I must have some luck! I have had two campagnolo rear hubs fail on me in the last six months! The first was a 70s vintage campy record hub with about 5000miles (by me, and who knows how many before that!). The second was a hub sold to me as a grand-sport but more likely an 80s vintage chorus (going by velobase). The flanges failed on both of these (see pics below).

Each time I heard a *ping* and had a sudden loss of wheel true as the wheel rubbed the chainstay. I was going slowly enough each time to avoid a spill (coming away from an intersection).

I have two questions: 1) Is this just a coincidence, or is there an underlying common cause to these two failures? 2) How, and how quickly do I have to unlace the rims to keep them from being permanently damaged?

Chorus:
Record:

Hmmm. No knowledge or experience but it is interesting that they both failed where the spokes cross.

Too much tension perhaps. What gauge or those spokes? Campy record hub flange failures are very rare; it usually only happens on radial spoke wheels and that sort of thing.

While not exactly common it does happen. I've seen only a few in my 45 years but read of it every so often in the forums I follow. Andy.

I've broken two NR large flange track hubs, using them on the road. I have heard that wasn't unusual. (I still cannot figure out what about road riding makes such a difference that I can break a hub designed to be ridden hard by the most massive quads in bike racing with my 150 pounds and skinny legs.)

Ben

It should be noted that modern wheelbuilders use substantially higher spoke tension than was once normal. I don't want to get into a discussion of that right now, but IMHO overtension is the most probable cause.

Other than that could be anything: over loading, corrosion, bad luck, under tension even. I've ridden probaby 100,000 miles on campy hubs and never broke one.

I'll also mention that at one time it was understood that Campy hubs were drilled for 15g spokes. Having said that almost every one I have come across (personal and professional) are laced with 14g spokes, at least in the elbow end. Andy

I had one fail years ago, looks pretty much exactly like the photo on the right (I couldn't throw it away, and still have it on my desk at work). I had a "chain suck" episode at some point -- can't remember how long before the failure -- and attributed the broken flange to that.

Not to argue with any of the hypotheses given, but let me propose one more. Not saying it's better, but it is another one.

I recall that when re-lacing a hub, it is important to run the new spokes for each direction in the same holes and with the same crossings as was used for the original wheel build. Not to do so could add new stresses at the hole in directions that the once-distorted (cold-set, actually!) metal around the spoke drillings is not able to handle. A not-so-careful re-lacing could have resulted in holes running spokes wrong.

I don't know where i read that, or what I may have been smoking at the time.

Hello, Charles! Long time no see!

I always do that (match the old spoke pattern on the hub) if I can and figure I may be shortening the life og the flange if I don't.

Ben

So we may have been smoking the same thing at that moment in history!

I've heard that "relace the same way" too; but it wasn't the problem with my Record hub that failed; wheel was the original build.

Yes, I've had it happen too. Riding 50 year old aluminum parts of unknown mileage is always going to be crap shoot. Replicating the original spoking pattern will reduce the probability of failure but not eliminate it.

I broke a Specialized hub like that, only it took a bigger section, with 4 or 5 spokes. I blamed it on an expansion joint, crossing a freeway bridge, but I'm not entirely sure. It was still very rideable, believe it or not, and I didn't identify the problem immediately, just had a weird noise, lol.

ding ding ding That's why I laugh when peeps be like 'I tensioned to X with my tension gauge' Um, so what.

"so what" is that with increasing tension differences between drive and non drive side spokes to be able to attain sufficient non drive side tension the drive side tension is getting really high. This is one reason why there's so much talk about tension gauges lately. Add to that the reduction of spoke count and the need to up the remaining spokes' tensions to align even stiffer rims and it's no wonder that old hubs suffer from flange pull apart. Andy

If the OP bought the hubs used, it's possible that they were previously laced racial and weaken the flange. In general, when building wheels with used hubs, I try to follow the previous build's lace pattern (as evidenced by marks left on the flange by the spokes). Even if the previous build was not radial, not following the previous build's lace pattern may result in a weaker wheel.

