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Should there be a 'safe' life for bicycle parts? - Newspaper article

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Should there be a 'safe' life for bicycle parts? - Newspaper article

Old 11-23-16, 10:54 PM
  #26  
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Originally Posted by FBinNY View Post
IMO - I can't imagine a poorer material choice for a steerer tube. (yes, that includes CF).

I agree that it's possible to properly engineer an aluminum steerer, but I don't rust the bike makers oversea to do so. More important, I don't trust that any maintenance or life cycle protocols will be adhered to.

If anyone reading this has a fork with an aluminum steerer, I suggest you replace it NOW. Failing that, consider installing a 3-4" wooden or tubular steel pin up from the bottom as a safety net.
Ok, you are clearly way more onowledgable and experienced than me and many on this site and in the industry. Thats established and accepted.

With all that said...what? You are aaying that what is basically the most common fork setup on entry level to mid level road bikes and mid level to upper level hybrids is the worst possible material choice?
All the major brands and most all the mid-sized brands are designing bikes with forks that are the worst possible combo of material?


What is wrong with the all the aluminum steerer carbon forks on the market? Meaning, what is the design flaw(s)?
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Old 11-23-16, 11:20 PM
  #27  
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Originally Posted by mstateglfr View Post
Ok, you are clearly way more knowledgable and experienced than me and many on this site and in the industry. Thats established and accepted.

With all that said...what? You are aaying that what is basically the most common fork setup on entry level to mid level road bikes and mid level to upper level hybrids is the worst possible material choice?
All the major brands and most all the mid-sized brands are designing bikes with forks that are the worst possible combo of material?


What is wrong with the all the aluminum steerer carbon forks on the market? Meaning, what is the design flaw(s)?
First to clarify a factual error. Unless there was a sea change while I wasn't looking, the vast bulk of steerer tubes are steel, with CF making up most of the remainder. Aluminum steerer tubes were a relatively short lived transition between when threadless headsets made it possible, and when fork makers went to full carbon forks with integrated CF steerers.

As far as I know, (which has its limits) few forks, if any, are currently being made with aluminum steerer tubes, including forks with aluminum blades.

As for my reasons for saying that aluminum is unsuited to the task, keep in mind that I also said that it's not the material, but how it's used that matters. Aluminum is a good material, but among other things is prone to notch failure, and doesn't handle stress risers well. It's also prone to various forms of galvanic corrosion, and corrosion metal fatigue.

So when you look at the typical construction of forks with a sharp corner transition between the steerer and crown -- exactly where stress will be highest -- you can see the potential for failure. Add that water might wick into any crevice under the crown race and attack the metal at this critical point, and a failure rate greater than steel or CF shouldn't surprise anyone.

This isn't to say that those issues couldn't be addressed and engineered around, and of course they could be. But that's not what happened, the designers simply took a proven design that worked is steel for generations and changed the material without changing the design.

BTW don'[t read this to predict vast numbers of aluminum steerer failures. The truth is that most aluminum steerers won't break. Also, because bikes enjoy relatively short useful lives before being retired, most forks simply aren't ridden long enough to worry. BUT.....
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Old 11-23-16, 11:27 PM
  #28  
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I seriously doubt, could be wrong, that cycle companies employee engineers that use strain gauges to analyze stress and then use modeling programs or use destructive testing to determine MTF. Well, at least a few decades ago, some may now.

Carbon fiber most decidedly has a useful life and is affected by impact damage and internal delamination of the layups, UV radiation and the quality of the material and quality control in the layups and exposure to high temperature, which for low temperature resins is not all that high.

I doubt most people would ever reach a life limit on an aluminum frame much less a steel frame.

The wrong material used in the wrong place is always bad, aluminum steering tubes, might be one of those places.
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Old 11-24-16, 12:04 AM
  #29  
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Originally Posted by Loose Chain View Post
I seriously doubt, could be wrong, that cycle companies employee engineers that use strain gauges to analyze stress and then use modeling programs or use destructive testing to determine MTF. .....
Could be something was lost in translation or editing, but could you please decode this.
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Old 11-24-16, 12:40 AM
  #30  
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Aluminum steerer tubes have been standard on suspension forks for 20 years and they don't cause many issues.

The only time they are a problem on mountain bikes are if the stem or headset damage them, like a collet clamp stem or headset without a top compression ring (Cough CK cough).

