Trakhak

I believe it was Gerald O'Donovan, Raleigh's chief frame designer in the 1970s, who was reported in the "Custom Bicycle" book to have said that, based on customers' requests for custom frames, there must be some oddly shaped characters out there. I was reminded of that when I read a bike-sizing post in another thread where someone claimed to be 5' 7" with a 32.25" cycling inseam.

He might have measured accurately, but if so, I'd think that would make him an outlier among adult males.

Do any of the custom framebuilders recollect encountering customers who insisted on your building their custom frame based on their own self-reported measurements, even when you're dubious about those measurements? Or have you all devised fool-proof methods to ensure that the measurements you're given are accurate and reliable?

Doug Fattic 

I never trust someone else's measurements ever. I've found that they can be inconsistent with my own measurements. Even in my frame building classes I'll have students help measure each other and then when I measure, I can sometimes get different results. The problem is that if the customer makes an error (or just does it differently) than the frame I made may not be optimal for them and my reputation takes a hit for their mistake. I should also say that the most important measurements I take are the seat, handlebar, pedal relationship on a fitting bike. Many years ago I realized that 2 people with similar measurements may have a different position. I build a frame off of position and only secondarily off of body measurements (and usually as a double check).

Many of my typical customers can frequently be outside the norm (which is why they want a custom frame) and so a good fitting with a special frame design must reflects their fit and purpose. I am not willing to trust that most important aspect to someone that might not be as particular. Of course this means a on site visit that probably limits your marketing base. I don't have a problem with that.

Btw, your illustration of a 5'7" person with a 32.25" cycling inseam is a perfect illustration of this problem. My measurements are similar but of course I don't know what the definition is of a "cycling inseam " so I don't know if my measurements compare or not.

Trakhak

That's the best short account of the correct way to determine correct frame dimensions I've ever read. Not surprising, given how experienced a frame builder you are. I'm not a frame builder, and it's been years since I worked in a bike store, but I did figure out back then that a good fit on a bike means a good position, where the rider's hands are resting on the bars with only a few pounds of pressure on average.

"Cycling inseam": the person who used the term in the other thread that I mentioned said that it means the distance from the top of a book held firmly in your crotch to the floor. Not clear to me whether "in the crotch" refers to the most prominent bones there or to the soft tissue above and between the bones to the floor.

If I were to attempt to devise a more foolproof method to measure effective leg length, I think I'd (i) mount a bike on a stationary trainer with an appropriate saddle installed, (ii) measure the distance from the saddle contact point to the floor, (iii) have the rider (in bare feet) sit on the saddle and let their leg dangle, and (iv) measure the distance from the ball of the foot to the floor. (I suspect that the degree to which the dangling leg stays slightly bent can be used to determine the correct saddle height.)

Doug Fattic 

A "Fit Kit" (The New England Cycling Academy - NECA for short - kit to determine bike fit) measurement is similar to your book in a crotch. You pull a stick all the way up into your crotch and measure to the floor in stocking feet. That seems simple enough right? But over the years what I found is that some people don't pull the stick up as far into their crotch as they could - maybe fearing it will hurt or they won't be able to father children anymore. That difference in how far one is willing to pull up a stick can be a couple of centimeters. That is a lot. Then someone could be confused about if the should be measured in riding shoes or bare feet and even how far apart to spread your feet. And of course the measurer may be a bit careless about bringing the tape straight down and maybe forgetting to add the diameter of the stick. And if the tape is in inches and they are converting it to millimeters something might have gotten lost in translation. Furthermore if one is using a metal wind up tape it might be a bit challenging to know exactly how to read the bend of the tape where it hits the ground. So now you can understand better why it is I measure a customer myself.

Here is another potential problem with a customer or student self reporting their bicycle position. This knowledge of them knowing their best bicycle position may have been compromised by the design of the bicycle they are riding. In other words they may have found their best position on their bicycle but that doesn't mean it is the very best position possible if they had a custom bicycle. This is where a fitting bicycle becomes important. Their fit problem might become magnified as a rider ages and gets fatter and less flexible. In order to find a comfortable position where their weight is balanced over the pedals so they don't have excess pressure on their hands, they may need to raise their handlebars (and maybe shorten the distance between their seat and bars) and move their saddle back. His/her traditional frame geometry may not have had a shallow enough seat angle or long enough head to place his saddle and stem in its most ideal position. They may not have realized that their position was in fact compromised by the frame they were riding until they have had the chance to compare positions on a fitting bike that has more fitting options.

Andrew R Stewart 

This thread speaks to the challenge builders have for all time. How to measure, who to trust dimensions if the builder doesn't do their own and what to change from the customer's current set up and preconceived notions. Some builders will only work with certain "fitters" they have faith in. Others only build for those they can measure/visit with. Some don't seem to make much distinction. Some are good with letting the customer tell them how to design the bike. This last segment is another topic I think.

When I was a LBS sales guy (when I wasn't turning wrenches) I would make a point of figuring out how the customer was straddling the bike, clearance wise. Phrases like "touching", "Firm pressure", "can't pull the bike up any more", "can you tip toe and pull higher" were all used and helped define the amount of clearance. Long distance this is way more vague. Andy