Framebuilders - Material durability

Which frame material is the most durable?

Folks always talk about which is lighter, which is stronger, etc, but which is the most corrosion resistant? Which is the more abrasion resistant?

Titanium? Aluminum? Carbon? Steel?

Which frame material is the most durable?

Folks always talk about which is lighter, which is stronger, etc, but which is the most corrosion resistant? Which is the more abrasion resistant?

Titanium? Aluminum? Carbon? Steel?

For some reason I never thought of abrasion resistance as an important quality in a bicycle. Why do you ask?

Tim

I never really thought about it either, though there was that Ti bike a while back that was worn through a tube by mud/tire action.

I think the problem with this question is:

A) Materials vary less than one might think since builders optimize the strength to some extent. A Ti bike that was made to the same weight as a steel one would be plenty rugged, but not a common animal.

B) Once you introduce 2 or 3 strength measures it isn't going to yield a clear winner. Like Carbon is strong for cycles to failure but not crushing, at least not as commonly made. Composites anyone?

C) It depends how much you want. Like steel is corrosion resistant within the needs of most cycling, but not so good where marine levels of corrosion are concerned. There is likely to be some stuff on a bike that is plain steel anyway, so how much more corrosion resistant than that do you need.

D) How far are you willing to go? If this was a serious milspec kind of test we might find these materials present with coatings far more advanced than what we see in the average bike. What about a hard anodized Al frame or Teflon coated steel. Both these materials get used in military enviros, so they are rugged in the right applications. Ti's price has limited it's widespread adoption, so it is hard to see it purely in structural terms.

My guess is that Ti is the most corrosion and erosion resistant, but it is often paper thin. For every day cycling Al is pretty corrosion resistant, you need something like a penny and some salt water to really get it bubbling. It isn't terribly erosion resistant, but it is the thickest, and fattest to start with. Steel is very good on erosion and not wonderful on corrosion. The later can be improved with coatings, and as mentioned the tubes may not be the weak link.

Steel is very good on erosion and not wonderful on corrosion. The later can be improved with coatings, and as mentioned the tubes may not be the weak link.
Don't forget Reynolds 953 (maraging stainless steel) and Columbus XCr (martensitic stainless steel). Admittedly they're both relatively new and don't have a long track record yet, but both have the corrosion resistance of stainless steel.

It’s not strictly a matter of the material so much as how the material is used. For example, a thin walled frame will see higher stress than a frame with thick tubes. From a corrosion standpoint, the coating process makes a difference. The joining process is critical as well; properly executed welds are critical and I suspect, more durable than bonded joints.

In a general sense I’d say that welded Ti is going to near the top of the durability scale since it has a high fatigue limit and does not corrode in any meaningful way. Steel also has a high fatigue limit but corrosion can be an issue depending on how the frame is treated. Aluminum has no fatigue limit thus it is prone to cracking. Carbon is prone to impact damage, UV aging, bonded joint failure, and other things I’m sure. Not saying carbon is bad, but I couldn’t put it in the same durability class as Ti or steel.

Carbon isnt as impact intolerant as the old myth that gets peddled round still 10 years ago when we were fiddling with thermoplastics in bikes it was tough now its even tougher to the point where bullets wont go through it the problem is that you cant really have your cake and eat it and it doesnt build nice lightweight bikes as peterpan1 states its not something which is cost effective in the bike world

Bonded joints easily match welded joints in many applications the problem is more that people dont know how to bond properly or engineer (if its worth it) a joint properly, in the case of bicycle frames the economics has a large impact on the joint design and often makes it a poor choice in terms of the public slating it receives for failing

mud is an abrasive and no different to any abrasive grinding media due to the fact its a hard particulate suspended in a liquid and even the hardest metals are ground due to it being an effective way to reduce ultra hard materials ,maybe get some wear plates bonded to the area which is being abraded

Carbon isnt as impact intolerant as the old myth that gets peddled round still 10 years ago when we were fiddling with thermoplastics in bikes it was tough now its even tougher to the point where bullets wont go through it the problem is that you cant really have your cake and eat it and it doesnt build nice lightweight bikes as peterpan1 states its not something which is cost effective in the bike world

Bonded joints easily match welded joints in many applications the problem is more that people dont know how to bond properly or engineer (if its worth it) a joint properly, in the case of bicycle frames the economics has a large impact on the joint design and often makes it a poor choice in terms of the public slating it receives for failing

mud is an abrasive and no different to any abrasive grinding media due to the fact its a hard particulate suspended in a liquid and even the hardest metals are ground due to it being an effective way to reduce ultra hard materials ,maybe get some wear plates bonded to the area which is being abraded


Sorry to sound critical but...punctuation improves readability and credibility. Yes, I am a grump. Sorry again.

