My take might be a bit different than that of other fitters, but there are a lot of pieces to the puzzle that is bike fitting. A professional bike fit is a combination of your bike, your body, your racing style, your capabilities, your psychology, and your expectations. Aerodynamics are part of it, but there's also limitations as far as how well your bike fits your body, and how fit your body is to support an aerodynamic position.

A good bike fit is very individual - none of us are symmetrical, and we all have different levels of fitness, things that hurt more than others, etc. Any bike fitter could take a look at you from a side picture and jack your seat up and slam your cockpit to make you pass the eyeball aero wind tunnel test. That doesn't mean you're comfortable enough to ride that for more than about 15 seconds.

Look up some of the fairly recent ST front page articles with Mat Steinmetz and how he has fit Mirinda Carfrae - she's a world-class athlete and he's taken an iterative, somewhat gradual approach to her fit to get her more aero and comfortable within her physical and even psychological limits. But, Rinny is not you or me. 100% of my customers have not been Mirinda Carfrae. Every one of them has been a unique experience (and that's what I love about it). A good fitter like Mat will use the right tools (Retul, BikeFit, FitKit, GURU, motion capture, trial-and-error, experience, a keen eye for detail, etc.) to find the best position for you. For Mat, Retul is a tool, but that is only a part of the experience.

A good fit is one of the most beneficial performance gains you can make on your bike, but be careful not to confuse "optimized position" with "aerodynamic." Your optimized position could very well be aerodynamic, but it also has to be sustainable.

I don't know if that really answered your question, but I hope it helps!

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Travis Rassat
Vector Cycle Works
Noblesville, IN
BikeFit Instructor | FMS | F.I.S.T. | IBFI
Toughman Triathlon Series Ambassador

Well, it depends. For me, "optimizing fit" for aero means finding the most aerodynamic position I can hold for an hour and produce maximum speed. But that's me and I don't do Tri; I do TTs.

As a fitter, I think you have to take into account the distance the racer plans on doing. A less aerodyminc position, but one that can be held for the duration without negatively impacting the run is key. I've found that adding 3-5mm of spacers for a half works for many. 5-10mm for a full has similar results. Both compared to a more Sprint or Olympic oriented fit.

I have a friend who's not very flexible. He's running almost no drop, but is still over 24 mph for a half in a relay, at 55. I had originally fit hit with 6cm of drop and he performed poorly and was not comfortable. So, he's not optimized for aero, but he is optimized for speed.

I'm not sure I've answered your question, but I hope I've provided something useful.

One of the better responses to a bike fit question ever on ST.com

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