Originally Posted by
Mark Kelly
Dave,
your argument makes sense, but is it not the case that when presented with a rider profile for which you would choose a heavier guage chainstay in steel (say 1.0 mm instead of 0.7 mm) you could use a heavier guage Ti tube (say 1.6mm wall rather than 0.9). The Ti tube will still be something like 20% less stiff than the steel one but when combined with the higher stiffness of the other Ti main frame tubes (due to their larger diameters) the overall stiffness would be OK.
I see your point and it comes down to degrees I think. Will the bike work even with stays that are 20% less stiff? Of course it will and the rider would probably love it. I look at it a slightly different way and when I design a bike never rely on the main tubes to contribute the the drivetrain stiffness. The main tubes are very ineffective in stiffening up the drivetrain. It's so often overlooked but the chainstays are the only tubes that can transfer the power from the BB to the rear wheel. If the stays are flexi then drivetrain will be flexi and the size of the down tube will make no difference.
Again - going back toe OP's question. He's a big guy and wonders what material would be best for him. I contend he could be happy with most any material while at the same time think that he could be better served by a bike with a stiffer drivetrain......... and making the drivetrain stiffer with Ti is more difficult and less effective.
I make steel bikes but I love all bikes regardless of material. I have an engineering friend who once told me "there is no such thing as a bad material, just a bad application" and to me this makes sense. Riders of different weights and sizes can benefit from different materials and designs. I just like seeing people get bikes that are best for them based on the mechanics and properties of the bike and to not get hung up on a specific material or fad. And of course 'best' or 'better' is a matter of degrees and two things can be great while one of them is a bit better. For a big guy I think steel is better. On the other hand if you are 4'11" and weigh 95# then I think you might be better served with Ti.
Time for leftover pie!
Thanks again for reading.
Dave