3

I have a Giant Escape hybrid bike, which I bought as a secondhand bicycle. After I had bought it, once in every 500km, according to Strava records, I am always having a broken spoke in rear wheel. Yesterday, I got my sixth broken spoke and I have noticed the old spokes broken always, not the ones I had replaced.

I asked from a few repair persons but they just replaced the spoke without reasoning. Is there anything I can do to stop this? Because I think this is strange.

enter image description here

As you can see in this picture most of the broken spokes are on drive side. As I remember I heard sound of breaking when I tried to speed up quickly.

Most of the time the spokes break at the J Bend, not the nipple/rim. They all broke in the rear wheel, none in the front wheel. Most are on the drive side, and few are on the non-drive side.

I am more or less 85kg (187 pounds) who commutes 8km/5miles up and down (16km/10 miles daily) with, most probably, 2kg (4.4 pound/ 4lb7oz) bag. While riding I have to go on concrete roads, uneven terrain, for about 2km/2200 yards. Moreover, I used to ride more than 50km/31 miles on weekends.

Improve this question
12
  • 2
    Are spokes breaking at the rear wheel only or both front and rear? We ask such details because a common cause of spokes breaking on the rear, drive side, is damage from the chain falling off the (last) cog and getting wedged between cog and spokes.
    – gschenk
    Commented Jan 20, 2020 at 16:20
  • 3
    It may be the time you had the wheel rebuilt with new spokes. Or, depending on the price of work in your country, a new wheel could be cheaper.
    – Vladimir F Героям слава
    Commented Jan 20, 2020 at 16:37
  • 4
    Any idea how much distance is on the bike already? Spokes have a limited lifetime, and it's not unusual for them to need replacing after 50,000-100,000km. You probably should break down and get the wheel respoked, or simply buy a new wheel (which is often cheaper than respoking).
    – Daniel R Hicks
    Commented Jan 20, 2020 at 16:40
  • 2
    A common problem is drive side spokes get damaged when a chain drops of the cassette. If all the broken spokes are drive side, then inspect all of the drive side spokes (behind the cassette) for scratches and gouges (Which cause a stress raiser and fatigue).
    – mattnz
    Commented Jan 20, 2020 at 20:06
  • ...also, consider learning how to replace spokes yourself. Its not hard, just dirty.
    – Criggie ♦
    Commented Jan 20, 2020 at 21:28

5 Answers 5

Reset to default
5

Check if all spokes are properly tightened. if some spokes are too loose that can put extra stress on the rest of the spokes which can cause premature failure. If so (some of the spokes are not properly tensioned) you should true the wheel (or have it done if you don't feel comfortable doing it yourself).

Is the back wheel the original back wheel that came with the bike or has it been replaced with an aftermarket rear wheel? If so it might be of lesser quality (in which case the spokes will most likely also be of lesser quality).

How old is the bicycle/how old are the wheels? Metal gets 'tired' after a certain number of load cycles ( https://en.wikipedia.org/wiki/Fatigue_(material) ). (If the spokes break when trying to tighten them to a normal level the problem is most likely metal fatigue and you should either replace all spokes or replace the wheel (the latter is a more realistic option)). If the wheel is indeed quite old, the spokes are all properly tensioned and there is no other reason to suspect spoke failure metal fatigue might be the issue, if so (as afore mentioned) either replace all (old still remaining) spokes or replace the wheel (which is more conveneint/also cheaper in most cases). Spokes are quite cheap but rebuilding the wheel will take a considerable amount of time.

Where are the spokes failing (at what point on the spoke do they break, near the nipple, near the j-bent?) Can you add an image of the surface of the spoke at the break point? The type of surface at the failure point can give an indication of the failure mode (if it failed due to fatigue or overloading (putting too much stress on the spoke).

I quote:

Fatigue usually begins from a stress concentration at the surface. The fatigue cracks grow slowly and usually leaves a striated pattern that looks like a smooth sea shell. Then, when the crack has gone far enough, the object will break suddenly due to the stress in the small remaining area exceeding the ultimate strength. This sudden fracture will usually look different - rough or torn looking.

enter image description here

Source: http://www.learneasy.info/MDME/MEMmods/MEM30007A/properties/Properties.html

enter image description here

Source: https://www.fastenal.com/en/3289/fastener-fatigue

enter image description here

Source: https://www.sciencedirect.com/topics/engineering/tensiles

Improve this answer
4
  • 2
    To change this answer from a series of questions to an answer add what should be done if the answer to your question is "yes" If spokes are not property tightened what should be done? If the wheel is of poor quality what should be done? If the spokes are fatigued what should be done? If the spokes are failing at a specific point what should be done?
    – David D
    Commented Jan 20, 2020 at 17:14
  • 1
    @DavidD Answer has been edited. Thanks for pointing it out
    – Maarten -Monica for president
    Commented Jan 20, 2020 at 17:27
  • 2
    This answer provides lots of insight. One word of caution is to avoid confusing butted spokes with the picture for tensile break above. Butted spokes are thicker at the ends and thinner in the middle by design. So just because a spoke may be thinner in the middle (for a considerable distance) doesn't mean it's about to break.
    – ichabod
    Commented Jan 20, 2020 at 21:24
  • @Maarten-Monicaforpresident, First of all, thanks for the descriptive answer. Unfortunately, I don't know any history of the bike. But while taking above photograph I noticed some spokes aren't original. Some of them appear as painted to show as original. That's one point of suspicion. Anyway, I will check the last broken spoke. All of them broken around J bend.
    – Hareen Laks
    Commented Feb 12, 2020 at 3:39
4

Unless a spoke is damaged by external forces (e.g. chain falling off the largest cog) they usually break because of insufficient or uneven spoke tension. A spoke should always be under tension. When it’s repeatedly unloaded it can rub a teeny tiny bit against the spoke holes in the hub and the accumulated wear usually causes it to break at the bend after some time.

