Hello to all,

I am looking to build a tri bike for a woman friend. I know it should be smaller than her road bike size, however, she is rather petite and rides a 48cm Specialized Ruby as her road bike with 506mm top tube length. If I look at the Specialized bikes, small size Transition with zero layback post has 452mm top tube length. Is this about the size I should be looking at or should I go for an even smaller size?

I'd appreciate your thoughts on this.