ColonelSanders

I know there is no one "right answer" to the question I am asking, because there are so many variables to take into consideration, including quality of the workmanship and materials used in constructing a frame, but I'm going to give this "how long is a piece of string" question a go anyway.

Let's say the rider is 270 pounds, he rides approx 5,000 miles a year on roads that are okay, with the odd pothole here and there he will encounter.

Would you think it likely that a frame made out of any of the three materials I mentioned in the thread title, would not lasting a decade?

Would they last two decades?

Again assuming the above conditions that I stated would apply, for every year of each decade.

Also assume that each frame comes from a quality manufacturer on a bike that costs about $2,000 retail.

Homebrew01

Maybe

rydabent

Why not include titanium the forever metal?

Retro Grouch 

"Strong, light, cheap. Pick any two."

The issue isn't the material that a bicycle is made out of, it's the design decisions that went into the "strong, light, cheap" triage.

ColonelSanders

Okay, let's say the choice of frame is out of a Specialized Crosstrail Expert with their M4 aluminium or Giant's Toughroad with their SLR aluminium vs something like the Kona Big Rove ST with 4130 steel or Surly's Disck Trucker 4130 steel.

Forget I asked about Carbon.

HillRider

As a very broad generality, steel (or Ti) frames will outlast an aluminum frame since they aren't subject to a finite fatigue life while aluminum is. That said, the fatigue life of a durably built, not ultra light, aluminum frame could be many decades but a steel frame protected from rust damage can be an heirloom.

At your weight don't even think of an ultra light boutique steel (or aluminum) frame. Surly's Disc Trucker should last indefinitely since it's intended to carry the rider and who knows how much luggage weight over long touring distances.

shelbyfv

I don't think it would be a problem for any of the bikes you listed to give good service for 10 years. A bike designed for your weight should hold up, regardless of material. Consider also that if you continue to ride 5000 miles a year, you aren't likely to continue to weigh 270# (unless you are 7 feet tall!) Also, if you stay involved in cycling, 10 years is a long time to go w/o N+1.

Andrew R Stewart 

Far more likely a situation which would limit a bike's life span is the components and the frame's ability to be compatible with those components yet to be conceived or designed yet. An example is the BB shell. When the very standard threaded BBs are no longer available the bikes needed them will be at the end of their useful life. A collector of bikes could give you many more examples of the changing standards and the loss of manufacturing of the old fitting components.

I joke with my customers that if steel as a frame material was "discovered" tomorrow it would be hailed as a wonder material. Widely available in numerous shapes, alloys, dimensions (of tubing), a limitless fatigue life (if designed well), lower mining/smelting/processing/joining costs, stronger, stiffer when compared to AL and in some degrees, carbon and TI. Andy. (who among his 20+ bikes has only 1 AL and a couple with parts of Carbon)

Darth Lefty 

Yes. Or maybe, no? Can't parse. Anyhow, an adequate bike can be made of any of these. 50,000 miles under a heavy rider would be stressful for any of them.

Why not include phlogiston, for all this debate is worth. Nobendium? Corbomite!

Wheever

With a 270 lb rider, crabon asplodes the first time said rider dropes the hamer. Rider must always wear shorts or bib with a Kevlar chamois or risk painful maiming or death.

AnkleWork

Actually, it's a very straightforward calculation if you would just supply those variables. Please include the exact time series of (future) dynamic and static loads and precise CAD models of each frame in question.

dedhed

Big variables would be maintenance and storage as w.ell as riding conditions.Ridden hard put away wet, winter salty roads, indoor climate controlled storage, weekend putter to the farmers market, hard raced weekly. Many variables in the lifespan of a bicycle.

HillRider

Spell check is your (or rather, your reader's) friend. BTW, when did the spelling "asplodes" for explodes become trendy? I've seen it several places.

Kopsis

10 years is not a long time. Any modern frame with a sufficient weight rating should still be serviceable in that time. But at 5000 miles a year, in half that time you'll be looking to upgrade. Get the bike that makes you want to ride and don't worry about longevity. If you manage to wear out any modern non-ultra-light frame, hang it proudly on the wall and get a new one.