Lowering the spoke count and increasing the number of cogs on the rear cluster are what makes modern wheels require higher and more even spoke tension. Personally, I avoid using more than six cogs on vintage hubs.

Thanks everyone for the speculation and tales of commiseration. To add a little clarification, I've only every had two wheel sets on this bike, the one I bought it with (5000mi ago) and the one I bought off of ebay to replace the first failure. I did not build these wheelsets, but the spokes look to have only every been laced once--as far as I know. I'm going to chalk this up as 'one of those things' and 'just dumb luck'.

Do I need to de-lace the broken hubs to save the rims?

I'm not sure I'm following the question, but if you're asking are the rims being damaged over time being left laced and tensioned with the two missing spokes, no, very unlikely (aSSuming you're not riding it in this condition ). Any damage to the rims (i.e. permanent warping) was already done when the hub broke, and during the presumably short period between that event and when your ride came to a halt.

On one of the hubs, I suspect damage to the shell through corrosion. Aluminum is especially vulnerable to surface irregularities that act as seeds, forming micro cracks, which propagate. This is very common where salt in the environment attacks a part that's under high loads.

The other hub seems to be in much better shape. So it's either bad luck, or excess loading from stout spokes under high tension.

Keep in mind that tension is tension, so the spoke gauge isn't a factorfor static loads. However the spoke's gauge can have an effect on the peak tensions achieved under dynamic loads. So, a plain gauge spoke may be suffering higher peak tension loads on bad roads, and that higher stress can accelerate fatigue.

In both scenarios above, I'm not stating a cause or even an opinion, I'm simply pointing out possibilities to explore.

My reference to spoke hole size wasn't about spoke gage and spoke tensions but about the spoke hole becoming more affected by a slightly larger spoke (2mm VS 1.8mm) being used. The larger spoke likely produces greater hole deformation, elbow indentation and resulting micro cracking.


Only an opinion with no facts to back it up. Andy

Good to know! This is precisely what I was asking--the rims are now 'untrue' because of the missing spokes, and I was wondering if the currently unequal tension would continue to affect the rim before I get the chance to unlace it in a week or two.

Yes, it was a short ride indeed. After in the incident, I carried the bike up the hill, and walked it a half mile. I did ride it the last couple of blocks figuring I couldn't do worse to the hubs. One day I'd like to re-use the rims.

But it's ver easy to take two turns out at one turn at a time - why leave it all twisted? And make sure to remove the freewheel . Ive found in most my five and six freewheels that I can take a fat washer at least and put it non drive side. Most hubs leave a seven speed compact or six with lots of space for the bottom cog from dropout rub. Every Japanese bicycle Fuji MiyTa Centurion I do this to the hubs and also toss the crap bb they seem to always use ( stud mount )


UOTE=old's'cool;19543143]I'twistedm not sure I'm following the question, but if you're asking are the rims being damaged over time being left laced and tensioned with the two missing spokes, no, very unlikely (aSSuming you're not riding it in this condition ). Any damage to the rims (i.e. permanent warping) was already done when the hub broke, and during the presumably short period between that event and when your ride came to a halt.[/QUOTE]

I never had a cracked hub flange in over 40 years of cycling, and I've taken a few pretty good spills as my original brake levers, pedal ends and even the lower derailleur bolts will attest. But I've always laced my own wheels and with the used Campy hubs I've purchased, I've been careful to not use any that showed any signed of being radially spoked. For the record, I never encountered a radially spoked Campy R / NR / SR hub, and I only purchased hubs that looked well cared for. I did get a broken axle once though.

When lacing up my wheelsets, I try to run the spokes in the direction that was used before, except for a couple that were originally laced wrong. I laced them correctly and have had no problems.

Refer to the late Sheldon Brown's page on wheelbuilding for details on wheelbuilding and lacing:

Wheelbuilding

Sheldon was one crazy dude, but he know about bikes.

One of those hubs looks much the worse for wear and oxidation. That could have contributed to the failure. Either that or there was an extreme shock to the wheel.