EXiT Stack/Reach numbers puzzling

Triathlon Forum
1

First post, looking forward to the expertise here!

I am 45, 5’6", male and completed my first IM 70.3 this past April in Galveston TX (actually turned out to be my first tri ever thanks to hurricane Ike, but that is another story) which I completed on my road bike. The IM was the carrot for a new Tri bike which I am shopping for now. After visiting many LBSs in the Houston area comments were I needed to be on a pretty small bike (duh). Being an engineer I just had to have numbers to look at for comparisons between frames to narrow down the contenders, so I got EXiT fitted yesterday and the results puzzled me:

I was told my stack/reach: 51.5 / 44.3

After the fitting we went to look at s/r numbers here on slowtwitch and the sales guy was talking about pretty large frames for me (examples I was given: Orbea Ora 51: 51.2/39.5 & Quintana Roo Lucero Medium: 51.4/40.7, to meet the stack number). Now, remember I am 5’6" tall with ~29" inseam…the standover height of the QR in medium is an inch taller than my inseam. Does that sound reasonable?

If I go a size smaller like in the examples below, how much can I increase the stem length before adversely affecting the balance of the bike?

Example bikes I was looking at that would allow room to go steeper but would need longer stem:
Cervelo P3C 51 = 48.2/40.5 (has 70mm, needs 38mm more stem)
Kuota Kalibur S = 49.8/39.6 (has 90mm, needs 47mm more stem)
Orbea Ordu 48 = 49.7/37.5 (u/k stem length, needs 68mm more stem)
Argon18 E112 S = 49.5/41.1 (has 65mm, needs 32mm more stem)

Comments are welcome, thank you!

2

First off, I have no idea what an EXiT fit is and I am not a professional fitter.

If an EXiT fit outputs the correct stack/reach of a frame that is ideal for you, then why even worry about the mfgr’s frame size? Just go by S/R.

By doing this, it seems like a 56 Kalibur (51.5 / 43.9) or a 56 P3/P4 (51.6 / 43.3) are better fits.

Now what seems strange to me is a person 5’6 would ride any 56 frame…regardless of mfgr and their varying geometries. Again, maybe the output of the EXiT fit doesn’t tell you frame size. I’d call the fitter and ask if those numbers are frame size or the relative posistion of the arm pads to the BB (or whatever two points).

Something doesn’t appear to add up if its those are frame size numbers IMHO.

Best of luck
-Tim