Casati Gianni Passat
 

I just left my buddy in the hospital w/ facial lacerations broken fingers and unknown other injuries. His Casati is sitting in my living room with a columbus coderis laminati crome fork that has a definate folded crease 1/4 inch from the tailing point of the fork crown (back side of the fork - left side). He was riding with my wife this evening on clear, dry, smooth roads travelling about 20mph when the bike stopped and he sailed over the bars. The only explaination i can come up with is that the fork fatigued and the tire jammed against the sloping down tube. Has anyone heard of this happening before? was there ever a recall on these forks? I'm just trying to figure out what happened.

Hello selospa, do you have photos of the fold/crease?

East Hill

i don't have a photo. he is home from the hospital and i delivered the bike back to him, but i'll see if he can email a pic to me. It is difficult for me to determine if the fork crease was the cause of the accident or caused by the accident, however barring any other explaination i'm inclined to suspect that the fork failed causing the accident. i'll try to forward a photo.

I thought about this for a while before I slept last night and, it seems to me that the culprit could be either a broken axle, broken QR skewer, or the one that impressed me most: A broken hub flange. Any of these would send the wheel to one side hard enough to stop the bike cold. The flange though, that would collapse the wheel in such a way as to best explain what you've described.

Danny

I wish him a speedy recovery. Was this a bike that was in otherwise "good shape?" What is the model year of this frame/fork? Was there any rust on the fork? Does your friend surpass the "recommended weight" for the frame by a wide margin? My guess is that there was an unnoticed crack there that snowballed into a failure?

i checked the wheel and it was in good shape. no broken spokes, the QR skewer and axel were un damaged. with the exception of the fork, the bike post-accident seemed to be in relatively good shape other than the wheels being out of true due to impact of the landing. in fact the rear wheel was in worse shape than the front. i could not see any visual indication of frame damage.

the bike is a mid 1990 vintage (my guess) casatti model gianni passat. the fork is an all chrome columbus fork with no evidence of rust visible from the outside.

Headset remarkably loose then?

Danny

a steel fork does not fail in the manner you describe. they may crack & break ,normally at the steerer or just below the crown, or bend *forward* due to the head angle & fork rake /offset. bending rearward can only happen from a frontal impact ,or something violently jamming between the fork blades or crown.
personally, the description of events sounds to me like another "i was just riding along... when all of the sudden..." CYA stories. considering that the wheel/tyre are intact and that there's no obvious component/mechanical failures such as the front brake caliper,my vote is that he either picked something up off the road which jammed behind the crown or the road was not as smooth or clear as described- perhaps a stick,etc.,a pothole,maybe even catching a drain grate.

thanks for your thoughts. i agree with your assessment that one would expect a fork to fail - if it were to - in the direction of the rake and that a crease at the back of the fork would be indicative of an impact (suggesting the crease is the result of the accident and not the cause). i just baffeld by what could have caused the accident as described by my buddy and my wife.

for an incident with a force strong enuf to pitch a rider over the bars, i would normally assume a lock-up at the front .
however, it's not inconceivable that the culprit might possibly have it's source at the rear wheel . perhaps his freewheel/freehub ratchet pawls aren't functioning properly ,causing the chain to wrap itself around the cog and bind (ie- " chain suck ")?- the result would be an almost instantaneous & violent lock up of the rear.if his speed were high enuf(~ 20mph definately qualifies), the accident might happen so quickly that it wouldn't be recognised as a being initiated by a skid. an observer would probably not catch the first milliseconds of the accident,and only see it's aftermath.

A new twist, possibly applicable to this incident, that I found in my travels:

http://www.cyclingforums.com/showthread.php?t=26873

Read the entire thread, it's pretty wild stuff. Here's the reply it's centered around (by Jobst Brandt FYI):

>>>Thomas Hood writes:

> Just curiousity but could you explain what you mean by "abrupt transition" and "feathered"?

The fork crown that Cinelli among others made popular due to its aesthetic shape, is solid steel
(not hollow) as most fork crowns previously were. Typically the steer tube and fork blades
overlapped and had a band-like structure that enveloped all three tubes as we see on a Masi for
instance. The detail of that crown had features that even without feathering the crown to a smooth
transition, made it in effect the same, similar to the filigree on Singer lugs. These in effect make
a soft transition.

