" by using a stronger, more durable spoke.

Round and round: Once again - professional wheel builders disagree with you, and you are basing an entire argument on Ric's suggestion that thick spokes are great for "cost conscious wheels", and trying to build an engineering philosophy out of that.

And I'm not implying anything - I'm being super explicit when I say that preventing elbow breakage is simply method, not magic.

Real world - spoke elbows don't break on correctly built wheels. They don't break on my wheels, Ergott's wheels, Vechio's wheels, etc. They simply don't break. So if the elbows are breaking on your wheels, there's something wrong, and it isn't the elbow thickness.


And if this forum didn't tend to scare off professionals because of exactly these sort of angry amateur antics, you'd have six other professional people telling you the exact same thing I have gone to such pains to explain. Try going on Paceline or velocipedesalon and letting those folks know that you have the 2.3mm solution to the elbow breakage problem they have - that conversation will be over in 2 minutes.

This sort of argument can only be prolonged in an environment where the pinnacle of expertise is the hobbyist and industry people are looked at with suspician. It is really too bad that this sort 2+2 argument make people with real expertise drop out and go to forums where conversations about bicycle mechanics aren't ruled by a mob. It's depressing and too bad bikeforums is so disparaging to tradespeople.

Last edited by Kontact; 05-31-18 at 12:35 PM.
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Old 05-31-18, 12:19 PM
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Originally Posted by Kontact View Post
It is a bit frustrating to discuss such things when you don't seem to get what's happening on a basic level. The inflated tire is compressing the rim, pushing the rim inward, which reduces the spoke tension.

.
Also, tubeless tires cause a bit of a larger spoke-tension drop than tubed tires... So wheels that might be borderline on NDS tension with a tubed tire are even worse off with tubeless.
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