Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

What Causes This Type Of Damage?

Search
Notices
Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

What Causes This Type Of Damage?

Thread Tools
 
Search this Thread
 
Old 03-02-23, 05:38 PM
  #26  
bulgie 
blahblahblah chrome moly
 
bulgie's Avatar
 
Join Date: Apr 2009
Location: Seattle
Posts: 1,994
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1181 Post(s)
Liked 2,576 Times in 1,076 Posts
Originally Posted by thumpism
I have French replacement chrome-plated CroMo fork. I'll dig it out and take a look. Offered it to a Peugeot guy years ago but he passed.
Those forks sold as replacements often had a ridiculous number of threads, trying to fit all frame sizes with one fork. Those sellers should be hung up by their thumbs!

True, they make a perfectly fine replacement for a small enough frame where the bottom of the threads happens to end up in the right place. But on the biggest frame they fit, the quill is definitely going to be tightening on the threaded part. (And the bigger rider on that bigger frame is probably heavier, stresses bike parts more.).

Imagine you're JRA when the whole stem/bars are suddenly no longer attached by anything but the brake cables. It breaks free with the top of the steerer, headset screwed race and top nut still attached. It'll probably happen when you're hitting the brakes hard on a downhill, so your weight is shifted forward, and there ain't no recovering from that. you're goin' down. If it snaps from hitting a big pot hole then at least you have some chance of riding it to a stop. Luckily the brakes still work, but the bike won't steer great with no upper headset anymore, broken end of the steerer rubbing on the inside of the head tube and flopping around <shiver>.

George Hincapie crashed when his steerer broke near the top, and he was a very experienced pro at the time. Most amateurs will be toast.
"OK we get it Mark, it's bad — enough already!" OK, I will drop it now!

Mark B
bulgie is online now  
Likes For bulgie:
Old 03-02-23, 05:44 PM
  #27  
Lattz
Senior Member
 
Join Date: Aug 2017
Location: Germany
Posts: 1,090

Bikes: 80s Alan Super Record, 79' Somec Special, 90s Rossin(?) Columbus Ego Triathlon, previously: Bianchi SBX Reparto Corse (stolen) and so on...

Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 391 Post(s)
Liked 813 Times in 602 Posts
Too bad you are in the states, I could give you a strong(er) period correct Gitane fork (although in peacock blue) from a tandem with intact filing where only the steerer is not like a spaghetti. Must have been hit by a CAT mining machine.
Lattz is offline  
Old 03-02-23, 06:02 PM
  #28  
BFisher
Senior Member
 
Join Date: Aug 2013
Posts: 2,321
Mentioned: 35 Post(s)
Tagged: 0 Thread(s)
Quoted: 767 Post(s)
Liked 1,898 Times in 889 Posts
What Causes This Type Of Damage?

The immortal words of the BF resident Gitane expert, one Wolfram Verktyg, instantly came to mind as I saw the graphic details - Ham-fisted Hammersmith.
BFisher is offline  
Old 03-02-23, 06:03 PM
  #29  
repechage
Senior Member
 
Join Date: Jun 2006
Posts: 20,305
Mentioned: 130 Post(s)
Tagged: 0 Thread(s)
Quoted: 3464 Post(s)
Liked 2,831 Times in 1,997 Posts
Originally Posted by 79pmooney
Maybe. But that expander/wedge should be below those threads, not completely above where they start. That silly minimum insertion line is there for that reason. Also, the bottom of the stem being there means it is too high, so a larger than intended maximum bending force (that would push back on the stem bottom when you press down on the bars hitting say a pothole). And that greater than intended bending force is resisted by a shorter lever. The force at the bottom of the stem resisting bending is in proportion to the inverse of the lever length. Say this stem was only inserted 2/3s of the way to to the min insertion line. Well, that's 1 1/2 X the bigger than designed for bending force applied at the weakest part of the steerer.

