Johan Bornman Posted February 17, 2010 Share This bike belongs to a friend who lives in the sticks. Last week he sent the bike to me to have a look at the head tube. I won't reveal what brand it is, but here's a photo of the cracked head tube. The red marks indicate the start and end of the crack. The construction of the head tube seems to be a plain tube with two headset cup flanges welded onto each side and then machined to smooth out the weld. The crack started at the bottom of the flange and ends with the out-of-focus bit. On closer inspection I discovered that the headset cup itself is also cracked. This crack isn't all that clear but look for the dark line in the 25-past position. It corresponds with the crack in the frame. Which crack started first? Which caused what? Link to comment Share on other sites More sharing options...
Jono Waddell Posted February 17, 2010 Share You didn't do to well in trying to hide the brand there. Link to comment Share on other sites More sharing options...
Noneking Posted February 17, 2010 Share Have I got the wrong topic? Link to comment Share on other sites More sharing options...
Dirt*girl™ Posted February 17, 2010 Share canzp...hee hee, I was thinking the same thing. I thought he was talking about a hubber...oh nevermind. Link to comment Share on other sites More sharing options...
CAAD4 Posted February 17, 2010 Share No man. You've just opened the door for Conti. I'm off. Link to comment Share on other sites More sharing options...
Dirtbreath Posted February 17, 2010 Share Maybe both were created simultaneously when pressing the cup in? Link to comment Share on other sites More sharing options...
Cassie Posted February 17, 2010 Share OK, so how much abuse did the bike get to result in a crack like that? Must have been some serias downhill stuff? on a rigid fork? Link to comment Share on other sites More sharing options...
Tumbleweed Posted February 17, 2010 Share You didn't do to well in trying to hide the brand there. ok, i give up?what brand is it? Link to comment Share on other sites More sharing options...
BrendonMyb Posted February 17, 2010 Share hmmmmm, that is nasty - goodbye frame & so long Have to almost agree there with DB. Either the cup was too big in diameter & forced in or the cup was really hammered in with more than neccessary force creating the alu to weaken at its already weakest spot just my thoughts Link to comment Share on other sites More sharing options...
Gerhardc Posted February 17, 2010 Share ?Have I got the wrong topic? OK, I get it...this guy took a ride on the BIANCHI and then it cracked...!! Link to comment Share on other sites More sharing options...
Genesis Posted February 17, 2010 Share I hope this is not a brand new Bi%$#&i bike??Oops nearly mentioned the much hidden name of the manufacturer. Perhaps you should have photoshopped it and changed the colour as well - hahahaha!! Link to comment Share on other sites More sharing options...
levett Posted February 17, 2010 Share OK' date=' so how much abuse did the bike get to result in a crack like that? Must have been some serias downhill stuff? on a rigid fork? [/quote'] It's a road bike! Link to comment Share on other sites More sharing options...
techguy Posted February 17, 2010 Share The External crack happened first allowing the cup to flex and hence crack, Normally this will happen when the cups are not pressed in straight and it ovalises the frame createing a stress riser... Link to comment Share on other sites More sharing options...
steveO:K Posted February 17, 2010 Share You guys crack me up with your humour. Bummer techguy brought sanity to the thread with a well constructed explanation of the crack issue. Link to comment Share on other sites More sharing options...
Johan Bornman Posted February 17, 2010 Share The External crack happened first allowing the cup to flex and hence crack' date=' Normally this will happen when the cups are not pressed in straight and it ovalises the frame createing a stress riser...[/quote'] Once a cup is all the way in it is straight. I can't see how ovalisation causes a stress riser. You need a sharp point, not a gentle curve for that. Frame ovalisation at the headset is a different issue not associated with cracks. Think weld...think manufacturing steps. Link to comment Share on other sites More sharing options...
SwissVan Posted February 17, 2010 Share The External crack happened first allowing the cup to flex and hence crack' date=' Normally this will happen when the cups are not pressed in straight and it ovalises the frame createing a stress riser...[/quote'] Once a cup is all the way in it is straight. I can't see how ovalisation causes a stress riser. You need a sharp point, not a gentle curve for that. Frame ovalisation at the headset is a different issue not associated with cracks. Think weld...think manufacturing steps. I had a Peugot Tange 2 frame (Steel) many years ago, anyway...the brazing around the head tube lugs started cracking and they replaced the frame with a new one.... The new frame had to come from the factory in Europe so in the meanwhile I bought another frame... When i received the new frame from Peugot I no longer needed it and left in a friends bike shop and asked him to sell it for me... Well it hung on display in his shop window for a looong time untill eventualy someone wanted to buy it... When they took the frame down to have a closer look at it they saw it was also cracked around the head tube lugs. Frame had never been used... Link to comment Share on other sites More sharing options...
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