Now that is funny! :lol:

Did I mention I lived IN San Francisco in the 60s?

:rolleyes:

I was riding a bike in 1949. Now I ride 2 road bikes, both have carbon fiber frames, forks, and steer tubes. :)
Rode 4706 miles in 2012 before the flu stopped me.

I'll lift my glass to that.. CONGRATS! Beat me my 600 miles... albeit I missed 3+ weeks with a bad cold.

GENTELMAN's: Tone of this thread is heading far south.. c'mon. Reminds me of an old tale I heard living in the sandhills of NE back when. Couple of bar flies get a load of brew onboard... go behind the establishment.. and see who can whiz into the strong north wind w/o getting their jeans wet. Give it some rest.............:thumb:

Anybody know someone who works at a LBS who has to replace the recall forks? What I wonder.. what's the main problem/s with why their recalled? Those recalls more a function of rate of manufacture.. or design?

Some frames are made from magnesium or alloys with magnesium in them.Magnesium is very flammable so I won't ride them due to the risk I 'd catch fire....what was this thread about again? Oh nevermind.

That's sort of true. It's only flamable in powder or shavings...not frames or blocks.

This reminds me of all the old stories of why a VW engine catches fire so easy...I am sure it had nothing to do with plastic fule filters and pumping gasoline into a into the engine compartment!

Being tandem riders and having pedaled over 230,000 miles on tandem bicycles since 1975 we have had only one bad experience with a fork.
It was steel (Reynolds custom 531) and broke/failed at 13,000 miles.
Together we tip the scales at 238 lbs so we are right in your weight category.
Currently have 34,000 miles on carbon fiber (Alpha Q) fork on our full carbon fiber tandem.
Have also broken 2 steel tandem frames. One break at 50,000 miles and the other at 56,000 miles.
Have ridden steel alloys, aluminum, titanium, carbon fiber and bamboo bicycles.
Amy material will eventually fagtigue/fail/break.

Bold mine.

That is rare.. very. Unless one gets said slug shot into them... the kind of instant 'lead posioning' that kills.. slug's effect. Sometimes slugs are left inside a body.. with no apparent ill effects. I know of the old timers who shot tons of lead bullets in an ENCLOSED environment.. and they all tested LOW for lead levels.

One has be completely ignorant and careless to get real lead levels up.. like in the 2nd case mentioned.

Ok Very basic Chemistry fans,


Mg, is diffrernt from Mn, and Mo.

atomic #s 12, 25 & 42 1 each in Period row, row 2, 3 & 4

as I recall Reynolds 531 alloy is C, Mn, Mo, in of course, Fe.

The phrase acute lead poisoning doesn't refer to a toxic event. It's a play on words referring to being shot, ie. infused with lead and suffering immediate ill effects or death.

In any case metallic lead is rarely toxic. It's various oxides and organic compounds of lead that toxic. If lead is left in the body, it tends to become encapsulated and not dissolve into tissues or the bloodstream. Generally lead poisoning is a slow chronic process as small doses accumulate in the body. You can do this ingesting lead shot, but the more likely causes are lead dust, or ingestion of lead oxides. Dust is a problem because the small particle size is easy to inhale and the increased surface area makes for rapid oxidation.

An interesting occupational lead risk is to dive shop employees. The constant stacking and banging of lead dive weights flakes the surface oxide into fine dust which is then inhaled.

That's the thing - titanium and steel (and alloys thereof), do not fail due to fatigue if the stresses are kept low enough, unlike aluminium and magnesium (and alloys thereof), which will eventually fail by fatigue regardless of the magnitude of the stresses.

Magnesium, manganese and molybdenum.

And all three are used in bikes - 531 is a manganese-molybdenum alloy steel, 4130 is chromium-molybdenum alloy steel, and magnesium alloys have been used for bike frames, so it's no wonder the names are getting hurled about.

But that's a bit like saying to a weight lifter that he will never injure himself as long as he doesn't lift more than X amount of weight. Obviously steel and ti are very good frame materials, as are others, but the "no fatigue limit" characteristic of those materials is obviously only a part of the equation, because steel and ti frames do fail from fatigue sometimes.

I was told by my materials lecturer (I'm a first-year mechanical engineering student) that a lot of structures aren't designed to always keep the stresses below the fatigue limit, because they'd be quite a bit heavier if they were. I'm not sure traditional steel frames and forks are "designed" in that sense anyway, but if I was designing a fork that I was going to be riding, I might put up with a bit of excess weight in order to keep the stress below the fatigue limit for a decent proportion of the time. I don't know if that's actually how manufacturers do it, though.

I think you've hit on a key point in mentioning weight concerns and restraints.