The Cinelli crown has fairly thick lug extensions that go inside the fork blades and end abruptly
(because no one can see this) and out of sight out of mind. However, fork blades fail in fatigue at
this transition, breaking off after an insignificant life duration. As I said, I had tow of these
failures and insisted on an external crown that was filed to have a zero thickness transition. This
has worked for many more miles than any of my Cinelli forks survived.

> "Cinelli sloping crowns....are failure prone at the abrupt transition from fork blade to the
> internal lug of the crown that cannot be feathered to a gradual transition as an external
> lug can."

> By abrupt transition I assume you meant that internal lug looked like the LCO4 shown here:

> http://www.ceeway.com/Fork-Crowns-2.htm

> I.e. the end of the lug is perpendicular to the blades and straight.

Only LC19 has a reasonable shape, and crowns of this design were made for road bicycles. Fork blades
are thinner and lighter than any of these other designs that shorten the fork blade and reach down
to tit with a heavy steel crown. It's all fashion BS.

> However it would appear the Cinelli crown's end is not like this:

http://www.ceeway.com/Fork-Crowns.htm

> The Cinelli SCA, Everest C60, C61A, C63, Columbus MAX all seem to share this. Do these not have
> 'internally feathered' ends or have I misunderstood you?

Not at all. The SCA stops abruptly and that is where fork blades fail.

> The reason I ask is that I have just acquired an almost new Mercian fillet-brazed Reynolds 653
> frame with said crown. Stunning craftsmanship; the guy I bought it off had too much money to spend
> and had just 'upgraded' to a giant carbon fibre compact!?! I'm not complaining he sold it to me
> for £75 including a record f/mech and titanium seatpost. However after reading your 'colostomy'
> incident story I'm a bit wary of that bit...

Well, I don't know what you are planning to do with it. Most collectors items don't get a lot of
miles and are specifically held for their beautiful workmanship.

The colostomy incident was a seat post failure, not a fork problem.

Jobst Brandt jobst.brandt@stanfordalumni.org Palo Alto CA<<<<<

how so...??? i read nothing contained within your linked thread that relates to this incident. could you point out whatever it was that caught your attention?

I love how whenever I do hours of research and support what I find with photos and quotes, the work seemingly always attracts at least one comment like the above So aterham, here's for you:

OP writes:

>>definate folded crease 1/4 inch from the tailing point of the fork crown (back side of the fork - left side)<<

Photo shows internal lugs of fork crown extending down into fork leg at approximately .5 inch.

I write that this referenced 'fork failure' thread is "possibly" pertinent to this thread we're now participating in.

You got a problem with that?

Danny

An in support of what you've written above:

http://yarchive.net/bike/fork_failures.html

To which I might reply that should the wheel be forced to a stop by either a failure the crown, one or the other blade, or one of the dropouts breaking, you would see the fork jammed backward and be left with thi result. It's also possible that the guy didn't have the wheel properly installed within the fork.

Danny

-you added photo attachments of the cinelli crown after my post- i don't understand why- please explain
-the links that i attempted to open from within your referenced thread all resulted in 404 not found's
I have no *problem with that* per se but i asked because even after perusing the entire reference thread i still have no idea what your point is. as i read the referenced thread, the discussion centered around the potential of a stress raiser to be introduced by the use of an insufficiently prepared cinelli-style investment cast crown of the type using internal lugs. a number of opinions were voiced, some in support and some refuting and/or further qualifying the topic.

our op states that there are no signs of failure to the fork crown and no breakage or separation of the blades- just that one blade is notably bent backwards and with a crumple/deformation zone just below the crown on the *rear* of the blade as one might expect of any fork crown design, whether internal or externally lugged.

>>>you added photo attachments of the cinelli crown after my post- i don't understand why- please explain<<<

I'm still researching what I've posted and and I'm updating my posts as I go. I'm not sure why you feel I owe an explanation for it.

>> -the links that i attempted to open from within your referenced thread all resulted in 404 not found's <<

I'm not responsible for the upkeep at Cyclingforums and so, have no idea why this is. If you're asking if what I've offered is 'real', it's only a Google search away. (And why would I go to the trouble to invent it?)

>>I have no *problem with that* per se but i asked because even after perusing the entire reference thread i still have no idea what your point is.<<

What we're answering to is a mystery, as described by the OP. Possible explanations were asked for specifically and thats what I've offered from the start. The fork crown failure thread interested me in the search because it offered much I've never read before. Fork failure is pertinient to this thread because of the OP's suspicion that this is what cause the crash.


