Yup, multiple factors at stake. Ti weighs about 1/2 of steel, yet is 1/2 as stiff. Alloy is 1/3rd of steel and 1/3rd as stiff. So typically when you end up designing parts from steel, titanium and aluminium to be of similar stiffness, you end up with similar weights. This is a stiffness-to-weight measurement and they're all about the same.

Strength is a completely different matter and you can use stiffness-to-strength as a measurement metric. Depending upon the alloy, ti may or may not be as stiff as steel for the same strength, same with aluminium.

Ken Carpenter, a super-burly track racer from the '80s through '90s was always complaining about whippy wet-noodle bikes. He had a custom titanium track bike built with ti forks. They used thick oversized tubing everywhere and he was finally satisfied and declared, "Now that's stiff!" after a test ride. Of course, the bike was not significantly lighter or heavier than a similary-stiff steel or aluminium bike.

Due to the military usages of titanium, costs tends to be high due to mil-spec testing and manufacturing specifications. It's come down tremendously over teh past decade due to many military-contractors making products for the private-sector. But Ti is still much more costly of a material than either steel or alloy to use. So another measurement we can come up with is perhaps stiffness-to-cost ratio or strength-to-cost.

Only with a material with higher modulus and strength than steel can you make something stiffer, stronger, and lighter. This brings up another measurement of stiffness-to-strength-to-cost ratio (not sure how to plot 4D graph)...

Here's summary of materials properties that I came up for some other discussion:



This hasn't even touched upon the design of the structures. Which has a bigger impact on the strength & stuffness of a shape than the materials used. If you want a light stiff fork, you can make one out of 1" tubing in either steel, titanium or aluminium and it'll be light, strong and stiff. It'll also rattle your teeth loose over bumps as well and give your wrists, elbows and shoulders carpal-tunnel syndrome or RSI...


Well... look at the materials properties. Let's say you make a steel and titanium fork for comparison and you make them of exactly the same shape and design to remove 3D geometry from the comparison. Making it from 6al-4v titanium would result in a fork that is about 1/2 the weight of steel for roughly the same strength. It'll also be 1/2 as stiff as well... hench where the "forgiving" nature of titanium comes from; its higher-strength allows less material to be used for the same strength at the cost of stiffness.