Joe Minton

There are a lot of factors that determine frame life. But consider: Steel has ten times the fatigue life of aluminum. Titanium is about the same as steel in this respect. I hear that carbon fiber has a very long fatigue life, however -- it is held together by glue and I'd worry about how long that might last.

Joe

gsa103

From a purely theoretical perspective, a monocoque carbon frame should last the longest. A carbon fiber frame has the same infinite fatigue life as steel and is not prone to rust or corrosion. Lastly the monocoque construction eliminates the weld seams removing a common failure point of other materials.

Erwin8r

Maintenance and care are probably the most important factors, rather than actual frame material, imho.

Joe Minton

gsa103:

Steel does not have an infinite fatigue life unless the stresses are very low. The same is true for Titanium. Aluminum has no lower limit and will eventually fail no matter how low the stresses are.

https://www.asminternational.org/docu...81G_Sample.pdf

https://en.wikipedia.org/wiki/Fatigue_limit

Joe

StanSeven

A good quality frame, intended for other than a lightweight rider, will easily last ten years. That applies to all materials. It also assumes decent maintenance. At 270 lbs, I would be more concerned with wheels, saddle, sestposts, and bars over the same time.

HillRider

The stress below which steel's fatigue life is "infinite" isn't all that low. It's about 50% of the ultimate tensile strength which, for Cr-Mo alloys, is a pretty high stress. In realistic terms, except for frames made with very thin wall tubes where low weight is the major design intent, steel or Ti frames will out live any non-abusive rider by quite a lot.

tcarl

Given the parameters you described above, I'd be more concerned about wheel life than frame life.

oldsmobum

Not trying to be rude or combative, but this isn't accurate. Hopefully sarcasm?

In my experience...
Get whatever you want NEW, and keep an eye on the warranty before you buy. Specialized is lifetime, I think Giant might be too. Then it won't matter as much. Been in the business a long time, and I've seen failures in carbon, Ti, alloy, and steel. Mostly carbon and alloy, but they also comprise the majority of the bikes I encounter around here. I've never in all of my years (fortunately) personally seen a catastrophic (explode) failure from use in any of these materials. Usually you get warning in the form of creaking or excessive flex... Not to say that catastrophic failures never do or never have happened. Now driving into the garage with the bike on the roof, or getting into an accident with a car is another story... I would also suggest steel is the most reliable, but part of this might have to do with the fact that lightness isn't as stressed on steel frames these days for the most part. Carbon has a tendency to crack near the bottom bracket or to come unbonded from metal parts. There are some TIRED old carbon bikes running around still though... Alloy's life can also be impacted by the environment, much like steel it can also corrode in certain environments... Like by the sea. It also has a fatigue life as other's have mentioned. But if you get a quality bike with a good manufacturer's warranty, I wouldn't worry too much.

That being said, I am biased towards steel. Maybe it would be ti if I could afford it, but that would also require a bit more maintenance because it doesn't play nice with dissimilar metals. My two cents.

ColonelSanders

I'm pretty sure that one will be able to get a 68mm BSA for as long as I am alive, plus I'm the kind of guy who is happy to keep spares.

In recent times I have developed a mindset of trying to make my things last as long as is practical, so if I buy something I really like to begin with, I'll be happy with it for some time.

Also I will always have two bikes and as my existing bike is pretty old, it probably could be retired if something so amazing comes out to make my newest bike seem lacking.

For the purpose of the question, assume each bike would be well cared for, no salty roads and ridden moderately hard for those 5,000 miles a year.

I want the warm and fuzzy feelings one gets from having a long owned bike that keeps on keeping.

ColonelSanders

I'm happy to change wheels, saddles, seatposts and the like, I just want to avoid changing my frame.

Happy to change wheels as needed, but want to keep the same frame for as long as I can.

chasm54

As others have said, a steel frame that isn't built to be lightweight could last virtually indefinitely. I volunteered as a mechanic at a bike charity for a couple of years. It wasn't unusual for us to be given bikes that were forty or fifty years old. Aside from crash damage, there was very rarely a problem with the frames beyond a superficial, and trivial, patina of rust. One old guy brought in a Holdsworth that he had bought new in 1952. God knows how many gazillion miles he'd put on it. It was perfect.