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Old 06-13-10, 04:33 PM   #1
pstock
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what do these paint crackles mean?

off a colnago fork.
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Old 06-13-10, 05:19 PM   #2
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It looks like it could be the result of a crash. Check your steerer tube carefully to make sure it is not bent. Check to make sure it is straight at the junction where it joins the fork crown.

-j
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Old 06-13-10, 05:43 PM   #3
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Looks like a bent fork.
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Old 06-13-10, 07:59 PM   #4
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If you know that the forks have never been crashed and they are straight then what you have is an example of how a brittle paint job is less flexible than the underlaying body and how it can crack when flexed in compression or tension. Assuming that this is the front of the fork legs then what happened is that the constant flexing forward due to springing when hitting bumps and potholes flexed the legs more than the paint could withstand and it failed from compression of the paint film and a failure of the bond between the metal and paint film.
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Old 06-13-10, 09:33 PM   #5
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It means the metal underneath the paint is cracked. bk
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Old 06-14-10, 10:23 AM   #6
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If it was mine,It means I need to remove the paint and look at it more closely.Magnaflux it if you don't actually see any cracks.
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Old 06-14-10, 10:59 AM   #7
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That's not a paint flaw. That's a bike that was bent.
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Old 06-14-10, 11:05 AM   #8
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I'm assuming that the gold coloured cloverleaf is on the front side of the fork. Not many cases of graphics of that sort on the rear side. Generally a collision would bend the fork leg BACK and the cracks in the paint or in the metal would occur on the front. So a paint bond failure due to the metal stretching from road roughness and vibration is far more likely than the tales of doom and gloom given so far.

It would certainly be worth removing the paint and checking things over though. The paint is going to eventually chip away in any event.
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Old 06-14-10, 11:14 AM   #9
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If it wasn't crashed then it was not properly prepared at the factory prior to painting.
Paint is flexible. Look at all the other bikes that don't have that problem. I'm sure their forks flex also.
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Old 06-14-10, 11:27 AM   #10
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Not all paints are all that flexible. Also a lot depends on the bond to the substrate and the adhesion with any primers used. Back in the late 80's and well into the 90's when the shift was made to low volitility paints a lot of things came out on the market with paint bonding issues. There were a sizable number of cars with this issue. I know because I had one of them and by the time I junked it the darn thing looked like it was a snake shedding its skin. I suspect that this Colnago frame is another example of such a thing. The OP also has a companion thread about this frame running in parallel with this question about the forks. And when you see the chips out of the paint on the frame and how it looks like you could slip a fingernail under the edges and lift off another big chip I think you'll all agree that this is more a paint film failure than due to fork damage.

In any event it's always good to check for signs of impact. In the case of a fork ensuring that the upper portion of the legs is parallel to the steerer tube is always a good sign that all is well. But if bent back by more than a degree or two that trouble is locked away.
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Old 06-14-10, 12:15 PM   #11
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The crack is right through the metal, that's grease seeping through. Do not ride that fork.
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Old 06-14-10, 12:17 PM   #12
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I'd be as concerned about the corrosion that's started under the paint as I would be about the cracks themselves. In any case, get the paint stripped off (preferably chemically) and have the forks magnafluxed. IF they pass the 'fluxing, consider phosphoric acid to halt the rusting before repainting.
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Old 06-14-10, 12:27 PM   #13
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They mean it's time to get a new bike.

Enjoy
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Old 06-14-10, 12:33 PM   #14
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People deal with a little rust on their steel bikes all the time. I can't believe the sudden onset of woe and doom that I'm seeing in this thread. At worst there's a little bit of rust going on behind the cracks in the paint. If the metal isn't pitted badly below the paint then there's no big deal about stripping the paint off and re-finishing the forks and using them for many fun filled years to come.
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Old 06-14-10, 12:50 PM   #15
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Quote:
Originally Posted by BCRider View Post
People deal with a little rust on their steel bikes all the time. I can't believe the sudden onset of woe and doom that I'm seeing in this thread. At worst there's a little bit of rust going on behind the cracks in the paint. If the metal isn't pitted badly below the paint then there's no big deal about stripping the paint off and re-finishing the forks and using them for many fun filled years to come.
Anyone that has spent time working on bikes would recognize those cracks as the result of a front end collision.
Yea, you could ride a bent up steel frame for years but why would you?

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Old 06-14-10, 12:54 PM   #16
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So why are the cracks on the REAR side of the fork? The Colnago graphic indicates the front side of the fork and it doesn't have any cracking. Having said this I've also already posted that the forks should be checked.

