Originally Posted by
1Lieutenant
I purchased the R300 because of the Ti being 3Al/2.5V alloy. This is certainly not the stiffest, but the tube shaping makes for stiff frame without harshness. So much of the perception of flexibility is due to rider strength, weight versus the frame design. To put this in perspective, I am 67 years old and weigh 145 lb. A 30 year old at 190 lb may have a completely different viewpoint. The Lysnkey R500 with Ti 6/4 is far more rigid for a stronger heavier rider but would totally lose the compliant ride other bicyclists would be looking for.
I completely agree that stiffness is a perception of the rider. One factor you left out is the frame size. Bigger frames have longer tube segments so more leverage to flex. A smaller lighter rider on a smaller frame will have a totally different experience than a tall heavy rider on a large frame.
There's a pernicious myth that 6/4 is significantly stiffer than 3/2.5. You don't need to believe me and can verify by looking up alloy properties from all over the internet. Look up modulus of elasticity.
6/4 is 20% stronger but 0-7% stiffer than 3/2.5. That stiffness difference is small potatoes compared to what is achieved by a small change in tube diameter (remember tube stiffness grows with the 4th power of the diameter, it laughs at a puny 7% change.)
The extra strength of 6/4 means its possible to build a lighter frame from it at same strength but that is only by making the tube walls thinner which will make the frame more fragile than a thicker walled 3/2.5 bike.