It's usually composite construction with a bonded steerer tube that causes issues. I have a Mongoose IBOC with aluminum fork and steel steerer that I keep an eye on, and a big ass grade 8 bolt through the fender mounting point as that will also buy you a second ore two.
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Old 11-24-16, 01:15 AM
  #31  
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Originally Posted by FBinNY View Post
Could be something was lost in translation or editing, but could you please decode this.
I long ago learned this was the most unfriendly forum on the internet and decided I do not care, I can be at least a big of a ja as anyone here. If you cannot figure it out, you have a problem that is beyond the need for decoding a simple set of sentences.

Do you not know what a strain gauge is?

Do you not understand that there are computer modeling programs to which that data can then be fed to produce simulations?

Do you not know what an engineer is?

MTF, okay, perhaps I should have said mean time to failure, I can give you that one.

UV radiation, that would be fifth grade science, ultraviolet radiation, the portion of the electromagnetic spectrum that causes sunburn.

What other part do you need translating? Can I buy you a dictionary? Because you apparently do not know how to use any of those available on the wuh, wuh, wuh.

LC
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Old 11-24-16, 01:24 AM
  #32  
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Originally Posted by Loose Chain View Post
I long ago learned this was the most unfriendly forum on the internet and decided I do not care, I can be at least a big of a ja as anyone here. If you cannot figure it out, you have a problem that is beyond the need for decoding a simple set of sentences.
ŷ
Do you not know what a strain gauge......

What other part do you need translating? Can I buy you a dictionary? Because you apparently do not know how to use any of those available on the wuh, wuh, wuh.

LC
I'm sorry that you found my request to be unfriendly. I tried to credit the problem to fast typing or editing. So let me be clearer.

It's not the words, it's the syntax. Your sentence lacks a predicate, so the reader has no idea of the point you're trying to make.

Take the chip off your shoulder and read the sentence I quoted and you might see what I mean. Then again you might not.
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Last edited by FBinNY; 11-24-16 at 01:28 AM.
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Old 11-24-16, 01:27 AM
  #33  
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here's what I posted on the parallel thread in A&S
Originally Posted by bulldog1935 View Post
By definition, all materials contain defects at some level. Fatigue is the occlusion of those defects under cyclic (repeating) stress into a crack that will grow under normal (design) cyclic stress.
That crack, which will grow at the normal stress, is defined as a critical flaw size.
Steel has the property of endurance limit, in that, at or below the endurance stress, microscopic damage will not accumulate into a critical flaw (it could at stress higher than the endurance limit). This is because of the crystal system in magnetic steels - they have limited slip systems (body-centered-cubic crystal system).
The aluminum alloy crystal system (face-centered-cubic) has many more slip systems, allowing defects to slide in the metal grains and grow together to form a critical flaw. It may take hundreds of millions of stress cycles to form the critical flaw, but as long as the cyclic loading continues, it will eventually happen.
And it could take longer than your lifetime usage of the part.

The cyclic loading can as simple as your weight on the bars cyclically changing under road vibration - just an example.
Of course rotating stress like pedaling a crank is a cyclic stress.

The moral is you should occasionally replace your aluminum bars. Unfortunately, there is no hard and fast rule about how often that should be.
But if you ride in your core muscles and don't lean heavily on your bars, it's certainly less frequently than if you do. It's also smart to inspect your bars for cracks at any machined lines or loaded edges (such as the corner of stem contact or diameter change in the bar). If you find a crack, replace the bar immediately.

btw, if you search handlebar fatigue, you'll find many articles to read, both practical and academic.
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Old 11-24-16, 01:39 AM
  #34  
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I'm usually more fatigued than my handlebars.


I wouldn't know what to say about that. There are plenty of neat Shelbys with perfectly good Donald Duck heads out there and most antique bike owners die of old age.
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Old 11-24-16, 02:06 AM
  #35  
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Originally Posted by Rollfast View Post
I'm usually more fatigued than my handlebars.
Yeah, this thread has exceeded my fatigue limit
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Old 11-24-16, 09:52 AM
  #36  
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Loose Chain, even if the companies did modeling and simulations and applied large safety margins, the actual bicycle hardware could still have problems.


As you know, everything has defects. Defects tend to dominate life and cause variability in real performance (as opposed to computer simulations of performance and life). Defects can also be induced after anufacturing (road hazards, wrenching,...).


Even if you have a probabilistic fatigue life simulation, there remains the problem of use. The real life use case is going to vary from that (or those analyzed). The use case will affect life.


