Originally Posted by
bigfred
And, on this point, some will continue to disagree with you. State it as often as you like and in as many locations. You'll never convince those individuals that subscribe to the points made by folks like Park Tool:
"The recommended tension for spokes in bicycle wheels can be as low as 80 Kilograms force (Kfg) and as high as 230 Kilograms force. As a rule of thumb, it is best to set tension as high as the weakest link in the system will allow, which for a bicycle wheel is usually the rim. Therefore, to obtain a spoke tension recommendation for a specific wheel, it is best to contact the rim manufacturer."
The facts are: Heavy spokes allow higher tensions. Heavy spokes and higher tensions result in less elastic elongation. Less elastic elongation results in less lateral and radial flex of the rim. Lighter/weaker rims can't tolerate the high tensions that can be achieved with heavy spokes and provide less static resistance to radial flex. Heavy/stronger rims provide both more static resistance to radial flex and the ability to accomodate the higher spoke tension that heavier spokes are capable of maintaining. Hence, heavier/stronger rims can and do build into stronger wheels than lighter/weaker rims built up with the same hubs and spokes.
Heavier spokes do allow for
slightly more tension but that's not the reason that heavier spokes are used. Heavier spokes resist fatigue at the head of the spoke which is where a spoke is going to fail in almost all cases. Spokes are butted to get more strength a the head of the spoke where it is needed. The amount of tension that you can put on a rim with the spokes isn't limited by the spoke diameter. You can put enough tension on a 1.8mm unbutted spoke to pull the spoke through any aluminum rim before the spoke would fail.
Think of what people talk about when a wheel is failing. The number of questions that have been posted on these forums over the years about wheel failures is almost countless. Very, very few of them are about the rim failing. The typical question usually goes something like "I've broken x number of spokes, should I replace the wheels?" or the advice is usually "If you've broken x number of spokes, you should consider a wheel replacement." Also think about what advice you receive (or give) if someone wants a stronger wheel. Do you suggest a stronger rim or more spokes? I've never seen
anyone suggest fewer spokes and a "stronger" rim. Almost all the advice is for more spokes.
Here's an example: Let's choose the strongest rim I can think of...a steel 1.5" balloon tire rim off a cruiser. Now let's choose the lightest weight
steel spokes I can think of...DT Competitions that are 1.8/1.7/1.8mm. I'll only consider the rear wheel since that's the one that always has problems. I'll use a 130mm 10 speed hub and build the wheel in a radial nondrive/2 cross drive side pattern. And I'm going to use only 12 spokes. Is the wheel strong enough for a clyde? Would you want to ride it? It's got the most incredibly strong rim on the planet. Or would the wheel be much better with 36 spokes in the same pattern?
The aluminum of the rim
is a weak link but, for the most part, wider, heavier rims are just wider and heavier. They aren't necessarily stronger because, in the end, spoke breakage is the deciding factor on wheel strength.