Don't forget Reynolds 953 (maraging stainless steel) and Columbus XCr (martensitic stainless steel). Admittedly they're both relatively new and don't have a long track record yet, but both have the corrosion resistance of stainless steel.

953 won't have awesome corrosion resistance, certainly not as good as XCR. And neither come close to plain 304 stainless.


Back to topic:

If framebuilding was simply a case of plain numbers, steels would win on all mechanical proerty points. Highest fracture toughness, check. Highest UTS, check. Highest elongation during failure, check. Things like density wouldn't factor for much if money was no object, as the most expensive, strongest, toughest steels hold by far and away the pinnacle of mechanical properties.

But as any builder here will tell you it's not that simple. First and most importantly economics factor. What you can work with for the money. Coupled to that - nt many manufacturers of engineerin g materials draw tube or other bike friendly shapes, and even fewer know how to butt.

Second - as builders here will also point out, builders are experimenters They adjust and experiment with frame materials until they first get somethign that works, then refine it to maximise the benefits inherent in any material and try to ameliorate its inherent weaknesses. As Thylacine will say, there are no bad materials, just bad designs.

My two penn'orth remains steel :-)

Sorry to sound critical but...punctuation improves readability and credability. Yes, I am a grump. Sorry again.


Errm!! (Clears throat) Correct spelling helps too.

:D

For some reason I never thought of abrasion resistance as an important quality in a bicycle. Why do you ask?

Tim

Only because I've heard that abrasion compromises carbon fibre. I have no idea if that's true or not.

I agree that above a certain level abrasion should not be an important quality for a bicycle frame, but does carbon fibre even attain that level?

Errm!! (Clears throat) Correct spelling helps too.

:D

Agree! :o:o:o

953 won't have awesome corrosion resistance, certainly not as good as XCR. And neither come close to plain 304 stainless.
Falanx, is there some way to quantify the relative corrosion resistance of 953 (which, according to the Reynolds website, has corrosion resistance superior to type 410 stainless steels).

I can't find anything on the Columbus website about the composition of XCr, other than "This new stainless steel, developed by Aubert & Duval, the famous French steel mill, was specifically requested by the military industry, looking for a valid substitute for the cadmium plated temper hardening steels which could no longer be produced because of their highly polluting manufacturing process." ed. - Someone should teach the Italians about the use of commas and run-on sentences. :)

Looking at web resources for information on corrosion resistance of stainless steels, 410 is said to combine superior wear resistance of high carbon alloys with the excellent corrosion resistance of chromium stainless steels. Grade 304 is said to have excellent corrosion resistance in a wide range of atmospheric environments and many corrosive media.

There are lots of numbers floated for both 410 and 304, but as a layperson I haven't a clue what they mean, and since Columbus really doesn't say what type stainless is the material used in XCr, I don't know which alloy properties best represent it.

Are there any numbers that would offer some insight into the relative corrosion resistance of these alloys?

Thanks.

Falanx, is there some way to quantify the relative corrosion resistance of 953 (which, according to the Reynolds website, has corrosion resistance superior to type 410 stainless steels).

I can't find anything on the Columbus website about the composition of XCr, other than "This new stainless steel, developed by Aubert & Duval, the famous French steel mill, was specifically requested by the military industry, looking for a valid substitute for the cadmium plated temper hardening steels which could no longer be produced because of their highly polluting manufacturing process." ed. - Someone should teach the Italians about the use of commas and run-on sentences. :)

Looking at web resources for information on corrosion resistance of stainless steels, 410 is said to combine superior wear resistance of high carbon alloys with the excellent corrosion resistance of chromium stainless steels. Grade 304 is said to have excellent corrosion resistance in a wide range of atmospheric environments and many corrosive media.

There are lots of numbers floated for both 410 and 304, but as a layperson I haven't a clue what they mean, and since Columbus really doesn't say what type stainless is the material used in XCr, I don't know which alloy properties best represent it.

Are there any numbers that would offer some insight into the relative corrosion resistance of these alloys?

Thanks.

Right, I'll address these simply, 'cause it's easier than getting into some long winded explanation.

