I’m shopping for a new road bike with endurance geometry (more upright position and shorter top tube), 9mm drop saddle-to-bars. I’ve had a Guru fit done by a professional fitter. The main problem is I’m 5’5” with 29” inseam, and one arm is 2” shorter than the other. So it’s been hard to find a small frame with a short enough reach and tall enough head tube (enough stack) to put the bars close enough without compromising handling.
Most of the 48cm or 49cm frames I’m looking at have a top tube that is too long and/or the head tube is not tall enough. Many 50cm frames don’t have enough standover clearance. The fitter has spec’d a 70mm 6 degree stem as a minimum and doesn’t want to go shorter.
I thought it might work to use a 70mm stem with a 25 or 30 degree rise, to effectively reduce the reach and get the handlebars high enough. It’s sort of like making the head tube taller and the top tube shorter, but with a riser stem. However, my fitter has advised against this, saying that using a riser stem with that much rise may adversely affect handling and weight distribution.
My question is, how is using a stem with 25 degree rise different from having a frame with a taller head tube (more stack) using a 6 degree rise? Is there a handling difference, and why?