If that crack is not at the back of the steerer (your picture doesn't give any clues), I'll put on my dunce cap and go sit in the corner.
There were a bunch of decades before the CPSC minimum insertion line.
the extra threads below what the headset could use is not helping, but might well have made one fork fit multiple frame sizes.

way back it was a mechanic's judgement to prevent this or a stem failure. 55mm was the amount I typically made sure was min insertion.

on this fork 55 mm would just be beyond the threads.

assigned risk
repechage is offline  
Old 03-03-23, 06:32 AM
  #30  
Drillium Dude 
Banned.
 
Drillium Dude's Avatar
 
Join Date: Jul 2009
Location: PAZ
Posts: 12,294
Mentioned: 255 Post(s)
Tagged: 0 Thread(s)
Quoted: 2588 Post(s)
Liked 4,824 Times in 1,709 Posts
Originally Posted by bulgie

Those forks sold as replacements often had a ridiculous number of threads, trying to fit all frame sizes with one fork. Those sellers should be hung up by their thumbs!

True, they make a perfectly fine replacement for a small enough frame where the bottom of the threads happens to end up in the right place. But on the biggest frame they fit, the quill is definitely going to be tightening on the threaded part. (And the bigger rider on that bigger frame is probably heavier, stresses bike parts more.).

Imagine you're JRA when the whole stem/bars are suddenly no longer attached by anything but the brake cables. It breaks free with the top of the steerer, headset screwed race and top nut still attached. It'll probably happen when you're hitting the brakes hard on a downhill, so your weight is shifted forward, and there ain't no recovering from that. you're goin' down. If it snaps from hitting a big pot hole then at least you have some chance of riding it to a stop. Luckily the brakes still work, but the bike won't steer great with no upper headset anymore, broken end of the steerer rubbing on the inside of the head tube and flopping around <shiver>.

George Hincapie crashed when his steerer broke near the top, and he was a very experienced pro at the time. Most amateurs will be toast.
"OK we get it Mark, it's bad — enough already!" OK, I will drop it now!

Mark B
That's not beating a dead horse, it's a public service announcement. You've brought up some good points for people - especially Bigfoot's descendants - who may be running an at-risk fork.

Thankfully, I've had the opportunity to put eyeballs on the fork steerer tubes of every bike I own and operate. They all look good, so I've peace of mind in that regard. Overcompensating, yee-hawin' man-boys in lifted trucks, on the other hand, will likely be the death of me if I stay in AZ much longer!

Seriously, I hate those guys.

DD
Drillium Dude is offline  
Likes For Drillium Dude:
Old 03-03-23, 03:56 PM
  #31  
thumpism 
Bikes are okay, I guess.
 
thumpism's Avatar
 
Join Date: Jan 2015
Location: Richmond, Virginia
Posts: 6,938

Bikes: Waterford Paramount Touring, Giant CFM-2, Raleigh Sports 3-speeds in M23 & L23, Schwinn Cimarron oddball build, Marin Palisades Trail dropbar conversion, Nishiki Cresta GT

Mentioned: 69 Post(s)
Tagged: 0 Thread(s)
Quoted: 2647 Post(s)
Liked 2,446 Times in 1,557 Posts
Originally Posted by bulgie
Those forks sold as replacements often had a ridiculous number of threads, trying to fit all frame sizes with one fork. Those sellers should be hung up by their thumbs!
I was a seller then, or a rep for one, and this was the sole French fork we had, Tange with about 1/3 of the steerer threaded. Cheap generic replacements were much worse in this respect, but with French you don't have many choices.


thumpism is offline  
Likes For thumpism:
Old 03-03-23, 04:03 PM
  #32  
bulgie 
blahblahblah chrome moly
 
bulgie's Avatar
 
Join Date: Apr 2009
Location: Seattle
Posts: 1,994
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1181 Post(s)
Liked 2,576 Times in 1,076 Posts
Originally Posted by thumpism
I was a seller then, or a rep for one, and this was the sole French fork we had, Tange with about 1/3 of the steerer threaded.
Those are very high quality forks, would be awesome for whatever frame size results in all but about 20 mm of threads cut off!