All the pictures of the Giant Escape I can find show entry-level wheels with 32 spokes and normal, double-walled aluminium rims. They should be sufficiently strong for light off-road use, light luggage and a not-too heavy rider (let’s say less than 100kg).

I think your bicycle mechanics are reluctant to replace all spokes because it’s much easier and cheaper to replace a single spoke only. The labour costs of rebuilding a whole wheel are often greater than getting a new, entry-level wheel.

You have a few options:

  • Check the spoke tension of the wheel (best done with a spoke tensiometer) and check for visible damage. Replace any damaged spokes and correct the tension. This is the cheapest option, but if spokes are already worn you could still suffer a break at any point in time.
  • Have the whole wheel rebuilt with new spokes and spoke nipples. Probably almost as expensive as a new wheel. If you do it yourself it’s best done with specialised equipment and quite fiddly and time consuming.
  • Get a new wheel. This is probably your only option if you are a heavier (or more “abusive”) rider. Even on new wheels it makes sense to check the spoke tension (and correct it if necessary) after a few hundred kilometres.
Improve this answer
6
  • 1
    "it can rub a teeny tiny bit against the spoke holes in the hub and the accumulated wear" is not how metal fatigue works. Also, there are certain spokes that are trash and just don't last in continued use no matter how evenly tensioned.
    – ojs
    Commented Jan 21, 2020 at 13:53
  • @ojs: Even cheap spokes should be strong enough that you don’t enter metal fatigue territory if you have an appropriate amount and spoke tension. That’s the reason why going to 2.3mm spoke diameter at the head is no magic cure and a properly built wheel (even with “standard” spokes) can last tens of Mm.
    – Michael
    Commented Jan 21, 2020 at 14:52
  • My experience is different. I have had a new wheel with no-brand that started breaking spokes from 1000km, the tension was perfect and it was fixed by professionals a few times. On the other hand, I have never broken a DT Swiss spoke even though they have been in wheels built by a total beginner (me) and one of these wheels had very uneven tension for first few thousands. It's not about price either, because those name brand spokes cost about 30 cents per piece.
    – ojs
    Commented Jan 21, 2020 at 15:31
  • Okay, maybe the spokes on the first wheel really were crap or corroded. For example I’m not sure how well Sapim’s Zinc spokes would hold up (especially in corrosive environments) despite having almost the same strength as their other spokes. It can also be a matter of how well they fit into the spoke holes of the hub. For example I’ve heard that Sapim spokes have a wider radius and should be used with washers for best performance.
    – Michael
    Commented Jan 21, 2020 at 15:48
  • They were stainless steel, and snapped just like fatigue failure described in the other answer, right at the curved part. My guess is that it was a bad batch.
    – ojs
    Commented Jan 21, 2020 at 20:02
3

First, start going to a different bike shop. The one that is putting in one new spoke at a time on that wheel each time you break one isn’t doing you any favors.

Consider having your wheel rebuilt (i.e. all new spokes) by someone who knows what they’re doing or buying a replacement wheel. If you think you’re a little heavy relative to the strength of the wheel (for example, if you have a 20-spoke wheel and you’re 260lbs) just buy a new stronger wheel. A competent bike shop mechanic can guide you here.

Improve this answer
2
  • A sronger wheel means a wheel with more spokes?
    – Hareen Laks
    Commented Feb 12, 2020 at 4:03
  • @HareenLaks more spokes will require q whole new rim, spokes, hub, and nipples. But it would be stronger. I think you have a 28 spoke rear wheel, which is not a lot for "riders like us" I run 36 spoke on most of my rear wheels where I had the choice.
    – Criggie ♦
    Commented Feb 12, 2020 at 6:35
2

I have a Giant road bicycle, a 1999 model. At about the same interval that you describe, I would break a spoke on the drive side of the rear wheel. That side is where the spokes almost always break, because the stress on that side is much higher.

After replacing several spokes, I asked the owner of my LBS why they were breaking. "Cheap spokes from Taiwan," he replied. He said that spokes from Taiwanese manufacturers from that era were prone to breaking. I weigh about 90 kg, which makes the problem worse of course.

The owner of the LBS predicted that once I had replaced all the spokes on the drive side of the rear wheel (with spokes that he sold me), then I would have much less failures. And so it has turned out to be: I broke a few more after I talked to him, but soon afterwards the breaking stopped. I haven't broken a spoke in over two years now.

Improve this answer
1
  • 1
    It seems like same issue as mine. I weigh around 85Kg.
    – Hareen Laks
    Commented Feb 12, 2020 at 3:59
1

If the failures happen to be at the bend on the non drive side it's almost certainly metal fatigue arising from insufficient tension. If the fatigue damage to the unbroken spokes hasn't gone too far it MAY be useful to increase tension in all spokes, say 1 nipple turn each. It may already be too late :(

Improve this answer
2
  • Most of the spokes are on rear wheel drive side.
    – Hareen Laks
    Commented Feb 12, 2020 at 4:04
  • This is a good and accurate answer, though its not limited to NDS side only. A wheel with low spoke tension overall will "cycle" to more extreme limits and will fatigue sooner. The bend in spokes is a weak spot because its bent during manufacture. Also if the drive side spokes have been damaged by a chain drop, loose spokes can break at this damage too.
    – Criggie ♦
    Commented Feb 12, 2020 at 6:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.