Cracked frame. Why?

Aluminium fatigues. Chances are the guy you bought it off crashed it or rode it more than he said. Your crash also would definitely have added to it. If it is a fatigue crack, the likeliness is other high-stress areas will start to crack. I may be wrong but this process is occurring on an old Canyon MTB I have somewhere. The headtube is cracking in the same place, the crack is about 3cm long and has 2 1cm 'prongs' at the end.

bing181 said:

One day, on a straight road and at a moderate speed with no obstacles = i.e. for no apparent reason - front end went out sideways and I fell pretty heavily..... Had my bike shop check it out after the crash, no problem.

I don't quite understand this. How can the front end go sideways without a cause? 😕

The frame looks like it just had a weak point on the headtube. It happens. The crack could have been caused by a bump in the road and the position of the crown race when it occured. The frame just couldn't take the jolt or the pressure so something had to give. It looks like it manifested itself by way of a hairline crack. It's a shame because Gios frames are known for great ride quality. Good Luck!

sogood said:

I don't quite understand this. How can the front end go sideways without a cause? 😕

Believe the crack could be due to what I've heard called "stress corrosion cracking". I've seen an old aluminum stem fail in storage due to corrosion where it clamps around the bar. In that case, the bike probably had less than 1000 miles on it.

To the best of my knowledge, this failure can occur in storage with heat-treated aluminum subjected to high "hoop stress" regardless of miles ridden. Corrosion gets a foothold in a small pit or grain-structure defect in the stressed area to start the crack, which then elongates to relieve the stress.

Possible factors could be too much heat in welding, a too-tight bearing cup (ie, excessive hoop stress), poor surface finish or preparation of the headtube (inside or out), or just a flaw in the headtube prior to manufacturing. Corrosion is accelerated in humid and warm conditions storage conditions, or of course in the presence a salt environment.

bobbyOCR said:

Chances are the guy you bought it off crashed it or rode it more than he said.

yeah, i'd be calling the guy and letting him know all about it, at least to give him a guilt trip

531Aussie said:

yeah, i'd be calling the guy and letting him know all about it, at least to give him a guilt trip

Yes, but that was two years ago .. strange it should come out now. I ride some pretty bumpy roads as well, so why not earlier if that was the cause?

As for going sideways on a straight road .. I've never managed to work out what happened.

bing181 said:

Yes, but that was two years ago .. strange it should come out now. I ride some pretty bumpy roads as well, so why not earlier if that was the cause?

As for going sideways on a straight road .. I've never managed to work out what happened.

As I said, fatigue. It loses its strength very gradually until it cracks. A crash adds significantly, normal use adds very slowly. It is inevitbale, unless it isn't ridden, for aluminium to crack.

bobbyOCR said:

As I said, fatigue. It loses its strength very gradually until it cracks. A crash adds significantly, normal use adds very slowly. It is inevitbale, unless it isn't ridden, for aluminium to crack.

A properly designed AL frame will last a very, very long time (years and years and tens upon tens of thousands of miles). One of my bikes has an AL frame; it has around 50K miles on it. You would expect fatigue failure to occur where there is some flex, like a chainstay up around the BB. The failure here is most likely due to crash damage or manufacturing/material defect.

Bro Deal said:

A properly designed AL frame will last a very, very long time (years and years and tens upon tens of thousands of miles). One of my bikes has an AL frame; it has around 50K miles on it. You would expect fatigue failure to occur where there is some flex, like a chainstay up around the BB. The failure here is most likely due to crash damage or manufacturing/material defect.

Catch 22: the bling factor dictates an alloy race frame should weigh closer to 1kg than 1.5kg & these superlight ones crack fairly regularly , the GIOS ones are generally overbuilt & pretty bombproof so I'd say you were just unlucky.

caferacerwanabe said:

Catch 22: the bling factor dictates an alloy race frame should weigh closer to 1kg than 1.5kg & these superlight ones crack fairly regularly , the GIOS ones are generally overbuilt & pretty bombproof so I'd say you were just unlucky.

Exactly. I have never encountered a GIOS in Australia, so a lack of experiance there. My bet is a crash. They seem to do alot of damage the the HT region. Look at George Hincapie.

Go the tanky 1.5Kg BMC. Stiff as a board.

bobbyOCR said:

Go the tanky 1.5Kg BMC. Stiff as a board.

I think those Gios' weigh 1300g. Pretty light for AL but not superlight. I think I would place my bet on a crash. It is just such a weird place for a crack.

bing181 said:

Hi

I have (had!) a Gios Cinquantenario alu frame. Nice bike. Bought it off a guy who raced (not much .. 4500 kms) for one season. Did one season myself - not racing - another 8500 kms.

