Spokes broken at cross . . .
02-07-15, 03:10 PM
#1
Senior Member
Thread Starter
Join Date: Jan 2010
Location: Wahiawa. Oahu
Posts: 1,701
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Spokes broken at cross . . .
Guy brought me a front wheel last week with a broken spoke (broken about 3-4" from the hub). Replaced it, retensioned and retrued.
This morning he's back with the rear wheel, same situation on the drive side. This time I payed more attention and I notice it is broken at the cross. Tension is about right if a little low--average about 100Kgf. Also a little uneven, but not really bad at all.
So what causes an otherwise average wheel to break a spoke at the cross? Is it just general fatigue? Wheels are maybe 9 years old and the guy is a powerful rider. I'd guesstimate his weight at 170. Thank you
This morning he's back with the rear wheel, same situation on the drive side. This time I payed more attention and I notice it is broken at the cross. Tension is about right if a little low--average about 100Kgf. Also a little uneven, but not really bad at all.
So what causes an otherwise average wheel to break a spoke at the cross? Is it just general fatigue? Wheels are maybe 9 years old and the guy is a powerful rider. I'd guesstimate his weight at 170. Thank you
Last edited by ClarkinHawaii; 02-07-15 at 03:34 PM.
02-07-15, 03:33 PM
#2
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,713
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5781 Post(s)
Liked 2,578 Times
in
1,429 Posts
Are these galvanized spokes? (check with a magnet). They appear to be (based on color), and there appears that there's some corrosion at the other crosses and nipples.
If they are not stainless steel, it might be that the crosses hold small amounts of water forming a miniscus at the cross and promoting corrosion there. Same thing where water wicks into nipples. So the rust eats into the steel causing a weakened area which eventually lets go from either metal fatigue or simply from tension.
If they, are stainless, look for black inclusions elsewhere in the spokes. These black dots or veins are signs of chloride damage, which some grades of stainless are very prone to. If you see any of the black dots, try flexing or bending the spoke there, and you'll see how brittle chlorides can make stainless.
Whether, rusted galvanized spokes, or chloride damaged stainless, consider ALL the spokes to be toast.
If they are not stainless steel, it might be that the crosses hold small amounts of water forming a miniscus at the cross and promoting corrosion there. Same thing where water wicks into nipples. So the rust eats into the steel causing a weakened area which eventually lets go from either metal fatigue or simply from tension.
If they, are stainless, look for black inclusions elsewhere in the spokes. These black dots or veins are signs of chloride damage, which some grades of stainless are very prone to. If you see any of the black dots, try flexing or bending the spoke there, and you'll see how brittle chlorides can make stainless.
Whether, rusted galvanized spokes, or chloride damaged stainless, consider ALL the spokes to be toast.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
02-07-15, 03:40 PM
#4
Banned
Climatically, Hawaii, Surrounded By an Ocean, Salt* is in the air , And being warm more Moisture can be carried in suspension as Mist.
*NaCl (Sodium Chloride)
*NaCl (Sodium Chloride)
Last edited by fietsbob; 02-07-15 at 04:05 PM.
02-07-15, 03:55 PM
#5
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,713
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5781 Post(s)
Liked 2,578 Times
in
1,429 Posts
Did you confirm with a magnet? Note that some grades of stainless are slightly magnetic.
I'm pushing you on this based on the color, (most stainless spokes are yellowish, not neutral gray) and what appears to be rust on some of the other spokes.
Corrosion or chloride damage in stainless steel is usually black, not reddish, and wouldn't normally extend out from the primary source as these appear to.
I'm pushing you on this based on the color, (most stainless spokes are yellowish, not neutral gray) and what appears to be rust on some of the other spokes.
Corrosion or chloride damage in stainless steel is usually black, not reddish, and wouldn't normally extend out from the primary source as these appear to.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
02-07-15, 04:07 PM
#6
Senior Member
Thread Starter
Join Date: Jan 2010
Location: Wahiawa. Oahu
Posts: 1,701
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Yes they are just slightly magnetic but not clangin' death-grip magnetic like carbon steel spokes. All of the crosses appear to show rub-marks/abrasions at the crosses. I'm primarily interested in what to recommend to the guy. He commutes to work on his bike and also carries toddlers in child seat, so I want him to be uber-safe. I could only find one isolated black spot other than the marks at the crosses.
More pics:
More pics:
02-07-15, 04:20 PM
#7
Senior Member
Thread Starter
Join Date: Jan 2010
Location: Wahiawa. Oahu
Posts: 1,701
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
the rust-colored stains appear to just be dirt, as they wipe right off. Our dirt here is red.
02-07-15, 04:25 PM
#8
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,713
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5781 Post(s)
Liked 2,578 Times
in
1,429 Posts
The gouges in the earlier photos are from the chain which must have over shifted beyond the top sprocket at one time or another. If the spokes have well worn notches at the crosses, that speaks to age (in miles) since this notching comes from the slight movement there as the wheel flexes.
The best way to test or chloride damage is to remove the other spoke and flex it near the dark spot. If the salt got to the steel it's snap like raw spaghetti.
Barring other damage, it's a crossroads. You might replace the single spoke (first broken one so far) and buy the owner some time. Or if there is chloride damage, or even if not, the spokes may be nearing the end of their service life and a complete rebuild might be called for. If going that route check rim for wear since there's no sense building with a rim that is also nearing the end.
I can't see fee or smell the wheel, so can't make a judgement call whether to fix or rebuild, but if you and the customer opt for replacing the one spoke, make sure he understands that the next failure can happen soon, or may not happen for another year or two. IME it takes two broken spokes to establish a time line. 1 broken spoke is a fluke, 2 sets the schedule with each future break coming sooner than the one before.