Me too, but given the typical endurance limit for steel 10^7 to 10^8 how much riding would it take to stress a fork beyond the fatigue limit that many times? The fatigue limit for steel is roughly around half of its tensile strength right? (I'm not in a materials class, so seriously.) If that's right then it takes pretty big jar to pass that limit. Doing that 10 million times I think you'd have to be riding rough trail really hard, eight hours every day, for ten years. So it's not really a factor we'd need to worry about much imo, for steel.

Too late on the patent..http://bikeforums.net/attachment.php...hmentid=293759

I'm not sure what the fatigue limit actually is - the notes from that lecture aren't somewhere I can get to them easily. Also, that was only talking about mild steel, not alloy steels, and I'm not sure if the fatigue limit of an alloy steel is dependant on its tensile strength directly, or if it's more complex. I suspect the latter.

I'm not even sure how I'd work out the force on a bike fork anyway - it's not just related to rider weight and road quality, obviously tyre pressure is a factor, but then there's the weight distribution of the rider to take into account, then there's extra force from braking and turning, and probably a lot else. It would probably be easier to start with a strain gauge on the fork and work back from there.

this steel frame is about the strongest and sturdiest bicycle frame I've ever ridden. I believe these are Tange frames, made by Miyata. its from late 1983. the wheels are really strong, too, the rear wheel was made with 0 dish, the axles are solid hardened steel. I did endless drops, curb hops, staircases, as well as all sorts of stupid forest tricks on this bike. that /is/ a replacement front wheel, the original got bent by a car.

http://www.hogranch.com/digi-2007/20...s/IMG_9137.JPG

my point is, not all steel is the same. neither is all aluminum. or anything, really.

My limited understanding was that fatigue limit is generally in the range, 30-60% of tensile strength, for whatever variety. I'd be surprised too if they were directly related. But anyway the alloys would take even longer to fail, no?

My musings on the fatigue failure of a steel fork were rough handling and a lot of time are necessary, not to say exhaustive. In other words, intuitively we don't ever reach the fatigue limit for steel in normal riding so fatigue failure, without something like crashes or stunts, is rare.

As you know, aluminum is a different story, not really having a fatigue limit. Who really knows with carbon fiber, so little data available and so much depending on how it's constructed. I've almost talked myself into replacing my cf fork here :eek:

It depends, if you double the tensile strength of your steel by going from mild steel to some super-steel alloy, but only multiply the fatigue limit by 1.6, then you'll be operating the material past the fatigue limit more of the time, assuming you lighten the structure by removing material to make use of the greater tensile strength. It all depends on exactly how the two properties are related.

Anyway, you're preaching to the choir here, so to speak. My initial post on the subject was in response to someone saying that all materials will eventually fatigue and break, which you agree isn't necessarily true.

Normally you'd alleviate that with larger diameter tubes. The problem is the "beer can effect" - you want wider or the same diameter tubes so that it doesn't get whippy, and so the walls get thinner if you reduce the amount of steel. Too thin and they crumple too easily. Thus you can't just lighten the structure in proportion to the tensile strength. But stronger alloys can be both lighter and stronger, just not in proportion.

I thought you were saying that steel forks would fail eventually but I think your clarification is probably correct. It's conceivable for steel forks to last indefinitely assuming normal use.

I was more than half serious about replacing my CF fork with steel. It has a small flaw near the right drop-out, a notch maybe a millimeter or two deep that I didn't notice when I got it new but saw shortly thereafter. I put about 6000 miles on it last year and it's really been bugging me that I have no way of checking whether the material has been weakened. Maybe I should post pics for opinions since this is a frame material thread.

Bold mine. Whose going to send out for popcorn.. then? :D Good idea IMO though... need a good clear pic I'd suggest.

Back when in this trail.. someone reminded about this actually being about FAILURE MODE. :thumb: Right on.

Possibly I missed remarks per aluminum's failure mode. In the end.. I'd think some bending.. advance warning per performance prior to winding up on your face [?].

I don't know.. are all al forks solid metal.. or some hollow tubed?

All are hollow tubed.

Is this the beginning of the end of the world as we now know it ?
 

Will the discussion on bike frame and fork materials bring on the zombie apocalypse ?:wtf:

I enjoy going into "the 41" and reading about frames breaking

Is it something in the water, or a contagion that has swept the forums ?............film at 11.

The news at 11...........ouch.
 

#!

IF your tolerance level for others is so low.. maybe you should take a vacation. ;)

Search function is mostly a non starter around here... mostly all salad which is the norm here. Like mining for gold.. tons and tons of dirt to get a day's wages. Someone who actually knows something might eventually respond. I know.. rare around these parts.

Define "knowing something" in this context... what are you actually looking for?

Right.. two--- shayyy.

Expert in how their fabricated... someone with long experience actually replacing them.

............if you want to search something, I get much more meaningful results with Google, using the subject and a limit to Bike Forums..

It almost always kicks up a number of threads that you can then access directly.