304 - resistance to all oxidising media - that's all the acids that have oxygen in them plus hydrofluoric, all alkalis and anything with a 'per' in it's chemical name. Mildly resistant to reducing media - that's acids without oxygen in them and most ionic binary compounds of same. 18% chromium providesd general corrosion resistance and good resistance to oxidisers, 8-10% nickel content provides resistance to reducing media and keeps the alloy austenitic.

410 - not as resistant to any media as 304. Contains no nickel and is martenistic, so is susceptible to hydrogen embrittlement, too.

953 - Made from an alloy called Carpenter Custom 455. Not as corrosion resistant as 304. In forgings more corrosion resistant than 410. In welded structures no-one knows, but extremely unlikely to be as good as forged. Heat affected zones and variable precipitate density, distribution, dimensions and alterations in chemistry across the HAZ because of precipitation from heat treatment and welding.
Custom 455 was never designed to be welded. It's a forging stock. You*can* weld it, but its chemistry wasn't chosen to be corrosion tolerent to welding.

XCR - 16% Cr, 5% Ni, 1% Mo. Better corrosion resistance than 953 or 410, even welded. That'll be the molybdenum. Columbus do tell you what's in it, kinda. Columbus get the tubing from Trafil, who make Werkestoffe no 1.4418 steel for it.

Actually 304 doesn't have excellent corrosion resistance. It's normally the baseline stainless for chemical contact. Somehow, over the years that message has got a bit misinterpreted.

^ ^ Great! Thanks, Falanx.

My vote goes for Ti.

From my simplistic point of view, Here in South Florida riding along the beach ruins just about everything. Of my many bikes, and my friends bikes, only the Ti frames last. Even then, it must be a heavy duty Ti frame, not an ultra light, super thin version. As you might expect, if built too thin, they will fail too. Unfortunatly, some Ti frames are simply too light. But they do not corrode, and if built well, they do not crack.

I am currently at about 2000 miles on my Ti frame. My last bike, a steel frame made it about 10K miles before it was too far gone. It had corroded and cracked.

From an aerospace point of view, Ti has been the standard for parts that need all the properties you require.



Chris

It's possible for the search for immortality (or indestructibility, or invincibility) to find additional avenues of exploration.

Which frame material is the most durable?

Folks always talk about which is lighter, which is stronger, etc, but which is the most corrosion resistant? Which is the more abrasion resistant?

Titanium? Aluminum? Carbon? Steel?
I've wondered about these things too, quite a bit.

None of them will last forever.

Some will last longer than others, and the 'winners' will be different depending on conditions.

Even diamonds won't last forever.

*****
I have found it liberating to get into another mindset. It is a lot more fun, at times, to test things and see how strong they really are.

You don't have to be in 'preservation mode' interminably. It can be a bit stultifying (or something along those lines) -- and it can be nice to wear another hat once in a while.

*****
[There is something oddly elusive about some of these frame materials questions and inquiries. I think we may not know exactly what it is we are after, or what we are looking for.

Something with the aura of invincibility is nice to be around (for some reason..., at times at least).]

*****
[Death and mortality may be in the background of some of these inquiries and interests.]

From an aerospace point of view, Ti has been the standard for parts that need all the properties you require.

Chris

Except in main landing gear, gearboxes, slat controls, pumps, impellers, rotors, shafts, skins, bay doors, stringers, longerons, steering knuckles, missile bodies, missile control surfaces, coolant and oil lines and three quarters of turbine assemblies, yes.

Sorry. Aerospace engineer ;-)

I'm not an engineer of any stripe, but I do have a bit of experience with bicycles. Based upon personal observation, I'd say that I've seen more broken aluminum frames than anything else, followed by carbon, steel, and titanium. And I've never seen a titanium frame rust into uselessness, either.

Realistically, a properly cared-for steel frame should last most of a lifetime. A titanium frame will probably go at least that long, with less care. Carbon bicycle frames haven't been around long enough for us to know for sure. And aluminum frames are more susceptible to joint failure than any others, as far as I can tell, which is not to say that they can't last a very long time, but that the odds are worse than for other materials.

HTH!

Which frame material is the most durable?

Folks always talk about which is lighter, which is stronger, etc, but which is the most corrosion resistant? Which is the more abrasion resistant?

Titanium? Aluminum? Carbon? Steel?

I thought about this some more, and the simple and straightforward answer -- to which is the most durable (for real-world bikes, under most real-world conditions) -- is almost certainly some of the exotic steels.