At the max size, with all those threads intact, well let's just say you don't need to worry about your Death Stem, the steerer will kill you before the stem can.

OK I'm deliberately over-stating the likelihood of it breaking. Not all do, but the stakes are very high when one does.
bulgie is online now  
Old 03-03-23, 06:42 PM
  #33  
sbarner 
Paramount Fan
 
sbarner's Avatar
 
Join Date: Dec 2006
Location: Vermont
Posts: 293

Bikes: Paramounts, Raleigh Pros, Colnago, DeRosa, Gios, Masis, Pinarello, R. Sachs, Look, D. Moulton, Witcomb, Motobecane, Bianchis, Fat City, Frejus, Follis, Waterford, Litespeed, d'Autremont, others, mostly '70s-'80s

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 123 Post(s)
Liked 240 Times in 133 Posts
As others have pointed out, the split is from the stem being installed with too little insertion. French steerers are thinner than BSC or Italian by 0.1 mm which doesn't sound like much, but it's already a thin, threaded part. Most of the French forks I have seen only have the flat near the top, but they seemed to have gotten carried away at the Gitane factory that day. Still, it would not have been a problem if the stem had been correctly installed. Practically speaking, this is not a highly stressed area under normal use, as the stem provides significant reinforcement. I would not do this for a customer, but if it were mine I would insert a French stem, tap the bulge out with a hammer, put it together with the stem inserted properly, and ride it without any fear. Even in the unlikely event that a crack would propagate around the thread, which I believe is highly unlikely, a failure would not cause the loss of control one would get should the steerer separate below the stem. Replacing a steerer takes a lot of heat, or a mill and some expensive time. It is not a trivial task.
sbarner is offline  
Old 03-03-23, 06:57 PM
  #34  
79pmooney
Senior Member
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 12,906

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 129 Post(s)
Tagged: 0 Thread(s)
Quoted: 4806 Post(s)
Liked 3,932 Times in 2,557 Posts
Originally Posted by bulgie
Those are very high quality forks, would be awesome for whatever frame size results in all but about 20 mm of threads cut off!

At the max size, with all those threads intact, well let's just say you don't need to worry about your Death Stem, the steerer will kill you before the stem can.

OK I'm deliberately over-stating the likelihood of it breaking. Not all do, but the stakes are very high when one does.
A steerer crying for one of my stems, ridden as I used to ride them - slammed with a dent in the throat. Puts the nut so far down the bending force is very low and little torque on the bolt is needed. I raced in the '70s. It wasn't 'till the mid '90s I realized how much I could benefit from stems far longer than stock. Still have a few 130s with the scars from the strangler.
79pmooney is offline  
Old 03-04-23, 09:32 PM
  #35  
cudak888 
www.theheadbadge.com
 
cudak888's Avatar
 
Join Date: Sep 2005
Location: Southern Florida
Posts: 28,514

Bikes: https://www.theheadbadge.com

Mentioned: 124 Post(s)
Tagged: 0 Thread(s)
Quoted: 2422 Post(s)
Liked 4,396 Times in 2,093 Posts
Originally Posted by bulgie
Those forks sold as replacements often had a ridiculous number of threads, trying to fit all frame sizes with one fork. Those sellers should be hung up by their thumbs!

True, they make a perfectly fine replacement for a small enough frame where the bottom of the threads happens to end up in the right place. But on the biggest frame they fit, the quill is definitely going to be tightening on the threaded part. (And the bigger rider on that bigger frame is probably heavier, stresses bike parts more.).

