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Differences between steel and aluminum frames

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Differences between steel and aluminum frames

Old 03-07-12, 06:08 PM
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bikenh
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Differences between steel and aluminum frames

What are they? I realize steel is heavier...I believe it is also cheaper, may...anymore in this day and age not as readily available, at least not from the mainstream manufacturers. When it comes to performance what are the other differences. I've heard them but have never really seen them written anywhere that I can look at them and digest them thoroughly. I'm in the process right now of getting a new bike, since my current frame is pretty much toast. I know I don't have the money for titanium or carbon fiber so I'm trying to decided between steel and aluminum. I've had a Cannondale frame for 20 years so I've haven't really known anything but aluminum. Hence why I'm wondering the differences between the two of them.
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Old 03-07-12, 06:19 PM
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Steel is an alloy of Fe iron 26 and carbon 6, + trace other elements if desired..

aluminum 13 is another element, alloyed to different recipes..

Examples,
in steel 4130 is a specific steel mix, in aluminum 7075 is also a precise description ..

there are specially drawn and heat-treated, high strength steels, that cost more to buy,
just the tube-set.

than a whole wally-world bike.

go to a proper bike shop and they will begin the demystification.

Last edited by fietsbob; 03-07-12 at 10:56 PM.
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Old 03-07-12, 06:27 PM
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Both are good in a used bike the general quality and condition matter more than the frame material.
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Old 03-07-12, 06:28 PM
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Alum tends to be stiffer ,faster and hard on your frame at the end of the day.
Steel flexs more so better for long rides. Custom steel is everywhere, most seem to do wonderful work and charge accordingly, you will have a U.S.A. made bike.
Steel has come a long ways from the boat anchors they sell at wallmart.

Last edited by Rx Rider; 03-08-12 at 04:24 PM. Reason: sure
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Old 03-07-12, 06:33 PM
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Actually an aluminum structure, Has to be stiffer to last, so the designers
see to that in the design engineering of the frameset..
the fat thinwall tubes were a design choice to best use the Al,
due to the mechanical properties of that material ..
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Old 03-07-12, 07:00 PM
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I don't think one can say definitively that aluminum tends to be faster. The difference in a high quality frame would be miniscule compared to so many other factors.
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Old 03-07-12, 07:06 PM
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Welded aluminum frames are now cheaper to make on a mass scale than welded steel frames. This became true only a few years ago. And I believe welding lends itself to automation better than brazing does. I believe most mass-produced brazed frames required individual attention.
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Old 03-07-12, 07:09 PM
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Low end bikes of either metal can run near to 40 lbs.
It's the quality of the metal more than the metal itself that matters.
Better quality (stronger) metal can be drawn thinner.
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Old 03-07-12, 07:25 PM
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Originally Posted by noglider View Post
Welded aluminum frames are now cheaper to make on a mass scale than welded steel frames. This became true only a few years ago. And I believe welding lends itself to automation better than brazing does. I believe most mass-produced brazed frames required individual attention.
+1 pluss for nice lugging or welding realy nicealy welded chromo frames take a tone of work.
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Old 03-07-12, 07:51 PM
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steel is real

This could get to be a heated discussion. I prefer steel. My steel frames weighs 4.2lbs and was reasonably priced at $450. Alluminum is very stiff so it has no give, none. So rather than it flexing, it will break. Now thats not to say that an alluminum frame is going to break just that it will break before it flexes. Alluminum also, because it is so stiff, tends to vibrate. It can and does actually develop a hum. Some people such as myself are sensitive to this. I can feel it in my teeth. There is also the off chance you could be biking across outer mongolia and run into an ox and break your frame. There is someone everywhere that can repair steel not so with alluminum. The biggest difference is ride quality. Go ride a salsa casseroll you will believe in the feel of steel. Plus you get to use all the ryhmes.
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Old 03-07-12, 08:13 PM
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shouldn't be considered good, bad or ugly.
My alum bikes are my race bikes, they are fast because they are stiff, they also make me walk funny after 100 miles.
My steel bike is comfortable and cafe free after 100 miles but not as fast, it just isn't.
If you're on a budget alum is the way to go, a frame should last as long as you need it.
The question that's hard to answer is the choice between steel and CF. they'll both cost the same for a decent version, both give equal rides but if CF really explodes after X years custom steel starts looking better.
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Old 03-07-12, 08:24 PM
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bikenh, There is so much prejudice and hearsay concerning frame material it becomes difficult to find some 'facts'. First is that not all steel tubing is the same, which makes steel a generic name, the same for aluminum. I love my aluminum bikes, but there are some nice frames these days made from R853 tubing. If money is a consideration then one of the Chinese carbon frames on e-bay are a good alternative from the reviews I've read.

Brad
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Old 03-07-12, 08:51 PM
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the specific modulus (stiffness per unit of mass) of titanium, steel and aluminum is almost the same, so the frame designer has much more effect over the performance of the frame than the material
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Old 03-07-12, 08:57 PM
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Originally Posted by Bill Kapaun View Post
Low end bikes of either metal can run near to 40 lbs.
It's the quality of the metal more than the metal itself that matters.
Better quality (stronger) metal can be drawn thinner.
i think you hit the nail on the head
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Old 03-07-12, 09:05 PM
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Good quality vs. crap is 1000 times more important than steel vs. aluminum.

