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Performance deterioration with Ti frame?

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Performance deterioration with Ti frame?

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Old 09-16-09, 09:49 AM
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Performance deterioration with Ti frame?

Main question: is there any (negligible or otherwise) performance deterioration over time with a Ti frame?

Somewhat unnecessary details behind the question...

I'm looking at purchasing a new road bike. Have narrowed it down to either Madone 5 or Lynskey R330. I'm currently riding a Dean El Vado (my first and only road bike). It's more a touring geometry. Since getting it last summer, I've really become addicted to cycling. Now I want fast.

My bike mechanic maintains that ALL frames will eventually show some deterioration after so many miles. Yet, many Ti frame builders maintain there is none. Is that marketing hype, or is there truth to it?

Of great help would be input from long-time Ti frame owners. and particularly Lynskey owners. Have you noticed any performance difference with how your bike rides now and how it rode on day one?

Any Lynskey R330 owners who have switched from carbon? Comparisons? Likes? Dislikes?

Thanks in advance,
John
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Old 09-16-09, 10:04 AM
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I have a '97-'98 GT forte. About 4 years ago, I almost became irratated with an LBS owner who told me that I didn't need a new frame, thus keeping me from going to my wife with that excuse for a new one.

I've seen no deterioration in performace with the bike - on the other hand, the engine....
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Old 09-16-09, 10:22 AM
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I know this doesn't exactly answer your question, but hope it puts some of your worries to rest. I have a '94/'95 Cannondale M400 (Aluminum mountain bike w/rigid front fork). This bike has gone through many miles on rocky trails and numerous falls/flips/crashes.... and is still going strong. If an aluminum frame mountain bike frame can last this long and still be going strong, I'm sure your titanium road bike will hold up just fine.
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Old 09-16-09, 10:38 AM
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http://www.sv.vt.edu/classes/MSE2094...y/fatigue.html



As long as the fatigue limit (max stress for a given number of cycles) of Steel and Ti is not met, you have nothing to worry about. Al has no limit, meaning that no matter the stress applied, it will only last a definite amount af cycles... but most Al bikes are designed in such a way that we'll never see that failure of material.
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Old 09-16-09, 11:08 AM
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Originally Posted by silversx80 View Post
http://www.sv.vt.edu/classes/MSE2094...y/fatigue.html



As long as the fatigue limit (max stress for a given number of cycles) of Steel and Ti is not met, you have nothing to worry about. Al has no limit, meaning that no matter the stress applied, it will only last a definite amount af cycles... but most Al bikes are designed in such a way that we'll never see that failure of material.
On a similar note, anyone who thinks that normal riding doesn't commonly exceed the fatigue limit for a typical lightweight steel or Ti frame is smoking crack. ALL frames accumulate fatigue, and all frames are designed to account for this.
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Old 09-16-09, 11:14 AM
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Well made Ti frames will last indefinitely without performance degradation. My Ibis Ti Road is now 13 years old and probably has about 50,000 miles on it. Rode it this morning. Still feels brand new.

From a longevity standpoint, CF can't touch Ti. And nothing really feels quite like a good Ti bicycle. I have two of them, in addition to CF bikes. Still love the Ti.
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Old 09-16-09, 11:26 AM
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Originally Posted by [email protected] View Post
Main question: is there any (negligible or otherwise) performance deterioration over time with a Ti frame?
Off the top of my head, wear will erode some material from the frame making it lighter. This will result in a performance increase. The magnitude will be completely negligible. I'm sure there are many other insignificant changes that occur with use. Now why do you care?
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Old 09-16-09, 11:28 AM
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Originally Posted by grolby View Post
On a similar note, anyone who thinks that normal riding doesn't commonly exceed the fatigue limit for a typical lightweight steel or Ti frame is smoking crack. ALL frames accumulate fatigue, and all frames are designed to account for this.
Ummmm, frames are designed to account for fatigue by designing the frame to not commonly exceed the fatigue limit. BTW, a single stress is not fatigue (i.e. hitting a bump). Repeated cycles are fatigue (i.e. pedaling). The more cycles, the lower the stress limit.

Edit: When fatigue limit is exceeded, materials fail. Plain and simple. It's usually stress fractures or plastic deformation.

