Hey all, I've been very curious as to what the advantages are between the two materials. Is SS stronger? Is Ti lighter? Any info?

What application?

Both offer some corrosion resistance (but not elimination) compared to steel and Alu. Both want special joining techniques and skills. SS is actually not as strong as steel is, usually. But both can be used in smart enough ways so this is a minor issue. Ti can be as strong as steel. Ti has a lower density then SS. But since Ti (as well as Alu.) have less stiffness then steel they need to be either made of heavier tubing or larger diameters to have equally still a frame. Both SS and Ti are made in a range of diameters and wall thicknesses. Neither tends to be used as fork blades or steerers.

The real comparison is incomplete without more details known and proper execution. Poor tubing selection or bad joining will be far greater a problem then any inherent differences between these materials. Andy.

Hi,

Steel comes in lots of different strength grades but all grades
are equally stiff, so really good steel allows you to make strong
lightweight flexible frames, cheaper heavier frames are stiffer.

Titanium comes in grades about the same strength as steel,
is about half the density, but is about half as stiff as steel.

However frame stiffness basically depends on tube diameter,
whilst strength is more about wall thickness, but affected
also by tube diameter to a lesser extent.

Basically a titanium frame built with bigger tubes to feel
like a steel frame will end up weighting less than steel.

Same sort of thing with even bigger tubes and thicker
tubes for aluminium alloy frames, as its 3 times less
dense, a 1/3 a strong and a 1/3 as stiff as steel.
Still it makes a lighter bike with bigger/thicker tubing.

rgds, sreten.

"Stainless steel" is a misnomer, it is correctly called "corrosion resistant steel". Some titanium fasteners are offered but they are very costly, not as strong as steel and are subject to embrittlement and fatigue cracking. They are used in aircraft where weight is a prime concern but special design and fastening techniques are needed as well as frequent inspection/replacement. Some so-called "weight weenies" buy them as a weight reduction method but I would not touch them myself.

Titanium is good for fuel lines in fighter jets!

Stainless steel is good for nuts and bolts on boats!

- Joel

there are dozens and dozens of grades of "stainless steel". Some grades (the 300-series is typical) have very high corrosion resistance but lower strength and hardness and cannot be heatreated to improve their strength. Other grades (400-series) have lower corrosion resistance but can be heat treated to very high strength and hardness.

The 300 stainless steels are primarily used for chemical equipment and piping fabrication and 304 is used for most stainless steel spokes. The 400's include the so-called tool steels or cutlery steels and can be used where strength is a major consideration and corrosion resistance is not as important since the environment they are typically used in is not as demanding.

Similarly there are many grades of titanium. CP (chemically pure) Ti is extremely corrosion resistant but has modest strength and only fair fatigue life. It's main use is in chemical equipment manufacture.

Alloy Ti's like 3Al/2.5V (3% aluminum, 2.5% vanadium, balance Ti) or 6Al/4V are much stronger and have great fatigue life but are more difficult to machine and shape. 3Al/2.5V is the Ti alloy most commonly used in bike frame manufacture. A few frames have been made from the stronger 6Al/4V Ti but the consensus seem to be that its extra strength doesn't make up for the difficulty in fabricating it.

AFAIK 6Al4V Ti can only be machined with water jets or lasers.

Those are the way it's done these days since the equipment is available and works better than earlier machine methods. 6Al/4V can be machined with regular metal or carbide tooling but it requires specific cutting lubes and feed rates and is hard on the tooling so, until the water jets and/or laser cutters were available, it wasn't used for many applications.

Thank you all for the info! Much, much appreciated!

A question that was probably already answered (but I'm bad at understanding things) is if I had two bike frames. Both with the same wall thickness, one was SS and one was Ti, which would be lighter and whichwould be stronger?

periodic table: atomic weights: Aluminum 13, Titanium 22, Iron 26.

for a cubic CM of metal that is the relative weight

alloying is normal , none used as elements.

Ti would lighter.....and stronger......depending on the alloys.....and about 10 times harder to work with.....SS is used mostly for corrosion protection,or in the case of bike frames....to give you something to rub on.....

I wouldn't own a stainless frame myself,not that there is anything wrong with them,looks like crap when it's dirty......you could give me a Ti frame and I wouldn't throw it away....but I wouldn't buy one just for riding around.Overkill.

I can't even think of a reason to buy one.....keep up with the Jones' I guess.Well maybe if I was going to ride around on a ships deck while at sea for a couple years......

At the same volume (OD and wall thickness) steel is definitely stronger, and Ti is always lighter since it has a lower specific gravity. Titanium's advantage is that can be stronger for the same weight.

Actually steel remains an excellent material for bike frames. Perversely, the main objection is that it's too strong, so steel tubes have thin walls, and it isn't practical to go the oversize route for stiffness since the walls become too thin (possible to buckle with your thumb).

Good thing you didn't post this to the Frame Builders forum or you would still be dodging flaming errows a year from now. Wow, what a nice box of gross exaggerations of horse sense generalizations.

Ah, you were pulling out legs... right?

Clever, but not terribly useful:
The actual alloys are not pure Al, Ti, and Fe.
Those are atomic, numbers, not weights. The weights are 27, 48, and 56 respectively.
The actual densities of these elements are not easy to extrapolate from either of them: 2.7, 4.5, and 7.9 g/cm.

Besides, actual metal density doesn't correlate directly to atomic weight, since the various metal atoms pack differently. for example Gold has a lower atomic weight than lead, yet is the metal is denser.

Jess if you actually are shopping for a new bike, I'd go with Titanium..

If you are complaining about his comment that all grades of steel are equally stiff, then he is right and you are wrong. The stiffness (Young's modulus) of all grades of steel fall in a very narrow rang as does the modulus for all grades of Ti and all grades of aluminum. Many people can't separate stiffness from strength and they are not the same.