Spokes keep breaking - bad hub or bad build?

Question

Background information

A bit of background information (I'll try keep it brief): Last year I bought an old but unused bike, 5 speeds with internal gearing.

Apparently the shop bought a lot of bikes somewhere in the 90's (not sure), but never got around to selling them. When I bought it, it was wrapped in plastic, had been stored in the shop's stock house for about 20 years and free of corrosion.

I'm about 95 kilos, thread quite hard but rides exclusive to paved bike paths. The original, 20(?) year-old wheel lasted me a year with no problems. The front wheel is still fine and true.

Spokes breaking - and getting replaced

After a little under a year, I suddenly noticed that a few spokes had broken. On closer inspection, quite a few were too loose. Should have noticed sooner but didn't.

I took it to a shop, where they advised me to have the wheel rebuilt which I paid them to do. The gearing being internal, the new rims and spokes were built on the existing hub.

After just two weeks, the back wheel suddenly began to feel wobbly on my way to work. As careful as I could, I drove the bike back to the shop. Almost all spokes were terribly loose.

They retensioned the wheel free of charge (of course) and sent me on my way. The following weeks, I periodically checked that all spokes were still tensioned.

2,5 months later, I noticed three of the spokes were broken close to the hub. Went back to the shop and had the spokes replaced (free or charge). 1 month later I noticed 2 broken spokes and had those replaced as well. They seemed less eager to keep fixing the wheel free of charge, and when I asked why the spokes kept breaking, the guy muttered something about the hub holes maybe had burrs due to wear.

Now, a few weeks later, I find another spoke broken.

My gut tells me this all stems from a bad build, that quickly lost tension and thus damaged the spokes. I find the explanation about a worn hub a bit far fetched, but I don't have the knowledge to dismiss the theory.

Questions

Is there any way this is not the shop's fault? - A bad build? Cheap spokes? Improperly tensioned?

Given the wheel's history, is there any point in keep replacing spokes, a couple at a time, or should I get the wheel rebuilt (preferably at the shop's expense)?

Could the hub in any way be to blame for this?

Thank you!

Update Oct 24th

I've been trying to get in touch with the manager of the shop throughout the week. Failed again to reach him this morning, so I figured I'd have a chat about my problem with one of the guys on the floor.

Tried to get him to provide at least a theory of why my spokes keep breaking, but not much came out of it really. He mentioned that he've seen, on rare occasaions, that a worn hub could cut the spokes (could be the same guy as I spoke to last time).

I'll check the hubs as soon as possible, as @Daniel R Hicks suggested. Due to plumbing work in our appartment, I haven't been home or able to check my bike all week.

If I don't see any indicatations that the spokes were put in the wrong way, I'm going to follow the advice most of you have, and take my bike to another shop for advice and repair.

Thanks so far! - I'll update you after I've payed the other shop a visit.

Update Nov 3rd

Took the bike to the other shop, told them the story. Let them decide to replace the broken spoke or them all.

They decided to replace just the broken spoke with a DT spoke (what ever that means). They also trued the wheel, which had gotten a slight "eggy" shape.

My fingers are crossed that this wheel will last now.

Once again, thank you all for your input!

Anecdotal Update

In case anyone follows... Since the last repair at the other shop, the wheel kept being in good shape. Finally, my spokes stayed tensioned, wheels stiff and true - the long struggle was finally over. Alas, the joy didn't even last a month...

Going home from a company party, I returned to my bike I parked at the train station, only to find out that some punk kids had apparently tossed it to the ground, and jumped both wheels badly out of shape. Front wheel had to be replaced and back wheel was in desperate need for a trueing. sigh

Sorry for the melodrama, just thought I'd update you the faith of my bike ;-).

Answer 1

A wheel is only as strong as the tension on the spokes. If the wheel was loose for any significant length of time before you noticed it, the spokes will fatigue very quickly, because they are flexing through a range of motion which is not intended.