Imagine you're JRA when the whole stem/bars are suddenly no longer attached by anything but the brake cables. It breaks free with the top of the steerer, headset screwed race and top nut still attached. It'll probably happen when you're hitting the brakes hard on a downhill, so your weight is shifted forward, and there ain't no recovering from that. you're goin' down. If it snaps from hitting a big pot hole then at least you have some chance of riding it to a stop. Luckily the brakes still work, but the bike won't steer great with no upper headset anymore, broken end of the steerer rubbing on the inside of the head tube and flopping around <shiver>.

George Hincapie crashed when his steerer broke near the top, and he was a very experienced pro at the time. Most amateurs will be toast.
"OK we get it Mark, it's bad — enough already!" OK, I will drop it now!

Mark B
Mark, I wish this could be shouted at every aftermarket bike parts importer on this earth.




Those overthreaded "replacement" forks are worthy of being on the top five list for irresponsible parts sold on the bike aftermarket today.

At this point, if I have to replace a fork with a long enough steerer tube, I'll just get the threadless equivalent, slice it to length, and cut the appropriate amount of threads into it.

-Kurt
__________________












cudak888 is offline  
Likes For cudak888:
Old 03-04-23, 09:37 PM
  #36  
bulgie 
blahblahblah chrome moly
 
bulgie's Avatar
 
Join Date: Apr 2009
Location: Seattle
Posts: 1,994
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1181 Post(s)
Liked 2,576 Times in 1,076 Posts
Originally Posted by cudak888
Mark, I wish this could be shouted at every aftermarket bike parts importer on this earth.

Those overthreaded "replacement" forks are worthy of being on the top five list for irresponsible parts sold on the bike aftermarket today.

At this point, if I have to replace a fork with a long enough steerer tube, I'll just get the threadless equivalent, slice it to length, and cut the appropriate amount of threads into it.

-Kurt
Classic! I saved that to my Hall of Shame folder of broken bikes'n'parts, it's a keeper.
bulgie is online now  
Likes For bulgie:
Old 03-04-23, 09:45 PM
  #37  
cudak888 
www.theheadbadge.com
 
cudak888's Avatar
 
Join Date: Sep 2005
Location: Southern Florida
Posts: 28,514

Bikes: https://www.theheadbadge.com

Mentioned: 124 Post(s)
Tagged: 0 Thread(s)
Quoted: 2422 Post(s)
Liked 4,396 Times in 2,093 Posts
Originally Posted by bulgie
Classic! I saved that to my Hall of Shame folder of broken bikes'n'parts, it's a keeper.
I believe I sliced off the damaged bit and abused a tap straight into the chrome to make a shorter, but still usable fork out of it. Wasn't a total loss, just a dose of reality about something that, at the time, I hadn't thought about before it happened. ("That, kids, is the value of experience. And mistakes.")

-Kurt
__________________












cudak888 is offline  
Old 03-05-23, 04:30 PM
  #38  
Murray Missile 
Senior Member
 
Murray Missile's Avatar
 
Join Date: Jun 2013
Location: 700 Ft. above sea level.
Posts: 3,251

Bikes: More than there were awhile ago.

Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 637 Post(s)
Liked 1,288 Times in 610 Posts
This had me concerned as I'm replacing a fork with one very similar to this with about as much threading. Prior to reading this thread it's not something I had given any thought to as the steerer is not slotted and I was under the misguided thinking that positioning the wedge in the slotted portion was the only issue. I'll be trimming some off the OAL but not that much. Then I remembered the threadless stem adapter I was using goes half way down the steerer tube where I have it set so even with the excessive threading the wedge will be well below the threads. It's one of those extra long ones that was on another bike I took in trade and they were using it to raise the handlebars.