For those that say aluminum gives a harsh ride I rode my '89 Trek 1500 on a 180 mile group ride across Wisconsin (in one day) and was comfortable the entire time. The frame was all aluminum and even the fork was aluminum. Tire width and pressure has a much greater effect on ride quality than frame material.

Originally Posted by bradtx View Post
bikenh, There is so much prejudice and hearsay concerning frame material it becomes difficult to find some 'facts'.
Agreed.
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Old 03-07-12, 10:42 PM
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I really like the feel/responsiveness etc. of CroMo!
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Old 03-07-12, 10:57 PM
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Cure is Shopping .. go ride bikes in the shops, this weekend.
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Old 03-07-12, 11:01 PM
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i hope the OP is taking all this down...
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Old 03-07-12, 11:05 PM
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I can get away with 700x25 or 700x28 tires on a steel road frame.

If I try that on a Cannondale (I have one), it tries to shove the
seat up my ass.

As others have stated, there are significant design differences
in the tubing and the frame use of it between the two materials
that attempt to use the different Young's moduli to best advantage.

Also, aluminum makes much better beer cans, hence the term
"beer can bikes" you see often used on the C+V.

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Old 03-08-12, 06:48 AM
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About half most higher end bikes steal or Aluminium or orther wise have rated rated reynolds frames set tubes ranging from 3 to 8 in grade with most better set sets as 5 somethings or better.
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Old 03-08-12, 07:36 AM
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Aluminum is actually a softer, more flexible material than steel. If you look at the tube diameters of the two materials, however, you'll notice they are not the same thickness. To create a durable aluminum frame, the tubing thickness and diameter must be thicker and larger, respectively, than a comparable steel frame. Thus, steel frames are more forgiving than aluminum.
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Old 03-08-12, 08:08 AM
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Originally Posted by digger531 View Post
This could get to be a heated discussion. I prefer steel. My steel frames weighs 4.2lbs and was reasonably priced at $450. Alluminum is very stiff so it has no give, none. So rather than it flexing, it will break. Now thats not to say that an alluminum frame is going to break just that it will break before it flexes. Alluminum also, because it is so stiff, tends to vibrate. It can and does actually develop a hum. Some people such as myself are sensitive to this. I can feel it in my teeth. There is also the off chance you could be biking across outer mongolia and run into an ox and break your frame. There is someone everywhere that can repair steel not so with alluminum. The biggest difference is ride quality. Go ride a salsa casseroll you will believe in the feel of steel. Plus you get to use all the ryhmes.
So much, so wrong.

Steel is about 3 times the density of aluminum. So an aluminum bike built using the same volume of material as a steel frame would weigh 3 times less. For your example, that would make your 4.2 lb frame a 1.4 lb frame.

But aluminum isn't stiff at all. It's actually about 3 times less stiff then steel. It's also about 3 times less strong. Because it's not stiff nor strong, it can't be built using the same volume of as a steel frame and thus more material has to be used to make the frame. An aluminum frame of comparable strength to your steel frame would need more material which would drive the frame weight closer to 3 lbs. By a trick of geometry that is similar to what is used for I-beams, you can make tubes of aluminum stronger by increasing their diameter. That's where the stiffness of an aluminum frame comes from. You can make the tube thinner and able to withstand the forces necessary for a bike frame and end up with a frame that isn't a noodle. You could do the same with steel but you'd have a bike so stiff it wouldn't be comfortable.

Aluminum does flex. It just has limits on how much it can flex. Aluminum also doesn't vibrate all that well. Because it's not very stiff as a material, it doesn't propagate vibrations as well as steel does. Think of a tuning fork. A steel on will vibrate for a very long time. An aluminum one is rather 'dead', i.e. it doesn't vibrate. Aluminum bikes don't vibrate as well as a steel bike of similar dimensions. The issue is the differences in dimension. As above, if you made a steel bike the same as an aluminum bike it would vibrate like...well...a tuning fork. On the other hand, unless you are riding steel wheels, any road vibration that reaches the rider is being transmitted through the tires (which deaden the vibration), aluminum rims and aluminum hubs. Why don't their vibrational qualities bother you?

Finally there's the repair issue. You can go look around for a Bike Forum member's actual experience with trying to get a damage frame repaired in far off lands...China, actually...on the touring forums. Modern steel frames...and by modern I mean anything made since around 1975...are thin metal frames that require specialized skill to repair. Some guy with a welder in Outer Mongolia will be far more likely to burn through the material than repair it...which is exactly the experience that the poster on the touring forums ran across.
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Old 03-08-12, 08:51 AM
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cyccommute, I've 'defended' aluminum frames for over twenty years using the same argument you've presented with little success. I'd never thought of using a tuning fork as an example, just brilliant.

Brad
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Old 03-08-12, 09:46 AM
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Originally Posted by digger531 View Post
Alluminum is very stiff so it has no give, none. So rather than it flexing, it will break. Now thats not to say that an alluminum frame is going to break just that it will break before it flexes. Alluminum also, because it is so stiff.......
An absolutely fictional, full-of-hogwash post, presented as fact.
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Old 03-08-12, 09:52 AM
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cyccommute and well biked - thank you for replying to that so I didn't have to. +1 and +1.
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