All The Ti Info You Ever Wanted

Article courtesy of Airborne Bicycles customer email list.

Titanium was discovered in 1791 in the mineral menachanite by the British clergyman William Gregor, who named the new element menachite. Four years later, the German chemist Martin Heinrich Klaproth rediscovered the element in the mineral rutile and named it titanium in allusion to the strength of the mythological Greek Titans. The metal was isolated in 1910.

The majority of the titanium tubing used today in the manufacture of high quality bicycle frames is the Ti-3%Al-2.5%V alloy, also known as Ti 3-2.5 or grade 9 (ASTM B338 Grade 9). Because of its excellent combination of strength and ductility, this alloy was created for use as hydraulic lines in high performance aircraft.

Tubing Condition
Ti 3-2.5 comes in two strength conditions, Cold Worked and Stress Relieved (CWSR) and full annealed. The CWSR tubing (as used by Airborne) is the preferred condition for the structural members of the frame due to its higher strength. Although some inexpensive titanium frames are made from annealed tubing, it is not commonly used in high quality frames.

3Al-2.5V vs. 6Al-4V
6Al-4V is comprised of titanium alloyed with 6% aluminum and 4% Vanadium. There are a lot of claims made about the strength of 6/4, but most of it is based on "textbook" numbers for sheet stock, not tubing. All 6/4 bike frames are made from seamed tubing, that is, flat sheets which have been rolled into a tube and welded (6/4 seamless tubing does exist, but it is EXTREMELY cost prohibitive, and no bicycle companies are currently using it). The problem is that the weld reduces the strength and resilience of the tube. In addition, 6/4 can only take about half the "bending" that 3/2.5 can before it's permanently damaged. In the final analysis, you end up with a bike that's at best just a little stronger, but less able to absorb punishment - plus it'll be a LOT more expensive. Seamless tubing is the preferred type of tubing used for most structural members in the manufacture of high quality bicycle frames.

Titanium is a metallic element whose unique properties including high strength, low density, excellent fatigue and corrosion resistance and low modulus make it the ideal material for bicycle frames. Developed primarily for the aerospace industry, titanium alloys have also found a growing use in Medical, Petrochemical, Pulp and Paper, Architectural, Naval and Sports applications. Titanium itself is not rare but actually very abundant with large deposits occurring in Australian beach sand. However, titanium's extreme reactivity with oxygen makes it difficult to produce in metallic form and it is a long and expensive process to create the seamless tubes used in frame construction.

Airborne utilizes an alloy of titanium with 3% aluminum and 2.5% vanadium, known as Ti-3Al-2.5V or simply Ti-3-2.5 for all of the tubing frame members. This alloy was developed for use in high pressure hydraulic lines and is found on virtually all new commercial and military airplanes being built. Ti-3-2.5 is a balance between the higher strength but less ductile titanium alloys used in aerospace and commercially pure titanium grades which do not offer enough strength to be used in thin-walled tubes.

The high strength and low density of this alloy allow for the building of frames that are not only light weight but also extremely strong and durable. Titanium does not break down, rust or corrode in any type of atmospheric environment and it's high fracture toughness and fatigue resistance result in a frame that can take a pounding and will not fail.

Another unique property of titanium is it's low elastic modulus. The elastic modulus is a measure of how stiff a material is and is directly related to a material's ability to transmit shock waves. Titanium's low modulus translates into a natural dampening effect on vibrations and shocks which allows titanium frames to have a smooth ride even without additional suspension elements. The combination of titanium's high strength and low modulus make the material very "springy" and in fact aircraft springs were one of the first uses for titanium alloys. Because of this spring like effect, the material allows for good energy transfer and does not sap energy from the rider like a suspension system or weaker frame materials will.

Ti vs Other Materials
Lightness, stiffness, and fatigue life are all self-explanatory, while "Ride Quality" is a little different. Basically, a higher number corresponds to how well you might feel after a long 5 hour training ride. The materials that score high "dampen" road vibrations and "soften" an otherwise harsh ride, while those that score lower tend to "beat you up" or transmit all of the road shock and vibrations straight thru the frame and into your body. Yikes! So, basically, Ti is not the lightest or stiffest (aluminum and carbon fiber win these categories), but your body will certainly appreciate the ride quality, and your wallet will appreciate the fact that you may never have to buy another frame again.