Originally Posted by patentcad View Post
From a longevity standpoint, CF can't touch Ti. And nothing really feels quite like a good Ti bicycle. I have two of them, in addition to CF bikes. Still love the Ti.
So true. After 25K mi on the Scott, a custom Ti will be on order.

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Old 09-16-09, 12:20 PM
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Originally Posted by silversx80 View Post
Ummmm, frames are designed to account for fatigue by designing the frame to not commonly exceed the fatigue limit. BTW, a single stress is not fatigue (i.e. hitting a bump). Repeated cycles are fatigue (i.e. pedaling). The more cycles, the lower the stress limit.

Edit: When fatigue limit is exceeded, materials fail. Plain and simple. It's usually stress fractures or plastic deformation.
Incorrect...



Where are you getting this stuff... When fatigue limit is exceeded, it's usually plastic deformation??? Seriously?
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Old 09-16-09, 12:26 PM
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Originally Posted by Phantoj View Post
Incorrect...



Where are you getting this stuff... When fatigue limit is exceeded, it's usually plastic deformation??? Seriously?
My mistake - stress fractures. Edit: propagating stress fractures.

I forgot to delete that part before clicking the post button.

Quick reference:
http://en.wikipedia.org/wiki/Fatigue_limit

Fatigue limit, endurance limit, and fatigue strength are all expressions used to describe a property of materials: the amplitude (or range) of cyclic stress that can be applied to the material without causing fatigue failure.[1] Ferrous alloys and titanium alloys [2] have a distinct limit, an amplitude below which there appears to be no number of cycles that will cause failure. Other structural metals such as aluminium and copper, do not have a distinct limit and will eventually fail even from small stress amplitudes. In these cases, a number of cycles (usually 107) is chosen to represent the fatigue life of the material.


I can pull out my old college materail sciences books when I get home if you'd like
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Old 09-16-09, 12:27 PM
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Originally Posted by patentcad View Post
Well made Ti frames will last indefinitely without performance degradation. My Ibis Ti Road is now 13 years old and probably has about 50,000 miles on it. Rode it this morning. Still feels brand new.

From a longevity standpoint, CF can't touch Ti. And nothing really feels quite like a good Ti bicycle. I have two of them, in addition to CF bikes. Still love the Ti.
I thought you cracked a Ti frame, think it was a Merlin..? Am I confused?
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Old 09-16-09, 12:56 PM
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Originally Posted by [email protected] View Post
Main question: is there any (negligible or otherwise) performance deterioration over time with a Ti frame?

Unless it cracks, no. You won't feel a difference. Same is true of steel and carbon fiber.

Buy a bike with a lifetime warranty, from a reputable manufacturer who will still be around in 3-5 years when you need warranty service.
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Old 09-16-09, 02:17 PM
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I had a Lynskey R320 and now have the R330. I like the R330 better in some ways, miss the R320 in others. I have a Clark Kent F-14 mtb from 1994 that I have beaten the heck out of. It still rides like I just built it up. Stiff when it need to be and comfortable all the time. You can't ask for more from a well made Ti frame. It will last you a lifetime and if you get tired of riding it, the only reason is that you believe the hype that another material is "better". I have a top end carbon frame, a few steel frames, and a scandium frame. They all make me happy on any given day, but if I had to pick a forever bike both from a ride AND durability standpoint I can't beat my Ti.
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Old 09-16-09, 02:36 PM
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Originally Posted by silversx80 View Post
This is a good reference; it explains that the term "fatigue limit" is not always used consistently - some use the term to refer to the endurance limit, some use the term to refer to the stress required to cause failure for a particular number of cycles.

You're using it in both ways:

Al has no limit, meaning that no matter the stress applied, it will only last a definite amount af cycles...
(endurance limit)

(max stress for a given number of cycles)
(stress requred to cause failure for a particular number of cycles)

Interestingly, the wiki link concludes with, "However, recent research suggests that endurance limits do not actually exist, that if enough stress cycles are performed, even the smallest stress will eventually produce fatigue failure." The endurance limit is a myth!
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Old 09-16-09, 03:06 PM
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Originally Posted by Phantoj View Post
This is a good reference; it explains that the term "fatigue limit" is not always used consistently - some use the term to refer to the endurance limit, some use the term to refer to the stress required to cause failure for a particular number of cycles.