If you look at the numbers, it is striking. They are not only harder, they are much harder. The yield strengths are not only higher, they are much higher.

They are much tougher as well, and have other superior characteristics.

The numbers are available on the web. It can help to see them for yourself, and compare them. It brings the facts home.

Titanium has a certain sort of name-recognition and aura and reputation; but the facts speak differently.

953 and some of the other steels just blow it away, by these various measures.

Some of the steels can benefit from corrosion protection, if exposed to certain conditions; but that can be arranged without too much trouble.

*****
That said, with a reasonable level of care, a good Ti bike can also last several lifetimes.

So could carbon and aluminum; but they are (relatively speaking) more subject to various sorts of damage and failure.

*****
Scratches and abrasion resistance: the harder exotic steels win.

*****
If you tried using these different materials against one another in a sort of swordfight, to see which ones would destroy which, the tougher and harder exotic steels would win.

If you threw rocks at them, carbon would probably go first, followed by aluminum.

I've heard that titanium can develop weak spots from strong, sharp impacts; but I've never seen this confirmed.

*****
Corrosion resistance: it would have to depend on conditions -- just water? Heavy salt(s)? What?

Unprotected?

Well-protected steels will last a very, very long time -- lifetimes. Even in wet conditions. Some of the stainless steels will hold up even better.

Except in main landing gear, gearboxes, slat controls, pumps, impellers, rotors, shafts, skins, bay doors, stringers, longerons, steering knuckles, missile bodies, missile control surfaces, coolant and oil lines and three quarters of turbine assemblies, yes.

Sorry. Aerospace engineer ;-)

Main landing gear of heavy jets are steel, they would be too big if made of anything else. Gearboxes contain steel gears. Slat controls may or may not contain Ti. Falcon jet slats have extensive use of Ti. Pumps are steel and aluminum. As are wear nearly all wear parts. Rotors (compressor disc and blades) are Ti on our G550, As are the impellers on the Turbomecca compressors on our heli. Also Ti are non wearing shafts in the flight control systems. Skins are Aluminum as are doors and stringers (also carbon fiber) Steering nuckles (in our case, bellcranks) are Ti on the Gulfstream. Could not say with regard to missles. Fluid lines are all stainless and turbine assys are high nickel alloy. Also, Ti is used on both our helicopter and Gulfstream firewalls.

Quite a good mix of materials. Obviously, aerospace engineers use the proper material for the job at hand. Which really is the original question. Too bad I answered in such a simple manner.

I think if you put the question in aerospace terms, Ti is used where long life is needed, corrosion resistance is important, thermal stability is important, weight is important, and cost is not the overriding factor. One area where Ti does not do well is any surface that has high wear or friction related issues. So the above example of gears, pumps, landing gear, and the like are clearly the realm of steel.

But, I stand by my statement. The best bicycle frame material, IMHO is Ti. It does not need paint or corrosion protection of any type, it is strong, very resistant to fatigue failure, light, weldable, repairable, machinable, commonly available, it looks good when polished and remains polished nearly forever. It is as close to a lifetime bicycle frame material as I have ever seen. Remember that stainless does corrode. One look at any boat in salt water will prove that point.

My Ti seat post will never get stuck in my Ti frame, ever. Nor will the bottom bracket threads corrode, ever.

I am willing to see the error of my ways. Please let me know the down side.

Chris

...Lotsa knowledge....
Chris

So you are a fellow plane mech! Yay! Found one!

Not all planes are made like the Gulfstreams or choppers though. And you'll have to excuse any confusion between our terms, being as you're one side of the pond and I'm the other. Not everything means quite the same...

The MLG of all planes are steel. Not just the big'uns. 300M, D6AC, Hy-Tuff or Carpenter Custom 465.
The slat control gears themselves? Or the slat stanchions/tracks/pistons?
Compressor discs, blades, blisks and blings are usually Ti alloys these days yes, but chopper rotors aren't. And most of the jet engine parts in Ti are in development to become SiC fibre reinforced Ti-alloy composites.
Bellcranks are Ti on the Gulfstream, too? I shall remember that ;-)
For reference, missiles are *always* steel bodies. You can't make a thin-walled tube take a 40g hard turn at Mach 3+ if it's anything but.

How many boat parts made of stainless steel have you seen? There aren't that many I can think of and all of those aren't really stainless steels - they're what get referred to as corrosion resistant alloys. If it doesn't contain 18% chromium, you're kidding yourself that it's stainless steel. The problem with salt water as a corrosion medium for steels is the chloride ion. While chromium-bearing steels are very resistant to oxidising media, they fair not so well in reducing media, of which the chloride ion numbers. Having said that, titanium is also attacked by Cl-. That's why proper stainless steels have over 8% nickel in them too, and preferably some nitrogen and molybdenum.

