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Most hub manufacturers forbid lacing spokes radially, mostly because there is less material in the radial direction away from a flange hole than in the standard 3-cross, tangential lacing.

(UPDATE: as it appears, the actual breaking point is the material betwen consecutive spoke holes in the flange, the spoke holes acting like a perforated-toilet-paper effect...)

I have previously laced a Shimano front hub radially and rode it a lot, and nothing happened. Some friends of mine have done the same in the past (allways front wheel, always XC mountainbike), and nothing happened either. Currently, I have just laced another hub radially, and I am pretty sure nothing evil will happen, but still there is some discomfort for doing a theoretically Wrong Thing.

So, I want to ask you about FACTS (disregarding what manufacturers say): is there any WITNESSED (by yourselves, not internet stories) evidence that radially spoked FRONT hub flanges have ACTUALLY BREAKED? Any photos, stories, or preferrably shop experience?

(ANOTHER UPDATE: as already mentioned, there are a lot of photos and stories about hub flanges broken with radially laced spokes. But, as it turns out, if the search terms contain only "broken hub flange", and not "radial", there are also a lot of photos and stories of broken flanges with standard cross-laced spokes. This makes me think of flanges braeaking for a lot of possible causes, but when this happens with radial spokes, it draws more attention and provokes some confusion bias about causality, relating the failure to the spoke pattern instead of other form of abuse or material wearing.)

Thanks very much!

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Just going to Google Image search and typing in "broken hub flange radial spokes" send me to this page (forums.roadbikereview.com/fixed-single-speed/…) if you scroll down to the bottom, You'll clearly see and image where this has happened. I'm not sure how common it is, but there's a reason that the manufacturer puts that warning on the hubs. I don't have my own story, but it's easy enough to do a Google search and find that there are enough stories out there that I wouldn't do it. What do you hope to achieve by doing this? –  Kibbee Dec 19 '12 at 18:02
    
@Kibbee In the same beaten forum threads that are easily found, as you have seen, some people suggest that this urban legend raised by oversharing the same relatively few stories and photos over and over. So I asked here, because sooner or later this site should have this (in)famous question, and because I think any discussion here should be more up-to-date and trustworthy. Anyway, I am aware of the stories and the risks concerning radial spokes, I am going to do it anyway, but I enjoy having more, consistent information about it. –  heltonbiker Dec 19 '12 at 18:08
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@WTHarper in case you are still interested in wheelbuilding, there's a life-changing, definitive bible book about this, in my opinion: "The Art of Wheelbuilding", by Gerd Schraner. –  heltonbiker Dec 19 '12 at 18:49
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Certainly there are now a lot of radially-laced front wheels in use, and there is not a flood of reports on their failure. And I've only read (from several "credible" sources) stories of this happening (the perforated separation) -- never experienced it personally or seen an hub damaged in this way. While I'm no big fan of radial lacing, I guess I'd say that this reason for avoiding the technique is not particularly high on the list. –  Daniel R Hicks Dec 19 '12 at 20:25
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Most of my front wheels are radial laced, many of my rear wheels are radial on non-drive. About 2/3 of these are wheels that I've built. All are road or cross (and I've beat the crap out of the cross) and I've had no problems. –  Ken Hiatt Dec 20 '12 at 18:21
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1 Answer

While it is possible for a hub flange to fail due to radial lacing, if the wheel is built properly, to proper tension, it doesn't happen, generally.

The reason it happens is because the amount of material between the spoke head and the edge of the flange is least when the spoke is pulling directly to the edge. Under normal usage, the flange has more than enough strength, even when laced radially.

However, if the wheel is laced with too much tension, or if the wheel is placed under abnormal stress, like when used for braking on a fixed gear, then the hub flange is more likely to fail when radially laced, than when laced with a proper crossing pattern.

It can still fail, even when crossed, but it is far more likely when laced radially, due to the smaller amount of material, and more direct tension on the flange.

I have used radially laced wheels, mainly for BMX racing as a kid, I have had only one failure of a hub flange, though, and that was on a Bontrager Race XXX Lite rear wheel in 2003. That wheel uses a radially laced, paired spoke pattern, which I do believe contributed to the failure. They are also excessively high tension wheels, due to the low spoke count, and I think it took both the radial pattern, and the excessively high tension to cause the flange to break.

I hope that helps.

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Thanks for the answer, but I have some points of confusion: 1) You mention the amount of material between the flange edge and the spoke head, but the most common failure mode seems to be between flange holes, considering the photos around. 2) Radial lacing is never used in traction wheels (at least shouldn't, at least not both sides), and I think even the most brave hipsters wouldn't lace the rear wheel radially. –  heltonbiker Jan 7 '13 at 14:07
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There are many wheels which are laced radially on the rear, like the bontrager set mentioned above. I do not recommend it, nor do I think it is a correct or safe way to build a wheel, but then, I wouldn't build any radial wheel, anymore. The photos on the link mentioned above are the same bontrager hubs. That type of failure is typical from what I've seen of the over tensioned wheel failure they are prone to. There also was an issue with a batch of Bont hubs with defective material or design. As for the width of the flange, that's just common sense. Less material equals less strength. –  zenbike Jan 7 '13 at 18:14
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