You're using it in both ways:

(endurance limit)

(stress requred to cause failure for a particular number of cycles)

Interestingly, the wiki link concludes with, "However, recent research suggests that endurance limits do not actually exist, that if enough stress cycles are performed, even the smallest stress will eventually produce fatigue failure." The endurance limit is a myth!
Throughout my college education, none of my professors had used any differentiation (endurance v fatigue limits), so I tend not to as well.

The interesting thing about the endurance/fatigue limit testing done in that last comment, is that it was done in the ultrasonic range (20kHz) to produce a 10^10 cycle loading. While this is great to get data, fast, I'm left wondering about the scalability to longer load cycles, time wise, as well as the other parameters of the tests (heat generated, if any, from the loading is a big one). Either way, if a bicycle is properly designed to have a 'lifetime' of fatigue loading - as long as it is not operated beyond its design limits - I doubt that we'll ever see fatigue failure, nor a decrease in structure strength and performance from fatigue loading.
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Old 09-16-09, 04:02 PM
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Whether the steel and titanium alloys used to make bicycle frames have a technical endurance limit is a nice theoretical question that metallurgists can argue and write papers about. But from a practical standpoint it's clear that any frame made of those materials will be subjected to forces in excess of the endurance limit routinely in the course of normal cycling. So keep using a steel or titanium frame long enough and eventually there will be a fatigue failure (and the same is true of aluminum and carbon fiber). But with well made frames that are not designed to push the limits of lightweight of any of these materials that fatigue failure is unlikely to occur before the frame is retired from use for other reasons.
[Current bikes: steel tandem - 42 years old - suffered one failure to date (repaired); steel folder - 17 years old - suffered one failure (repaired); steel recreational frame - 40 years old; aluminum race frame - 20 years old (> 100000 miles); steel tourer - 25 years old]
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Old 09-16-09, 04:14 PM
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Originally Posted by Phantoj View Post
I thought you cracked a Ti frame, think it was a Merlin..? Am I confused?
That was my 1991 Merlin, yes it cracked in two places with about 30K miles on it. The Ibis is really a much higher quality frame, better tubing (3/2.5 butted tubing, higher quality build).

Ti performance won't degrade, as long as it doesn't break. Once it breaks you fix it or leave it out with the trash. I did the latter with the Merlin. The vast majority of Ti frames don't break, but in all fairness, VERY few actually get ridden 30-50K + miles like the bicycles I have owned. My guess is that 95+% of Ti frames will not break even if ridden hard 50-100K miles and will retain all their favorable performance characteristics.

I have a bunch of bicycles now, so my Ibis Ti Road only gets ridden 3000 miles annually (approx). I use it as my foul weather bike, so it sees a fair amount of rain, muck, road salt, etc. But I think with the reduced usage it may last me another 13+ years. As long as it works I'll keep it on the road. Love how the bike feels, and it's relatively light (built up bike is only 17 lbs and change).

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Old 09-16-09, 04:51 PM
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Originally Posted by prathmann View Post
Whether the steel and titanium alloys used to make bicycle frames have a technical endurance limit is a nice theoretical question that metallurgists can argue and write papers about. But from a practical standpoint it's clear that any frame made of those materials will be subjected to forces in excess of the endurance limit routinely in the course of normal cycling. So keep using a steel or titanium frame long enough and eventually there will be a fatigue failure (and the same is true of aluminum and carbon fiber). But with well made frames that are not designed to push the limits of lightweight of any of these materials that fatigue failure is unlikely to occur before the frame is retired from use for other reasons.
[Current bikes: steel tandem - 42 years old - suffered one failure to date (repaired); steel folder - 17 years old - suffered one failure (repaired); steel recreational frame - 40 years old; aluminum race frame - 20 years old (> 100000 miles); steel tourer - 25 years old]
Not quite. I think you're mistaken on what, exactly, the definition of a fatigue/endurance limit actually is. Yes, forces will exceed that limit, on a singular-level (so not exactly to exceed the limit). Impact, for example, isn't as much of a cycle (no pun intended) as pedal forces. The limit refers to the repeated stresses the material can endure before you get fatigue failure (fractures in the material). Once you hit that limit, the material has essentially failed and those cracks will continue to propagate until catastrophic failure.