I'll refer you to one of the framebuilders around here who makes no secret of his preference for Ti, and I can see his point. When it comes to environmental resistance per unit cost, despite the shocking rise in commodity prices, Ti still delivers most.

It even performs just over half as well as steel in mechanical tests. If money were no object, then I can recommend only one material. I could even design it for you, right down to the heat-treatment procedure and precipitation sequence. It would be steel.

But you'd have to be very rich.

... It does not need paint or corrosion protection of any type, it is strong, very resistant to fatigue failure, light, weldable, repairable, machinable, commonly available, it looks good when polished and remains polished nearly forever. It is as close to a lifetime bicycle frame material as I have ever seen. Remember that stainless does corrode. One look at any boat in salt water will prove that point.

My Ti seat post will never get stuck in my Ti frame, ever. Nor will the bottom bracket threads corrode, ever.

Titanium is an excellent material; but I am not at all convinced that it trumps some of the finer steels.;)

Many cyclists do not have to deal with much salt at all; it varies, but many just don't have that problem to deal with, in reality.

There are ways of protecting steel.

Stainless steels differ widely. Some of them are much more corrosion resistant than others.

Titanium can and does fuse with some other materials.

Its fatigue life in some tests is unexceptional.

*****
"...Remember that stainless does corrode. One look at any boat in salt water will prove that point."

This seems like one of those hypothetical examples that are not closely related to bike frames in the real world. How many bike frames sit in salt water like a boat? (What about the chain, bottom bracket, bearings, cogs, etc.?)

If that is actually one's application, then an appropriate material for that situation is in order. Otherwise, it seems not to be very applicable. It certainly is not very applicable for many cyclists, in their actual conditions.

There is sufficient corrosion resistance in real-world conditions, for many people, in some of the steels.

*****
One can imagine various sorts of situations (some of them a bit fanciful) -- and different materials will come out ahead depending on the nature of the stresses and environments.

For most bike frames, in the real world, it seems to me that some of the steels are at least the equal of the titanium alloys.

*****
One could make a long list of materials' characteristics, and various possible sources of damage, and then rate each material and alloy for each set of conditions.

(Carbon fiber would blow away the rest of the field in at least of couple of those.)

One could then rate each one of these potential sources of damage -- rate each one for likelihood (for an individual's actual uses), duration, etc., and assign a weight to the importance of each attribute.... and tailor it to the individual and his or her needs, preferences, etc.

For most people, it seems to me that some of the steels (especially the stainless steels) would be at least the equal of the titaniums.

I agree that it is a close call in some ways, and that each material can look like the best, if one focuses on its strong points; but overall -- taking all of the factors into account, not focusing on just some of them, and taking actual real-world riding and real-world conditions and the individual into account -- if I could have any of the available materials in the bike of my dreams, it would probably be one of these corrosion-resistant steels.

[Though I have to admit that the fact that scratches in brushed titanium can be easily rubbed out (as described on Habanero's site) compensates for ti's much-worse performance in that category (scratch resistance), compared with some of the hardened steels. That is a real factor for me.

There are other factors, though, that weigh more in the steels' favor.

It's close in some ways, though....]

Light scratches in titanium may be fairly easy to rub out; what Habanero doesn't mention (and I don't blame them, really -- they are selling ti] is that not all scratches are of this nature, and not all of them are equally easy to deal with.

Deeper gouges, like those mentioned here,

http://www.bikeforums.net/showthread.php?t=381939

are not so easy.

*****
This makes me lean more toward the far more scratch-, abrasion-, and gouge-resistant materials that are available.

This makes me lean more toward the far more scratch-, abrasion-, and gouge-resistant materials that are available.

Lemme guess, they start with iron and end with a complex precipitation sequence? ;-)

No question steel and it's various alloys can be fantastic. However, every steel bike I have ever owned, has not been a "lifetime" bike. My sweat corrodes the steel, often right through the paint. I have never been able to stop the internal corrosion, even with access to some of the very best CIC compounds. Once the rust starts, it is nearly impossible to stop. All it takes in an unseen internal spot.

Riding in the rain is also a factor. Road splash contains all sorts of corrosive stuff. Salt may be one of them, depending on where you live. Snow in winter? Maybe your area has salt on the roads.

