Not really. What most scientists and business people refer to as trial and error is not starting a new experiment from scratch each time. It's learning from the result of a previous attempt, and refining the goal or expectation for the next one. To find a person's preferred position, you'll start at a given point that you think is close to correct, then ask them how they feel and what they would like changed, then make changes based on their input. You tried an input, found an error, adjusted, and tried again. This is both iteration and "trial and error." Same concept, different vernacular.

I've been told I'm a terrible story-teller and poor at explaining things, so I may just be failing at this here. To me, iteration and trial and error are synonymous, as no intelligent person would neglect past experience when coming to an informed decision. Both require continuous experimentation and refinement to come to an optimal result.

No. This not at all what happens.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

If by "fit" we mean getting someone into a comfortable and sustainable position that follows generally accepted aero principles, that's accurate. If by "fit" we mean a position that is highly optimized to maximize aerodynamics based on testing (whether it be field or wind tunnel), most people that have a really low CdA have followed an iterative process rather than a "one and done" fitting.

Please enlighten me to the process then, as my understanding must be off (I'm not being sarcastic here, I'm genuinely interested in being educated). I gleamed from your explanation of trialing changes (e.g. an optometrist) to mean there was a lot of back-and-forth between fitter and client, with a position evolving over the course of a fit session (or multiple sessions).

I have had a professional fit done, but it was an award for winning the overall at a local tri, so 1) I wasn't the typical client and 2) my bike was highly rigid in its positioning (integrated stem bars, slammed and cut fork, nearly maxed out seatpost). We came away with 2 adjustments to perform - raise saddle a bit and increase cockpit length, both of which I already knew should be addressed after a couple hundred hours in the position, but dropping coin on a new frame or post and cockpit was out of the question. Most of the improvements which related to tangible speed gains came from field testing and trialing front-end adjustments in relation to aerodynamics, which is simply not possible in a studio setting.

As Eric pointed out, an iterative process still isn't 'trial and error'. I might see the same rider in the fit stand several times over the years (or maybe even within the same few weeks), and each time the rider was able to bring more data to analyze. The addition of new data helped to us to arrive at a more informed fit, but it didn't change whether something was right or wrong when it came to putting them in an orthodox position.

And while the strategy to improve aerodynamics you mentioned is certainly useful, the vast majority of any aerodynamic gains can be determined by a trained eye - the "eyeball wind tunnel". Field testing, at least for most of my fit clients, told me more about whether they were holding the position on the road that they held in the fit stand and less about whether position X was better than position Y.

In my experience, testing was more useful for assessing equipment, equipment position, and making cost/benefit decisions when it came to equipment choices. Others on this forum are far more informed on aerodynamics testing than me, so maybe my opinion is purely anecdotal.

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Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)

Noone wants to have a stab a this question?

I never looked at the generic sizing chart manufacturers published when doing a fit for a new bike. However, I did see quite a few bikes when the rider didn't get fit first and wanted to get fit after purchase that were problematic. For example:

• Canyon was almost always at least 1 size (and occasionally two sizes) too small. I found this to be the case with both tri and road.
• Nobody that brought in a new Speed Concept ever got the right front-end unless we did a Fit First fit.
• A few Shivs just didn't fit at all - not enough reach.
• Old P3s and P4s were almost always a size too small (and occasionally, too long altogether).
• Had to tell one guy the 15k Pinnarello he ordered not only didn't fit, it couldn't even be MADE to fit. He needed something like 12 cm of armpad pedestals to make their largest TT option even in the ballpark. Pinnarello initially scoffed but when the fit report with fit coordinates was sent, they agreed and refunded the guy his money (to their credit).

Sometimes the problem was the chart. Sometimes it was the shop the bike was purchased from. Sometimes the problem was a buyer mistake.

A lot of these times, we just had to 'make it work'. But you should never have to resort to 'make it work' with a new bike purchase. What's the point of buying a new bike if you aren't going to get one that fits right?

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Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)

I don't disagree. I'm just trying to get a feel for what percentage of cases that happens in. Surely there are many people turning up on the right sized bike?

90-100%

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

Is that specifically tri/TT bikes or including road bikes, etc?

Note first that what you might think I’m doing and what I’m actually doing aren’t necessarily the same thing.

I don’t always eye doctor. Sometimes I do client led. Other times I do “drastic measures” or “instant slam” or sometimes I go “off the charts imaginary bike” to tease things out. My approach depends on the client. It’s sales. Postural coaching and instruction. How will the client best receive the themes and message?

That said, what I’m *actually* doing is going from the current system to the desired system in feasible acceptable manageable chunks or iterations. This is a process, part of a larger system designed to fix a certain problem, informed and guided by a well developed philosophy.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

So are you saying the size charts are wrong (presumably recommends a bike too small) or that a size chart isn’t feasible? I would have thought orthodoxy would put many people on a reasonably linear band on the XY chart, not a wide scatter plot?

Mostly tri. But then again I’m taking advantage of what’s made possible by bike companies, and not making And marketing a bike. Very different things.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

I remember when I lived in SoCal and how premium denim brands wouldn’t make certain sizes. Now they do.

Alternately, the worst running shoe on the NYT Alphafly research chart had marketing copy saying it was the best and people ate that up.

Some notes:

You’re assuming the charts’ purpose is to put you on the right sized bike.

You’re also assuming the charts correlate to lagging indicator orthodox bike positions.

You’re also assuming orthodox bike positions have something to do with bike sizes.

Go look at and understand the Canyon fit thread and report back.

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

I just bought a bike and my fitter ordered my size based on my professional fit. I was riding a small Argon 18, which I already knew was too small. I thought I was a medium and Argon told me I was a medium. I ended up in a large and was floored. The bike and fit feel great though. This leads me to believe size charts are not fit charts and that your comment referring to 90-100% is totally correct. Fit is very individual and varies based on the individual, make and model. This is why you get a fit before buying.

Congrats! This makes me soooo happy!

E

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

So then the follow up question is what proportion then fits a smaller and which a larger size frame?

Instead of smaller or larger I prefer to think of it as optimized

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”