So, the point is, the higher the stress, the lower number of cycles the material can endure at that stress. If the stress reaches yield strength, you'll have plastic deformation of the material. Fatigue limit is not a singular force/stress capability, but rather a curve relating number of cycles to stress levels.

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Old 09-16-09, 04:58 PM
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Get a ti frame with a lifetime warranty. The Lynskey would be great. As would Merlin, Litespeed, Serotta, Seven, etc.
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Old 09-16-09, 05:42 PM
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I have a 2001 airborne zeppelin with probably 25,000 or so miles. On much of that i weighed over 200 pounds. Other than the stickers slowly disappearing, there is negligible wear and it feels as it did day one.
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Old 09-16-09, 05:43 PM
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The OP is concern about performance deterioration not catastrophic failure. There is empirical proof of the possibility to engineer machine parts that suffer no structural integrity degradation over what is relatively an infinite number of cycles. Aeroplanes stand out in my mind as such an example.

A "spring" is defined by recoil. Corrosion is really the only factor of malfunction.

Road bikes, being designed to be "stiffer" at the crank, should be well within tolerances.
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Old 09-16-09, 05:52 PM
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Humans have on average a 7-12% perception-of-difference threshold in most regards. i.e. 6 pounds is lighter than 7 pounds but 12 pounds is the same as 13.

Given that sort of slop I doubt you'd notice the difference after any number of miles, either here or there.
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Old 09-16-09, 06:50 PM
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Originally Posted by grolby View Post
On a similar note, anyone who thinks that normal riding doesn't commonly exceed the fatigue limit for a typical lightweight steel or Ti frame is smoking crack. ALL frames accumulate fatigue, and all frames are designed to account for this.
metallurgist?
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Old 09-16-09, 07:03 PM
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Why do we even worry about this. Majority of riders never accumulate enough miles anyway to make any difference what material their frames are made of. From general experience from most riders, you can't kill a steel or Ti frame in normal riding conditions or even in real bad conditions. That's why you see all these old beat up steelies still coming out of the woodwork in eBay ready to take on many more years of punishment .....as FG/SS reincarnations on our Baaad city streets!!
Like someone said in the C&V forum, many steel bikes are like cockroaches. you just can't kill em!
From what we see, Ti frames are super cockroaches!
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Old 09-16-09, 07:29 PM
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Originally Posted by silversx80 View Post
Not quite. I think you're mistaken on what, exactly, the definition of a fatigue/endurance limit actually is. Yes, forces will exceed that limit, on a singular-level (so not exactly to exceed the limit). Impact, for example, isn't as much of a cycle (no pun intended) as pedal forces. The limit refers to the repeated stresses the material can endure before you get fatigue failure (fractures in the material). Once you hit that limit, the material has essentially failed and those cracks will continue to propagate until catastrophic failure.

So, the point is, the higher the stress, the lower number of cycles the material can endure at that stress. If the stress reaches yield strength, you'll have plastic deformation of the material. Fatigue limit is not a singular force/stress capability, but rather a curve relating number of cycles to stress levels.
It's not clear from the above what you think I'm mistaken about. Yes, there is a curve relating the number of cycles that can be sustained before failure vs. the stress level reached in each cycle. The idea of an 'endurance limit' is that that curve becomes asymptotically horizontal at some fairly low stress level - i.e. that below that stress level there can be an infinite number of cycles and the material will still never fail. That could be an important consideration in an application where the stresses can be kept at such a well-controlled and minimal level.

But in normal cycling there will be a wide range of forces - some pretty small such as when pedaling along at an even pace on a smooth surface, but also some that are much higher such as when sprinting, or struggling to make it up a short but steep pitch, or hitting a pothole. When considering such a wide range of stress levels it's impractical to design a frame so that all of the stresses encountered will be so small that they are below the endurance limit (if one even exists for the material as fabricated into a frame) while also keeping the weight at a level that's marketable.
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