I don't want any government sticking their nose in where other remedies already exist. Governments are already too pervasive.
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Old 11-24-16, 10:24 AM
  #37  
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Originally Posted by Darth Lefty View Post
BTW, researching the Pepperoni fork recall, I came across this ****** thread.

https://www.******.com/r/bicycling/c...ty_cannondale/


At this point it isn't even really the same company any more, right? Does Dorel have an obligation to recall and service bikes from legacy-Cannondale?

Edit: Well, that's a word I had no idea would be censored
Pepperoni fork ?

I have a 3.0 road bike with aluminum blades & steel steerer.

However, I see a gap at the blade-crown connection. Not sure if it was always there or not, and haven't ridden it since. I have 4 other road bikes, so I don't need it.

I wonder if Cannondale would replace the fork ?
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Old 11-24-16, 10:32 AM
  #38  
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Originally Posted by Loose Chain View Post
I seriously doubt, could be wrong, that cycle companies employee engineers that use strain gauges to analyze stress and then use modeling programs or use destructive testing to determine MTF. Well, at least a few decades ago, some may now.
I live in Madison have come across many Trek employees and engineers who live in the city. One, a former Boeing aerospace engineer, is indeed responsible for modeling Trek's frames using sophisticated finite element analysis software and more.
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Old 11-24-16, 11:54 AM
  #39  
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Old 11-24-16, 01:46 PM
  #40  
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Originally Posted by Loose Chain View Post
I doubt most people would ever reach a life limit on an aluminum frame much less a steel frame.
What's not at all clear is what value in either miles or years such a 'life limit' would have. My current road bike is a Cannondale made in '89 which was specified as having an aluminum fork and steerer (but I haven't verified it). It now has about 150 kmiles and I've been adding about 8 per year. I've had one previous experience with a steel steerer that suddenly snapped and don't wish to have another. Wondering if the wood backup mentioned by FBinNY would be effective or if a metal reinforcing tube is needed.
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Old 11-24-16, 02:04 PM
  #41  
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I don't think that a year limit would make sense, but perhaps a mileage limit, for some parts. In most cases a skilled mechanic can tell if a part is safe or not.
That being said, carbon forks bonded to aluminium steer tube is a bad idea, don't buy one.
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Old 11-24-16, 03:23 PM
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Originally Posted by Homebrew01 View Post
Pepperoni fork ?

I have a 3.0 road bike with aluminum blades & steel steerer.

However, I see a gap at the blade-crown connection. Not sure if it was always there or not, and haven't ridden it since. I have 4 other road bikes, so I don't need it.

I wonder if Cannondale would replace the fork ?
Haven't seen anything of that vintage. There was a fork recall in 1985
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Old 11-30-16, 04:33 PM
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A heads up link for those riding modern.
Recalls | Bicycle Retailer and Industry News
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Old 11-30-16, 04:57 PM
  #44  
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Originally Posted by Spoonrobot View Post
When was the last time a carbon threadless fork was made with a steel steerer? Has this combo ever been available?

I've only ever seen carbon/aluminum or carbon/carbon combinations. Am I missing something? I thought carbon/aluminum was the most common fork combo produced in modern bikes?
My Wound Up carbon fork (1" threaded) has a steel steerer.
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Old 11-30-16, 06:56 PM
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I think the vast majority of modern carbon forks are made with aluminum steerer tubes and not steel. Previous posts in this thread had me questioning my experience but after looking at every bike in the shop I'm pretty sure other posters were mistaken. I know the difference between cutting steel and cutting aluminum steerers with a hacksaw and I've only ever done the former on my personal bikes. All the dozens of other forks I've cut at work have been aluminum.



For example; almost all the forks listed on the nashbar page are listed with alloy or aluminum steerer. This is just an example:
Fox 32 Float 27.5 140mm Suspension Fork with CTD and Trail Adjust -- 15mm QR
STEERER 1.5 - 1 1/8" Tapered aluminum

And a selection of Diamonback models
Diamondback Bicycles - Diamondback Bikes, 2016 Haanjo Comp
DB Gravel Disc Carbon Leg, 1.5" Taper Alloy Steerer Disc Fork
DBR Podium SPF Airformed Alloy, Bladed Legs, 1.5" Alloy Taper Steerer Tube, w/ Flat Mount Disc Tab
DBR Podium Airformed Disc Alloy, 1.5" Taper Alloy Steerer
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