I have never seen a stainless bike that was worth looking at. Even 18-8 CRES corrodes. When it does, a crack develops. Nor are most CRES components anywhere near as fatigue tolerant.

Here in Florida, the CRES (stainless) v-band clamps used to hold aircraft generators/fuel control units/starters/hydraulic pumps and the like are prone to cracking. Right at a TINY corrosion spot, every time.

Ti, on the other hand, makes fantastic springs. Motocross bikes use Ti springs on the rear shock. In this application, they retain desirable properties much longer than spring steel, while being lighter. Just how much more fatigue resistant does this material need to be?

Allow me to back this discussion to the original post and my interpretation of it. I have never seen a commonly available bike frame material that exceeds the excellent properties of Ti.

Sure, some magic steel alloy that is corrosion proof, fatigue proof, stiff, strong, light, abrasion resistant, and somewhat affordable may exist. I don't know of it. Otherwise, in my use steel rusts, and it cannot be stopped.

Chris

I have never seen a stainless bike that was worth looking at. Even 18-8 CRES corrodes. When it does, a crack develops. Nor are most CRES components anywhere near as fatigue tolerant.



I'll return to the statement I made a few posts back about 304-type stainless steel having poor corrosion resistance. Especially unpassivated.



Here in Florida, the CRES (stainless) v-band clamps used to hold aircraft generators/fuel control units/starters/hydraulic pumps and the like are prone to cracking. Right at a TINY corrosion spot, every time.


Again, 304-type. And if they are, that supplier should be canned. ALL stainless steels used in aircraft are required to be properly passivated. MIL-STDs.


...Ti, on the other hand, makes fantastic springs. Motocross bikes use Ti springs on the rear shock. In this application, they retain desirable properties much longer than spring steel...


Sorry mate, but that's rubbish. Are you saying that spring steels temper at room temperature, or on a hot day?


Sure, some magic steel alloy that is corrosion proof, fatigue proof, stiff, strong, light, abrasion resistant, and somewhat affordable may exist. I don't know of it. Otherwise, in my use steel rusts, and it cannot be stopped.


Corrosion proof? Find one with a PREN over 29. Check.

Fatigue-proof? ALL ARE. I think you mean that austenitics have a lower fatigue limit than 6/4 Ti alloy. You have to be careful when you say things like that.

Stiff? Check. Stiffer than any other material used in frames. See above.

Strong? Check. See above.

Light? Do you mean low density? If you mean the highest strength-to-density-ratio of any material used in frames, then yes. Check. See above...

Abrasion resistant? Check. Superior tribological properties to any other material used in frames.

Somewhat Affordable? That's a decision caused by market forces. You'd never have heard of stainless maraging steels in this application if Reynolds hadn't tried it. How much does it cost you to buy a 953 tubeset to build? 250 quid. How much woul dit cost you, Chris, to have that tube drawn yourself? Base cost of the alloy is lower than base cost of 6/4. End of. It's just expensive because the minimum order is 5000lbs and you don't need that much.

I live in the UK. Which is, I guarantee you, wetter per se than anywhere in mainland USA. We can see rust happening and have plenty of time to go for a cuppa, nip to the chippy come back and stop it. Why can't you guys?



This whole thread is getting a bit Fan-Boi for my liking, and I have to apologise if I've incited it. We're in danger of veering off down the hypotheticals route. As it presently stands there are two major poles - steel and titanium. I think we can leave it at that before it starts getting rude.

Well, I am not a fan boy of any particular brand. I simply have a few miles and years of experience. I gave my honest opinion based on my experience. That is all it is, an opinion.

It is, of course, OK if you disagree. We each have our reasons for our opinions.

BTW, some current motocross bikes use Ti rear springs. The reason is for weight savings. Other than the fact that I am an ex "A" level rider and I know that steel springs last about 1 season max before loosing some strength. Generally noticed quite early on by increased rear sag dimensions. My point was simply that Ti is good enough to outperform the typical steel spring in this application, while weighing less. Don't read into what I said.

I thought I was careful when I said "I don't know of it. Otherwise, in my use steel rusts, and it cannot be stopped."

Obviously, I have found something that works for me. All I wanted to do was share this info. Sorry for not being able to make my case.

Chris

I wasn't trying to make things personal... never mind.