One day, on a straight road and at a moderate speed with no obstacles = i.e. for no apparent reason - front end went out sideways and I fell pretty heavily. Hmm. Lost confidence in the bike, so relegated it to my "backup" bike. Had my bike shop check it out after the crash, no problem. Rode it for another 6 months on and off (no problem), then stripped the parts for another bike and hung it up in my cellar. I got it down recently to show someone, and was horrified to discover a vertical crack, about 15 mm long in the head tube (see photo). I'm sure it wasn't there when I hung it up before the summer, and it definitely wasn't there 12 months ago. Anyone have any ideas what could have happened? Can a frame crack without even being ridden?

Thanks. Confused ... and slightly scared. I've been doing some big descents recently.

B

I agree the crack in the headtube is from a crash -- but, more than likely it is a result of YOUR crash.

Are you in the camp that has their brake pads only a minimal, popsicle-stick width off the rim's brake surface when not engaged?

Based on the bikes bought from ONE shop (here) which some of my friends ride, some people obviously believe THAT IS THE WAY to set up a bike's brakes -- I'm not in that camp.

If you have/(had) ANY front wheel flex (BTW, all wheels flex a little!), then a momentary "harmonic" oscillation may have caused the brake pad to scrub the rim ...

Regardless, a possible reason that the crack did not show up before is because the paint lost its elasticity during storage AND the slight expansion & contraction in your cellar allowed it to manifest itself.

alfeng said:

If you have/(had) ANY front wheel flex (BTW, all wheels flex a little!), then a momentary "harmonic" oscillation may have caused the brake pad to scrub the rim ...

Hardly enough to bring someone down sideways whilst riding in a straight line. This is one whacky explanation. :eek:

Bro Deal said:

A properly designed AL frame will last a very, very long time (years and years and tens upon tens of thousands of miles).

But as a general rule, if you took four frames that were equally well designed; one al, one ti, one steel and one carbon, and subjected them to the same level of stress, wouldn't the aluminium frame most likely be the first to crack?

sogood said:

Hardly enough to bring someone down sideways whilst riding in a straight line. This is one whacky explanation. :eek:

Definitely. Especially if you consider that the wheel is stiff enough to push the resonance into the kHz range. And then, since the frequency is high the magnitude of vibration would be small.

There's also very little danger of having a break pad rubbing - it might make a small noise and slow you down a bit... Won't crash you though!

All the Shimano and Campy manuals I've seen show that 1-2 mm between pad and rim is the correct way to set up your brakes. This is to provide adequate leverage on contact and a reasonable amount of cable travel.

John Swanson
www.bikephysics.com

sogood said:

Hardly enough to bring someone down sideways whilst riding in a straight line. This is one whacky explanation. :eek:

Well, you/I would think so ...

But, you/I wouldn't have thought that Tyler Hamilton could drop his bike during the Giro while going down a straight roadway a few years ago, either.

ScienceIsCool said:

All the Shimano and Campy manuals I've seen show that 1-2 mm between pad and rim is the correct way to set up your brakes. This is to provide adequate leverage on contact and a reasonable amount of cable travel.

Well, different riders have different skills ... don't they?

The best riders crash at the most unexpected times.

Certainly, based on the recounting by the OP, the frame's handling may be suspect, but he continued to ride it for another SIX MONTHS (~4000 km) by his account until he chose to hang it in his cellar.

YOU are presuming the OP's wheel's spokes are properly tensioned ... and, even so, one may extrapolate that your presumption suggests that wheel shimmy which some riders experience while descending is a phantom experience.

1-2mm? ... I'm okay with 2mm, I suppose ... or, 2mm-to-3mm would be better, IMO.

Chalk it up to the invisible hand of _whomever_ if you don't want to presume a possible problem with the brake pad offset, the wheels, or "pilot error."

Maybe the diameter of that headset was too large for the headtube?

bing181 said:

Hi

I have (had!) a Gios Cinquantenario alu frame. Nice bike. Bought it off a guy who raced (not much .. 4500 kms) for one season. Did one season myself - not racing - another 8500 kms.

One day, on a straight road and at a moderate speed with no obstacles = i.e. for no apparent reason - front end went out sideways and I fell pretty heavily. Hmm. Lost confidence in the bike, so relegated it to my "backup" bike. Had my bike shop check it out after the crash, no problem. Rode it for another 6 months on and off (no problem), then stripped the parts for another bike and hung it up in my cellar. I got it down recently to show someone, and was horrified to discover a vertical crack, about 15 mm long in the head tube (see photo). I'm sure it wasn't there when I hung it up before the summer, and it definitely wasn't there 12 months ago. Anyone have any ideas what could have happened? Can a frame crack without even being ridden?

Thanks. Confused ... and slightly scared. I've been doing some big descents recently.

B

chainstretched said:

But as a general rule, if you took four frames that were equally well designed; one al, one ti, one steel and one carbon, and subjected them to the same level of stress, wouldn't the aluminium frame most likely be the first to crack?

The problem with this statement lies with the definition of "well designed". If by well designed meant that they are all designed to the same durability specification, then they should all fail at the same time.