Originally Posted by thumpism


__________________
".....distasteful and easily triggered."
Murray Missile is offline  
Old 03-05-23, 04:54 PM
  #39  
bulgie 
blahblahblah chrome moly
 
bulgie's Avatar
 
Join Date: Apr 2009
Location: Seattle
Posts: 1,994
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1181 Post(s)
Liked 2,576 Times in 1,076 Posts
Originally Posted by Murray Missile
This had me concerned as I'm replacing a fork with one very similar to this with about as much threading. Prior to reading this thread it's not something I had given any thought to as the steerer is not slotted and I was under the misguided thinking that positioning the wedge in the slotted portion was the only issue. I'll be trimming some off the OAL but not that much. Then I remembered the threadless stem adapter I was using goes half way down the steerer tube where I have it set so even with the excessive threading the wedge will be well below the threads. It's one of those extra long ones that was on another bike I took in trade and they were using it to raise the handlebars.
Yes that's a good solution. A bit of extra weight but better than a cracked steerer.
bulgie is online now  
Old 03-05-23, 06:43 PM
  #40  
Murray Missile 
Senior Member
 
Murray Missile's Avatar
 
Join Date: Jun 2013
Location: 700 Ft. above sea level.
Posts: 3,251

Bikes: More than there were awhile ago.

Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 637 Post(s)
Liked 1,288 Times in 610 Posts
Originally Posted by bulgie
Yes that's a good solution. A bit of extra weight but better than a cracked steerer.
If weight was a concern then I'd have some skinny guy ride it for me.
__________________
".....distasteful and easily triggered."
Murray Missile is offline  
Old 03-05-23, 07:39 PM
  #41  
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Posts: 24,790

Bikes: Several, mostly not name brands.

Mentioned: 153 Post(s)
Tagged: 0 Thread(s)
Quoted: 3590 Post(s)
Liked 3,401 Times in 1,935 Posts
Originally Posted by cudak888
Mark, I wish this could be shouted at every aftermarket bike parts importer on this earth.




Those overthreaded "replacement" forks are worthy of being on the top five list for irresponsible parts sold on the bike aftermarket today.
If they're going to cut that much thread, do us all a favor and forgo the keyway/flat for the anti-rotation washer. It's not strictly necessary if you use two wrenches when adjusting the headset, and would eliminate the weak spot where these splits occur.
JohnDThompson is offline  
Likes For JohnDThompson:
Old 03-05-23, 09:50 PM
  #42  
cudak888 
www.theheadbadge.com
 
cudak888's Avatar
 
Join Date: Sep 2005
Location: Southern Florida
Posts: 28,514

Bikes: https://www.theheadbadge.com

Mentioned: 124 Post(s)
Tagged: 0 Thread(s)
Quoted: 2422 Post(s)
Liked 4,396 Times in 2,093 Posts
Originally Posted by JohnDThompson
If they're going to cut that much thread, do us all a favor and forgo the keyway/flat for the anti-rotation washer. It's not strictly necessary if you use two wrenches when adjusting the headset, and would eliminate the weak spot where these splits occur.
Provided the washer is neither keyed or expecting French-style flatted threads, both of which will split anyway.

Not so sure I trust a wedge on threads either.

-Kurt
__________________












cudak888 is offline  
Old 03-05-23, 10:02 PM
  #43  
Homebrew01
Super Moderator
 
Homebrew01's Avatar
 
Join Date: Jul 2004
Location: Ffld Cnty Connecticut
Posts: 21,843

Bikes: Old Steelies I made, Old Cannondales

Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 1173 Post(s)
Liked 927 Times in 612 Posts
Originally Posted by Velo Mule
What?? Wait!! What is that? I'm agreeing with @panzerwagen that this split is from the stem expander, however, it looks like there are no threads in just that area but are around the rest of the steerer tube. That area also looks to be painted rather than bare metal.

Was this section of the steerer tube indented, which would be why it didn't get threaded and then got painted? Then being indented, cracked when the stem expander was tightened?

Can we get a few more pictures from different angles. This sure is odd.
Maybe the split stuck out, rubbing inside the head tube. So sombody filed down the bulge and sprayed on a bit of paint.
__________________
Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike.

FYI: https://www.bikeforums.net/forum-sugg...ad-please.html
Homebrew01 is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.