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steel vs aluminum...misconceptions misnomers.(12 posts)

steel vs aluminum...misconceptions misnomers.ishmael
Feb 9, 2003 9:17 PM
I was talking to someone who knows about different materials and there characteristics and he said steel and aluminum have about the same life span if both are kept from salt. He also said if you put your carbon frame in the oven at 300 it will turn into CO2..Poof..
re: steel vs aluminum...misconceptions misnomers.Woof the dog
Feb 10, 2003 12:39 AM
bullshit, I don't know the terms, but I know that steel resists repetitive bending a lot better than aluminum, to put it in dog's terms.

No?

Woof
apples and apples?DougSloan
Feb 10, 2003 8:08 AM
How long would a 2 pound steel bike frame last?

How long would a 4 pound aluminum bike frame last?

My money says the 4 pound aluminum frame would outlast the 2 pound steel frame.

We tend to compare heavy steel frames with the lightest aluminum ones. That's probably not a fair comparison in terms of durability.

Doug
apples and apples?MR_GRUMPY
Feb 10, 2003 10:48 AM
A 1Kg aluminum frame and a 1.4Kg steel frame will have about the same life span. 1-2 years max. A 1.4Kg aluminum and a 1.8Kg steel frame will last many many years if they are made correctly.
Yes, steel frames will rust out if you leave them sitting outside for a year or two. Ti frames are a little lighter than steel, but good Ti frames cost big $. It would be interesting to know how well carbon frames take crashing. I would hate to drop a pile of money on a carbon frame, and have it break on my first crash on it.
re: carboncyclopathic
Feb 11, 2003 7:57 AM
carbon has own problems. Epoxy which glues layers eventually fails and bike becomes noodly. Good thing you'd see it way before frame falls apart. The friend of mine dropped OCLV frame for this reason, but he's got it used, built as 30lbs+ audax pig and gotten several years out of it including riding LEL.

Carbon doesn't like crashing I had cracked carbon chainstays crashing mtb on rocks. However it was easy to repair with epoxy and fiberglass or kevlar.
Steel rusts out!micha
Feb 10, 2003 2:40 AM
A few years ago I bought a Murray lawn mower from K-Mart. Its steel deck rusted out on me. The guy across the street has an old Honda lawn mower with an aluminum deck. It looks like new!

In spite of this highly scientific observation, I went out and bought a US-made steel bicycle. I must be dumb. ;-)
I don't think they use Dedacci, Reynolds 853, or Foco for...joekm
Feb 10, 2003 6:17 AM
Murray lawn mowers.

The best thing you can do for steel and aluminum frames to resist corrosion is a good and well maintained coat of paint.
last the same? it really dependscyclopathic
Feb 10, 2003 7:18 AM
on use.

Most Al alloys have very low or none fatigue limit so given even minuscule load it will eventually fail. Steel does have good fatigue endurance, but because frames designed with smaller tubes they flex more. Steel will eventually fail if you exceed limit enough. Second to compete with Al steel is made thinner and thinner and it reduces lifespan.

Third, frame failure is usually associated with manufacturing stress. Welding, drilling, cutting creates stress points and microfractures; this happens to all materials.

Look at the warranties steel frames carry lifetime where most Al don't. Still Al frames designed to last 30-35,000mi it is unlikely casual rider will see frame failure. However there're old school steel frames out there which successfully logged over 100,000mi.

To sum up if you take powerful 200lbs+ guy who doesn't ride many miles but who loves to sprint and races crits yes Al frame may outlast steel. Smaller guy riding lotsa LSD miles would be better off with steel
are we talking theoretical or real?DougSloan
Feb 10, 2003 8:05 AM
In theory, barring rust, and all else equal, steel should last longer.

However, that may mean a well cared-for steel bike would last 100 years, and an aluminum 50 years. In that event, is the difference meaningful? In other words, if they both last "long enough", as a practical matter their life span is the same.

Doug
These debates get nowhere, butOldEdScott
Feb 10, 2003 9:31 AM
haven't I read fairly authoritatively that an aluminum frame under fairly constant use is susceptible to failure in just a few years? Five? Seven? For some reason that's stuck in my head.

I think the advice above -- crit racers/sprinters get aluminum, LSD mileage junkies get steel -- seems pretty fair, given the facts as I think I know them.

Still, I have to admit that, outside of spectacular crashes, especially mountain bike crashes, I've never personally know anyone to suffer frame failure, certainly not JRA frame failure.
Steel can fail.mapei boy
Feb 10, 2003 4:49 PM
I don't know if it can be called frame failure, but one day a couple years ago, my wife noticed that the front wheel seemed kind of loose on her steel-framed, steel-forked mid-eighties Pogliaghi. I checked it out and found that one of the fork tines had given up the ghost with fatigue. I was able to twist the tine off the fork crown with no more than gentle pressure from my hand. There was no rust. The chrome was still good. Though she'd fallen a couple times over the years, she'd never had what could genuinely be called a crash. As for mileage, who knows? She'd ridden it steady for about fifteen years. She was a fairly gentle rider. She only had to change her rims once. All the components were the original ones - except for a Campy SuperRecord seatpost that failed the year before.
does anyone know what they're talking about?ishmael
Feb 10, 2003 5:56 PM
so what would, say, an 853 frame outlast? Steel is touted as the material that lasts, but in a comparison to, say, a frame of the same weight or lighter made of aluminum which would outlast the other given typical use? (assuming both are welded well) And how is this known? Also, the guy I was speaking to said that when either of these materials fail they fail in the same manner. I was told that aluminum will just snap while steel will show signs of cracking before it snaps.