What you're saying still doesn't make any sense, though. If you're using titanium as a replacement for steel to save weight, then the component still has to perform the same as the steel one. Titanium only has half the Young modulus of an equal volume of steel but two thirds its density. That's why they use steel in Main Landing Gear *because* it weights MORE to do the SAME job.

A spring is a component that is Young modulus limited. The spring rate and rebound of a spring is not a strength limited issue, it is stiffness, and as I've already said, Ti is only ~50% the stiffness of steel but 65% it's density. Unless you are designing a Ti spring to ALSO have a lower loading limit then what you're saying is patently wrong.

Now, are you using layman's 'sag' and therefore deflection, or engineers 'sag' and therefore permanent set? I'm sorry, but either way there's still something wrong there.
If the spring has permanently deformed because it's been overloaded, and therefore is now shorter, then you've got either badly designed or incorrectly heat-treated springs, nothing more. What you're reporting is a manufacturing issue. It's been either shaped wrong and it's helix is too open, or it's got sh*tty heat-treatment. Or Motocross bikes somehow warp physics in their locale...
If you are claiming that the action of using a spring lowers its Young modulus, then Whiskey Tango Foxtrot, over?
A material undergoing fatigue would be getting stronger, not weaker and less stiff. Fatigue is a plastic working phenomenon. It gets stronger right up until it breaks. That's not exactly sag.


What I'm trying to get at Chris, is that what you have found is not representative of most situations or real-world examples. Some of what you've posted just doesn't fit with materials science. I'm not a fan-boy either, but my posts are based on not just what I have found, but what materials engineers the world over have found, hundreds and hundreds of times over.




I'm all for people handing out their experiences so that others can learn from them, but the problem with offering opinions that don't match the science is that the result is the Old Wives Tales that the medical profession had to spend more than two hundred years fighting.

"I live in the UK. Which is, I guarantee you, wetter per se than anywhere in mainland USA. We can see rust happening and have plenty of time to go for a cuppa, nip to the chippy come back and stop it. Why can't you guys?"

That's like saying why can't the brits bear up under a trivial snow or heat load, when people here in southern Ontario get more of both. I remember living in Ireland and going rock climbing in the rain all the time. Local mags would have the odd picture of folks friction climbing in small "rivers". If you didn't climb when it rained, you hardly climbed at all. When I came back here, I got criticised for the "insanity" of carrying on when it started to rain, and our local crags are pretty overhanging. Just what the locals are used to I guess.

I would like an option that did not require me to paint at all. That would get interesting even if the tubes were a lot more expensive.

Falanx and all,

Nothing personal here in any way. I want to understand what you say. I have a fantastic ability to use the wrong terms for a particular description. I understand that. A personal problem of mine, not yours. This is one reason why I work alone. I cannot blurt out a coherent thought under stress. Don't worry about offending me. It won't happen.

Anyway, you said: "A material undergoing fatigue would be getting stronger, not weaker and less stiff. Fatigue is a plastic working phenomenon. It gets stronger right up until it breaks. That's not exactly sag."

Did I use the wrong term? Fatigue in this case would be simple use? Or would my example just simply be called use? For example: Valve springs don't get stronger with age. That is why I test them. After 20 years in aircraft use, they get much weaker. The new replacements have new dimensions and "to spec" strength. Same with race car engines and related valve springs. Same with steel dirt bike shock springs. Heck, even my car sits lower now, as do most old cars. They simply weaken over time and use. Manufacturing issue? Maybe. Common? Yes.

Dirt bikes are set up with a "sag" dimension, typically (let's say) 100mm with rider aboard. That dimension will change to 105mm within about 5 races. It will continue the trend. After about 1 year, the pro riders would know that the spring rate was insufficient. Even if the preload was set to the proper 100mm. I used the term fatigue. Probably incorrectly.

How this relates to bicycle use, I don't know. My steel frames, some quite expensive French and Italian versions have all failed. Mostly due to corrosion. My last Trek 4130 steel mountain bike also cracked, in addition to unrelated internal corrosion. Sure it had 10,000 miles on it. Plenty of water made it inside the frame.

Florida is wet, no need to get in that contest. I have heart, kidney, thyroid and other physical issues now. I have found that bicycling is an excellent way to keep me off diuretics and beta blockers. I ride a set schedule, rain or shine. I have to. I ride more than most people and I put on more miles than most. I take no breaks during the year. 10,000 miles is a common lifespan for one of my bikes. I think I am in a good position to point out what works for me! Old wives tale? I think not.

