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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!

heltonbiker
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  • Just going to Google Image search and typing in "broken hub flange radial spokes" send me to this page (http://forums.roadbikereview.com/fixed-single-speed/would-someone-perhaps-help-noobie-out-295472.html) 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
  • My very first home-built wheel was a radially-laced front on a Shimano LX hub with straight gauge spokes (before I really knew what butted spokes were.) I spent more time replacing spokes than riding on it, and I'm still not great at building wheels. (Also: http://www.global-flat.com/smf/index.php?topic=41309.0 this link has a great picture.) – WTHarper 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
  • @heltonbiker I am! I read Jobst Brandt's The Bicycle Wheel, but just haven't built many (my grand total is 4.5 - one wheel just got away from me, so I sold the hub. I also don't own a truing stand, which doesn't help.) I truly appreciate well built wheels, though! – WTHarper Dec 19 '12 at 19:05
  • This site isn't sufficiently big such that you'll get more than a couple more anecdotal stories, which probably won't sway you more than the existing stories on the other forums which haven't seem to have swayed you yet. What is to be gained by using a radial spoke pattern? If it's really that important, there are hubs out there that are specifically designed to be laced radially. I'm guessing that the manufacturers have stress tested their hubs and recommend against it because there's a good chance it could break. Otherwise it would be another marketing point they could put on the packaging. – Kibbee Dec 19 '12 at 19:06
  • @WTHarper I have read Brandt's book, too, but I found it too speculative and certainly not helpful for anyone interested in practic issues about actually BUILDING a wheel, which Schraner's book certainly is. – heltonbiker Dec 19 '12 at 19:17
  • @Kibbee I am sensible about this question deserving to be here or not, and if people choose to close it, no problem. The reasons to radially lace a front, rim-brake wheel are many, and I'll tell mine: 1) Way easier to clean the spokes; 2) It makes sense, since the front hub doesn't transmit torque; 3) It's pretty and simple; 4) It's way easier to assemble and service (replace spokes) than a cross-laced wheel. If it wasn't for this manufacturer issue, I'd say radial pattern should be the obvious pattern of choice for front, rim-brake wheels. – heltonbiker Dec 19 '12 at 19:24
  • @heltonbiker He is an engineer, after all. Sheldon Brown has a nice Jobst Brandt FAQ (http://sheldonbrown.com/brandt/index.html) and also more indexed engineering stuff at (http://yarchive.net/bike/index.html) – WTHarper Dec 19 '12 at 19:31
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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
  • Not really related, but it's curious how a question with so many comments keeps without any answer. I'd be glad to upvote the last two if they were answers, and most probably I'm gonna post one myself after all this new information has settled. – heltonbiker Dec 20 '12 at 18:32
  • For what it is worth I recently replaced a Mavic Open Pro wheel. It was about 5 years old has about 10,000 miles on it. It was radially laced. It hit car door while going about 22mph. The wheel folded like a taco. About half the spokes bent, 5 or 6 nipples pulled through the rim. Not one hub spoke hole was damaged. If that wasn't enough abuse to damage a hub I don't think anything else would. – mikes Dec 25 '12 at 12:32
  • @heltonbiker: I think this is a bit of a tough question to find definitive sources. Offering a bounty can help. I've put 250 rep up, maybe you should offer to double that with another bounty after this one closes? – freiheit Jan 04 '13 at 22:38
  • @freiheit I appreciate your suggestion, but I think I'd rather write an answer soon, summarizing the discussion. Of course, I won't accept it, and I could gladly accept any good answer that comes in the future. But I'll consider the bounty, anyway! – heltonbiker Jan 05 '13 at 00:03

1 Answers1

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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.

zenbike
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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 07 '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 07 '13 at 18:14