You are a big guy at 95 Kg, so this type of problem is not unusual (as am I). That means that you need to be especially wary of loose spokes and rapid detensioning of your wheels. Most "system" wheels have an 85-100 Kg bike and rider weight limit. It would be difficult to conclude that it is the the sole responsibility of the shop.

However, this is a recognized problem, and one your shop should have discussed with you prior to rebuilding the wheels. In addition, they should have prepared you to check and tune the wheels with greater frequency.

A break in "tune up" is normal and expected on a new wheel, after about 1 months riding, but it can come much faster for a heavy rider. If the wheel is ridden loose, the fatigue damage to the spokes can be permanent, and require rebuilding the wheels again.

This is not quite the fault of the shop, but it sounds as if they did not take the care and time to explain the necessities of the new wheels, and certainly, blaming "burrs in the spoke holes" is not a valid excuse, as any competent mechanic must check the hub condition before using it in a new build. Spoke holes, if there were burrs (unlikely, on a wheel you rode for a year without problems) can be deburred easily.

My recommendation: discuss these things with the owner or manager of the shop (not the mechanic who did the work, unless that is the manager), and ask him to rebuild the wheels again, properly, with new spokes and rims. If he agrees, and does it, then well and good. If not, cut your losses, and move on to a shop with a higher level of competence.

Answer 2

"Burrs on the hub" sounds bogus to me. Could be the case with a new hub, but burrs would be worn away with use.

It seems most likely that the hub was reassembled by "unskilled labor" (the new/careless guy in the shop) and he didn't notice that the hub holes are directional -- there is a countersink on one side of the hole and not the other -- or didn't understand how you put spokes in such a hub.

When the holes are directional, you put the head of the spoke on the non-countersunk side, so that the curve of the spoke mates with the smooth countersink. Placing spokes the opposite way will result in the curve of the spoke being against the sharp corner of the hole (and a broken spoke).

To check this, look at any hole where a spoke is broken. If the two sides the hole are different, the side with the smooth rounded countersunk shape should be matched with the bend in the spoke, and the head should be on the other side.

Another possibility is that machine spokes were used. These spokes have a longer distance between the head and the bend, to simplify things for lacing machines. But these are bad for hand lacing, as there is too much "lever arm" unsupported by the spoke hole, and the heads will tend to pop off. If such spokes are used one must use small spacer washers on the head side to pull the bend tightly to the curve of the spoke hole.

Or, of course, they could be lousy spokes.

(If they were breaking at the rim end this would be due to the way the rim is drilled and possible missassembly placing left-facing drilled holes with a right-facing spoke, or simply spokes that aren't strong enough to stand up to the stress of being slightly bent at the nipple.)

Answer 3

You should be able to investigate the hub yourself particular after the next spoke breaks. Think of the breaks as a series where the first breaks followed by others after the wheel has lost true. The first in each series of breaks will be at the flange if the hub has issues. Otherwise look to have the wheel rebuilt elsewhere. Why risk your safety on a job they are repeatedly doing wrong, even if it is "free".

Answer 4

If the wheel keeps on failing - for some unidentified reason - you have to review the variables: - the rim - the hub - the spokes - the construction

From your description it's probably not the rim and, like @Daniel says, 'burrs on the hub' sounds like some fake techno-jargon you're being fobbed off with.

It certainly sounds like the spokes are failing to do the job the wheel builder is expecting of them. I'm a similar size and when I had some wheels made recently the builder used tandem spokes for their extra strength. Every little helps.

That said, it sounds like, unless you've a particular reason to keep with them, finding another shop might keep you safe and sane - and a second opinion is rarely a bad thing in this sort of situation.

Answer 5

I would say you got a terrible wheel build, but you might also have some slight gradual bulging around the nipple holes which would cause the wheel to loosen up. It is still a terrible build because the builder of your wheel should have noticed that.

It would probably be best for you to buy a new wheel unless you need to keep the hub for some reason or the wheel is an odd size.

One more thing, are you really hammering the wheel? Are you riding off curbs with a skinny road wheel?

You need a much better builder.