Originally Posted by Rudebob

This article is so poorly researched and written, it has no credibility. Furthermore, it wreaks as a marketing tool which would infer input from the two manufacturing sources cited. If that is in fact the case, it shows that the companies manufacturing these frames also know very little about titanium alloys as well.

First of all, the author indicates the primary benefit of titanium is fatigue resistance with a direct inference that titanium alloys cannot fail by this mechanism. This is a completely false notion. Titanium alloys fail by fatigue mechanisms all the time. Don’t take my work for it-Google it. Obviously the author did not. The main benefit of Ti alloys is strength to weight ratio, moderate corrosion resistance and elevated service properties along with lesser tangible benefits such as ride "feel", “coolness” factor of a “magic alloy” that marketers have done so well in convincing consumers to embrace, and echelon status based on cost, to name a few.

The author then tries to impress with his knowledge of alloys asserting 3 specific categories of material, when actually only referencing specific alloys-when in reality there are dozens (actually, CP Ti is technically considered unalloyed). While right in one respect, titanium alloys are often classified as three distinct alloy groups: alpha, alpha-beta, or beta class alloys, the three alloys he lists are the most commonly used: CP (Grades 1 - 4), 3Al-2.5V (Grade 9) and 6Al-4V (Grade 5), not categories.

He then suggests that 3Al-2.5V (Grade 9) is best for cycling applications citing a number of valid reasons but ignoring the most obvious-cost. This alloy is used because it is commonly produced for sporting good applications and is therefore, produced within cost parameters to make it feasible for these applications, albeit still expensive. However, if I was to go to the trouble and cost of building a titanium bicycle frame I would use 6Al-4V for the added benefit of better strength to weight. Titanium frame manufactures typically don’t use this alloy as a cost savings because it is produced primarily in aerospace applications-not because 3Al-2.5V is better.

Where the author really screws up is to suggest that not all 3Al-2.5V alloys are the same citing three variations and referencing aerospace specification “AMS 105". This is flat out wrong. There is no AMS 105 pertaining to titanium or any alloys for the matter. The AMS system of alloys uses a 4 digit numerical postfix. The three AMS specifications for this alloy are AMS4943, AMS4944, & AMS4945. The author is right in that there are 3 grades of 3Al-4V, Grades 9, 18, 28. The only difference is that the latter 2 grades contain Palladium and Ruthenium, respectfully, that further aid in corrosion resistance. However, these alloys are all perfectly suited for the frame building, and I would doubt the latter have even been used in bicycle applications.

Yes, titanium is more difficult to produce and process than most other alloys. Yes, there can be impurities, including interstitial gasses such as oxygen, nitrogen and hydrogen that can make these materials problematic. However, in the simplest terms if these limits are exceed, they are non-conforming and technically not 3Al-2.5V or 6Al-4V.

IMO, the most common problems in processing titanium is oxygen contamination (alpha-case) when welding and/or heat treating. Yes this is a very real problem that should be addressed-maybe in another thread. This is why I would never own a titanium frame without knowing how the material was processed, specifically welded. However, this has no bearing on the quality of the material. One of the other more real common problems is not inferior materials but the wrong materials. Raw material stock gets logistically moved from the mill, multiple shipping sources, material brokers (maybe more than one), and then on to the end user where it gets transferred back in forth between shifts, etc. With all this material in transition it is not uncommon for a wrong tube, bar, rod alloy to get stacked, racked or binned for a different material. Just saying.

'bob