>>>>the op states that they're are no signs of failure to the fork crown and no breakage or separation of the blades- just that one blade is notably bent backwards and with a crumple zone just below the crown on the *rear* of the blade as one might expect of any fork crown design, whether internal or externally lugged.<<<<<

True enough but the OP was severely stressed when he wrote the OrigPost and the bike was gone from his possession rather quickly after that Orig Post was made. He's made it clear, via what he's posted that he's not versed in what can go wrong in cycling, much less what did and It's likely that signs you or I might consider obvious were missed in the translation.

Without photos, all speculation is fair game. That said, I'm a bit pissed by your trying to displace regard for what I've posted by questioning it's relevance. It's up to the readers of the thread to decide that. Not you.

Danny

bike forks fold backward from frontal impact or picking up something in the wheel that jams against the back of the fork. I thrashed a suspension fork once by catching a big stick in the spokes. The road forum has a recent "squirrel in the forks" thread that has interesting pictures of, um, squirrels in forks and the resultant damage. It clearly wasn't an alien death ray, and whatever caused the wheel to cease rotating is apparently gone missing. BTW, the fork will probably fail in accordance with any stress risers that were built into it at creation: if the cinelli crown introduces stress risers, then the failure will reflect that, but the fork crown most likely did not cause the failure...there are about a gazillion bikes using that crown every day, and I haven't ever seen or heard of a crown-related failure before (that doesn't mean that the crown did not cause the failure, only that I would look for more everyday causes before seeking a rare solution to the puzzle).

I honestly have never seen a fork fail from fatigue or weld failure in action. I have a small collection of forks that had at some time in the past been crashed and probably should have failed, but didn't, and I replaced 'em with something better. A Bianchi with a crack in the steel traveling upward from the dropout three or four inches, a couple of treks with cracked or badly swollen steerer tubes, a suspension fork that had the shock legs wear the fork crown oblong. None of 'em failed in action.

Have you disassembled the headset/fork to see if there is damage to the steerer tube?

Listen, I'm just trying to be more helpful to the OP than most would entertain. I feel badly for the guy (and the accident victim) and I'm giving him some quick research to consider in his search for an answer. You, OTOH, are offering what you know to be true ,but without relevant support, and are now trying to turn the attention of the readers from the pertinient to the personal. I'm not a problem, the problem, the cause or the solution. I'm just offering what I can to help.

In answer to this:

>>our op states that there are no signs of failure to the fork crown and no breakage or separation of the blades- just that one blade is notably bent backwards and with a crumple/deformation zone just below the crown on the *rear* of the blade as one might expect of any fork crown design<<<

I say look above this post by two or three and you'll see that I've answered it already. I'll reword it to make it a tad easier for you to understand:

The fork of a bike is a sub-system assembly that is co-dependent on all of its various parts (tire,tube,rim,rimtape,spoke heads, spokes, hub flange, axle, QR, dropouts, blades, crown, braze, steerer, headset, stem bars, etc.) to form a reliable, functional front end system. A failure, or a load borne deformation anywhere along the chain of sub-assemblies will cause an excessive load to be placed on the next load bearing link in the chain. Evidence of which part of the chain failed first will probably be seen in that area if you know what to look for and if the next part of the chain isn't overtly substantial
, in which case said evidence will end up later along the chain.

My initial opinion was that the hub flange, QR or the axle had broken. I said that because, if the wheel were to jam within the fork blades and cause one to be bent whilst the other were more/less intact, it would seem to me that load bearing was one sided, as caused by the wheel tilting to one side before being jammed to a stop within the fork assembly. A failure though, in the elastic strength of one of the fork blade could cause the same thing. Hence the reference to the Brandt threads.

If that explanation isn't enough for you, then someone more patient than I will have to help you through it.

Danny

i greatly appreciate all of your input and response to this posting. i realize that i've provided little information for more than speculation here. the bike is currently at a LBS for a thorough inspection and i will post any conclusive results of that inspection (if there are any) when i hear back. initial discussions w/ my LBS confirmed what many have said here, a failure at the rear of the fork seems to imply damage from some type of frontal impact - but i hope to have more info in a week or so.