Originally Posted by
guadzilla
Also, re your recommendation - wouldnt a beefier downtube make more sense, for power transfer?
Re dents - what kind of risks are we talking about? On crashing or through normal usage with stones hitting the downtube, for example? If it is a greater chance of crash damage, i am not too worried - can always send it back and have the tubing replaced, if it comes to that. If it is damage from just riding around, that's a different story.
If she's less than 110lbs then I doubt she can produce enough watts to require a big down tube. I'm perfectly happy using the same down tube on my bike and I'm 165lbs and ride a much bigger frame than her. Remember, a frame for her will also be small. The smaller front triangle will be stiffer anyway. All you're doing is adding more weight and actually increasing the chances for the tube to dent by going bigger. Larger diameter tubes are more prone to denting than the same thickness tube in a smaller diameter.
IMO, the bigger tubes you see on steel bikes these days are just following the aesthetic trend of beefy tubing found first on aluminum, then ti, and now carbon. Steel doesn't need to be as big to perform the same.
I suggested using a 9/8" .7/.5/.7 downtube. That'll be just fine against road and gravel debris kicking up. I like to add a bit of clear protective tape to the underside of my frames that see off-road use, just to protect the paint.