Check out the OP's companion thread about the entire frame. There's lots of evidence from the nature of the chipping on the frame that the issue here is simply a paint bonding failure coupled with some neglectful handling.
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Old 06-14-10, 01:21 PM   #17
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Quote:
Originally Posted by BCRider View Post
Not all paints are all that flexible. Also a lot depends on the bond to the substrate and the adhesion with any primers used. Back in the late 80's and well into the 90's when the shift was made to low volitility paints a lot of things came out on the market with paint bonding issues. There were a sizable number of cars with this issue. I know because I had one of them and by the time I junked it the darn thing looked like it was a snake shedding its skin. I suspect that this Colnago frame is another example of such a thing. The OP also has a companion thread about this frame running in parallel with this question about the forks. And when you see the chips out of the paint on the frame and how it looks like you could slip a fingernail under the edges and lift off another big chip I think you'll all agree that this is more a paint film failure than due to fork damage.

In any event it's always good to check for signs of impact. In the case of a fork ensuring that the upper portion of the legs is parallel to the steerer tube is always a good sign that all is well. But if bent back by more than a degree or two that trouble is locked away.
If I recall correctly, 80's and early 90's Colnagos were known to have paint issues.
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Old 06-14-10, 01:24 PM   #18
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Rust can cause paint cracks that are perfectly straight? I don't think so.
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Old 06-14-10, 01:46 PM   #19
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So why are the cracks on the REAR side of the fork?
I've seen rear cracks caused by forward bending before - from repeatedly coming down hard from wheelies or going down off a curb.
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Old 06-14-10, 01:52 PM   #20
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Not rust but the stretching of the rear side occurs on the rear of the fork legs when going over rough roads certainly does produce this sort of paint bond failure if the paint is not 100% up to the job. Rust blooms in the cracks would come afterwards once the paint opens up the steel to the elements.

None of this is suggesting that there is not some possible collision damage to the fork. That would require further checking of the fork. But the sort of paint failure I'm seeing is entirely possible without the aid of collision damage. And again the fact that the paint damage is on the REAR of the fork leg and the sort of paint failure on the frame would suggest that this is likely the case.

Thankyou Vredstein. Posting this question on the C&V forum would very likely turn up an answer if there is such a history.
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Old 06-14-10, 01:55 PM   #21
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I've seen rear cracks caused by forward bending before - from repeatedly coming down hard from wheelies or going down off a curb.
But you'd have to admit that it would be unlikely to find something like a Colnago road frame that saw that sort of history. Besides if the paint itself is just suffering from issues the steel forks would be just fine in behind the damaged paint.
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Old 06-14-10, 01:58 PM   #22
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If it was mine,It means I need to remove the paint and look at it more closely.Magnaflux it if you don't actually see any cracks.
I got to agree with this...if it was mine I would do this before I decide what to do with the rest of the frame. I didn't see any real damage on the frame other than (what I THINK are) paint issues, but it was also hard to tell from some of the shots maybe if you posted less close ups and more wide veiws.
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Old 06-15-10, 01:16 PM   #23
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more pictures

sorry, I should have included more and clearer pictures.

for the record, the crackles are on the front of the forks.

and laying a straight edge (or as straight an edge as I have that length) along the front of each leg, doesn't not look encouraging.
Attached Images
File Type: jpg fork RHside 2..jpg (72.4 KB, 39 views)
File Type: jpg fork RHside1..jpg (74.4 KB, 32 views)
File Type: jpg fork back..jpg (74.9 KB, 35 views)
File Type: jpg fork LHside1..jpg (75.4 KB, 36 views)
File Type: jpg fork RHside 3..jpg (74.3 KB, 36 views)
File Type: jpg ruled RH..jpg (85.5 KB, 54 views)
File Type: jpg ruled LH..jpg (84.4 KB, 42 views)
File Type: jpg front of fork..jpg (75.9 KB, 44 views)
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Old 06-15-10, 02:11 PM   #24
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Note that the kink that the ruler is sitting on is below the crackles. And looking at the side pictures it's quite obvious that the fork leg starts out as a constant width upper portion then transitions to a tapered lower portion. All your latest pictures show the fork to be just fine. I'm still sticking to this being a paint bond failure issue. Note how the one part is chipped out cleanly almost like a wall tile that came loose and fell out. Get into that spot with a small knife blade and I'll bet you can lift away a lot more paint that is only semi held on to the base metal. I'm not seeing anything to support a collision being the cause. Even the steer tube is nicely canted forward as it should be in the one picture.
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Old 06-15-10, 06:52 PM   #25
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The only way to know is to sand or peel the paint off to the bare metal in that area.
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