Just in case you were wondering, I have ridden 2 carbon bikes to failure. I do not use carbon fiber any longer. The bottom brackets keep cracking. The carbon forks crack in my use too. I am not smart enough to pick a carbon bike that will last. I am sure it exists. I have not owned it.

Chris

Different strokes for different folks, I guess.

I've owned lots of steel bikes and never had serious corrosion problems with any of them. Last year, though, I decided I wanted a special "lifetime" bike (not that I have a lot of years left in my lifetime :D), and had a custom steel frame built by Waterford using Reynolds 953 stainless. I'm delighted with my new very light, ultra high strength, corrosion resistant bike and intend to ride it into the sunset.

I'm sure that others are just as happy with their titanium bikes.

http://i32.photobucket.com/albums/d7/k4drd/Bicycles/Waterford%20B07014/CIMG4079medcr.jpg

Different strokes for different folks, I guess.

I've owned lots of steel bikes and never had serious corrosion problems with any of them. Last year, though, I decided I wanted a special "lifetime" bike (not that I have a lot of years left in my lifetime :D), and had a custom steel frame built by Waterford using Reynolds 953 stainless. I'm delighted with my new very light, ultra high strength, corrosion resistant bike and intend to ride it into the sunset.

I'm sure that others are just as happy with their titanium bikes.

http://i32.photobucket.com/albums/d7/k4drd/Bicycles/Waterford%20B07014/CIMG4079medcr.jpg

Maybe someday for me as well, but I'm 67, that's a beautiful bike Scooper.

Maybe someday for me as well, but I'm 67, that's a beautiful bike Scooper.
Thanks, George. You're only two years older than I (I'll be 66 in June). :p

That bike is stunnning! Very nice indeed.

Chris

Carbon fiber has certain characteristics that put it at the top of the list -- at least for these specific characteristics (and not necessarily overall), when compared to a wide variety of other materials.

I've seen some tests and data that confirm this.

However, these tests and data did *not* include the very strongest of the steels, so I don't know how these compare.

In one test, handlebars made from a variety of materials [different aluminum alloys and titanium alloys, carbon fiber, and a variety of steels (including some of the stronger hardened steels, but not including the very strongest ones)] were used. The bars were subjected to repeated stress cycles on a machine that simulated the stress cycles that often occur during cross country mountain bike racing.

The aluminums failed first, followed by some of the steels, followed considerably later by the titaniums and other steels. Carbon outlasted all of them.

I don't know how 953 and some of the other ultra-strong steels would compare with 853 in these tests; but some of them would almost certainly last considerably longer.

How they would compare with carbon fiber in these tests, I don't know.

However, carbon fiber, as a frame material (or as a fork or handlebar material) is subject to damage and failures that drop it from the list of most durable materials.

In other types of tests it is not as impressive.

*******
The aesthetics of titanium vs stainless steel are partly personal preference. In the high-polish versions, I prefer stainless. In the satin finishes I have seen, I also prefer stainless. In the brushed versions, I would call it a tie.

Lugs are also a factor, both in terms of aesthetics and in terms of repairability (which can be considered to be an aspect of the durability or longevity of the frame as a whole).

Carbon fiber has certain characteristics that put it at the top of the list -- at least for those specific characteristics (and not necessarily overall), when compared to a wide variety of other materials.

There are some tests and data that confirm this.

However, these tests and data did *not* include the very strongest of the steels, so I don't know how these compare.

In one test, handlebars made from a variety of materials [different aluminum alloys and titanium alloys, carbon fiber, and a variety of steels (including some of the stronger hardened steels, but not including the very strongest ones)] were used. The bars were subjected to repeated stress cycles on a machine that simulated the stress cycles that often occur during cross country mountain bike racing.

The aluminums failed first, followed by some of the steels, followed considerably later by the titaniums and other steels. Carbon outlasted all of them.

I don't know how 953 and some of the other ultra-strong steels would compare with 853 in these tests; but some of them would almost certainly last considerably longer.

How they would compare with carbon fiber in these tests, I don't know.

However, carbon fiber, as a frame material (or as a fork or handlebar material) is subject to damage and failures that drop it from the list of most durable materials.

In other types of tests it is not as impressive.

*******
The aesthetics of titanium vs stainless steel are partly personal preference. In the high-polish versions, I prefer stainless. In the satin finishes I have seen, I also prefer stainless. In the brushed versions, I would call it a tie.

Lugs are also a factor, both in terms of aesthetics and in terms of repairability (which can be considered to be an aspect of the durability or longevity of the frame as a whole).