The best way to test or chloride damage is to remove the other spoke and flex it near the dark spot. If the salt got to the steel it's snap like raw spaghetti.
Barring other damage, it's a crossroads. You might replace the single spoke (first broken one so far) and buy the owner some time. Or if there is chloride damage, or even if not, the spokes may be nearing the end of their service life and a complete rebuild might be called for. If going that route check rim for wear since there's no sense building with a rim that is also nearing the end.
I can't see fee or smell the wheel, so can't make a judgement call whether to fix or rebuild, but if you and the customer opt for replacing the one spoke, make sure he understands that the next failure can happen soon, or may not happen for another year or two. IME it takes two broken spokes to establish a time line. 1 broken spoke is a fluke, 2 sets the schedule with each future break coming sooner than the one before.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
02-07-15, 04:31 PM
#9
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,081
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4204 Post(s)
Liked 3,862 Times
in
2,310 Posts
Usually a single or two broken spoke(s) (at the same time) doesn't create a dangerous situation. In fact the dent a pot hole hit can produce can be FAR worse.
So what I would do (and do in similar situations with my customers) Is to explain the possibilities as you know them, suggest what you think is the best option and let the customer decide.
BTW to tangent a bit. This situation brings to my mind what are the responsibilities that we have as professional mechanics. (And any one being paid is a pro, regardless of whether they have a DBA/chapter S/partnership/or other business which is recognized by the state or fed tax people). The OP notes that his customer's kid is sometimes being ridden on the bike. I REALLY hope the OP has insurance for that kid's future needs if the worst should happen. Andy.
So what I would do (and do in similar situations with my customers) Is to explain the possibilities as you know them, suggest what you think is the best option and let the customer decide.
BTW to tangent a bit. This situation brings to my mind what are the responsibilities that we have as professional mechanics. (And any one being paid is a pro, regardless of whether they have a DBA/chapter S/partnership/or other business which is recognized by the state or fed tax people). The OP notes that his customer's kid is sometimes being ridden on the bike. I REALLY hope the OP has insurance for that kid's future needs if the worst should happen. Andy.
02-07-15, 04:46 PM
#10
Senior Member
Thread Starter
Join Date: Jan 2010
Location: Wahiawa. Oahu
Posts: 1,701
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
The gouges in the earlier photos are from the chain which must have over shifted beyond the top sprocket at one time or another. If the spokes have well worn notches at the crosses, that speaks to age (in miles) since this notching comes from the slight movement there as the wheel flexes.
The best way to test or chloride damage is to remove the other spoke and flex it near the dark spot. If the salt got to the steel it's snap like raw spaghetti.
Barring other damage, it's a crossroads. You might replace the single spoke (first broken one so far) and buy the owner some time. Or if there is chloride damage, or even if not, the spokes may be nearing the end of their service life and a complete rebuild might be called for. If going that route check rim for wear since there's no sense building with a rim that is also nearing the end.
I can't see fee or smell the wheel, so can't make a judgement call whether to fix or rebuild, but if you and the customer opt for replacing the one spoke, make sure he understands that the next failure can happen soon, or may not happen for another year or two. IME it takes two broken spokes to establish a time line. 1 broken spoke is a fluke, 2 sets the schedule with each future break coming sooner than the one before.
The best way to test or chloride damage is to remove the other spoke and flex it near the dark spot. If the salt got to the steel it's snap like raw spaghetti.
Barring other damage, it's a crossroads. You might replace the single spoke (first broken one so far) and buy the owner some time. Or if there is chloride damage, or even if not, the spokes may be nearing the end of their service life and a complete rebuild might be called for. If going that route check rim for wear since there's no sense building with a rim that is also nearing the end.
I can't see fee or smell the wheel, so can't make a judgement call whether to fix or rebuild, but if you and the customer opt for replacing the one spoke, make sure he understands that the next failure can happen soon, or may not happen for another year or two. IME it takes two broken spokes to establish a time line. 1 broken spoke is a fluke, 2 sets the schedule with each future break coming sooner than the one before.
02-07-15, 10:39 PM
#11
Senior Member
Thread Starter
Join Date: Jan 2010
Location: Wahiawa. Oahu
Posts: 1,701
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Usually a single or two broken spoke(s) (at the same time) doesn't create a dangerous situation. In fact the dent a pot hole hit can produce can be FAR worse.
So what I would do (and do in similar situations with my customers) Is to explain the possibilities as you know them, suggest what you think is the best option and let the customer decide.
BTW to tangent a bit. This situation brings to my mind what are the responsibilities that we have as professional mechanics. (And any one being paid is a pro, regardless of whether they have a DBA/chapter S/partnership/or other business which is recognized by the state or fed tax people). The OP notes that his customer's kid is sometimes being ridden on the bike. I REALLY hope the OP has insurance for that kid's future needs if the worst should happen. Andy.
So what I would do (and do in similar situations with my customers) Is to explain the possibilities as you know them, suggest what you think is the best option and let the customer decide.
BTW to tangent a bit. This situation brings to my mind what are the responsibilities that we have as professional mechanics. (And any one being paid is a pro, regardless of whether they have a DBA/chapter S/partnership/or other business which is recognized by the state or fed tax people). The OP notes that his customer's kid is sometimes being ridden on the bike. I REALLY hope the OP has insurance for that kid's future needs if the worst should happen. Andy.
Thread
Thread Starter
Forum
Replies
Last Post
ClarkinHawaii
Bicycle Mechanics
1
05-06-15 11:47 AM
ClarkinHawaii
Bicycle Mechanics
11
02-06-15 02:36 PM
