Fitting question

Good afternoon,

Taking a persons measurements and then designing a frame from these has got me quite confused. I've done a lot of online research, read through Paterek's info and have played with the fit advisor in bikecad pro.

There seem to be a variety of different approaches to how to properly design a frame based on an individuals body type, flexibility, riding style, etc...

Perhaps I am overly complicating this, and need to just stick to taking measurements that translate to stack and reach and then tweak based on other variables such as flexibility, riding style, etc?

I'd greatly appreciate it if someone could shed some light on which body measurements I should be taking, and how I can then calculate and apply these to frame dimensions. If there is an online or print resource you would recommend to save time in replying, or if I missed a helpful thread here on velocipede that would help, I would appreciate that as well!

Thanks so much!
JD

This a great topic for discussion. As far as I'm concerned, there is no substitute for experience. What is your background in riding/racing or whatever if I may inquire?

A gent in PA taught me the game. He insisted that I toss out ever guide or "system" and trust my eyes and ears.

Frame design is out of my pay grade. I can fake it but mot make it.

I'll beg the jaded brethren here to hold your water if you have nothing to add. This question is essentially important for what we represent.

Thanks for the reply Josh

I have been riding most of my life, however much more seriously in terms of miles put on the road over the last 5 years. I started racing a few years ago, and mainly race crits....In comparison to many of you, I would say that I am not an experienced rider or racer by any stretch both in terms of ability and duration.

I hope this gets to what you were asking?

I am hoping to get some information so that I can find a starting point in designing a frame...for example, if a persons torso is "x" long, arms from shoulder to hands is "y", how can I translate these into a general frame dimension which then could be tweaked based on experience or feel as you mentioned.

Here are two bikes I built and painted for myself, utilize the bikecad pro fit advisor as a starting point and then tweaking based on my flexibility and what I am using them for...I would really like to design them more traditionally without using the fit advisor

Attachment 119753

Attachment 119755

The reason you are not getting many replies is that this topic can be radioactive.

I'll broach the topic with I begin every fitting with a long talk about history and expectations than move on to saddle height.

Next.....

They have different length stems, seatpost offsets etc for adjusting fit. There are tried and trued ballpark measurements, the rest is just background noise.

I appreciate that Josh...yes, in hindsight I can see how this could be such a topic. I certainly didn't intend my question to lead to radioactivity, so to speak, but the best laid intentions.....

When I used to build old triumph motorcycles and old choppers, perhaps this is similar to what type of oil is best.

Thanks as well Bill...I'm trying to develop the proper set of measurements to get to some of those ballparks.....I'd like to try my best to avoid "fixing" an incorrect reach, for example, by compensating with a stem that may end up making steering more sluggish or quick.

Thanks again for taking the time to respond; I appreciate it
JD

I don't use body measurements much in designing my frames. And while I think BikeCad is an excellent product, I don't use it much either. I base my designs off of a fitting that establishes the seat, handlebar, pedal relationship. What I discovered early in my career is that 2 bodies with similar measurements can sit quite differently on a bicycle. My fixture (that resembles a mechanical drawing) can then hold the chosen saddle/seatpost and stem in that same position and I can slide around the pieces that represent the frame tubes to match up with those components.

There are 3 factors in establishing a fit. Biomechanical efficiency, aerodynamics and comfort. These factors can be in tension with each other and choices have to be made which ones are most important. Now days I make (or much more likely my students make) steel frames that prioritize comfort. If one wants to go as fast as possible then are more likely to buy a carbon frame. I can still ride the Masi bike Faliero had made for me in 1972 but I wouldn't want to. I prefer sitting more upright now and my design decisions reflects that choice.

There are 2 basic approaches to frame design. Most studies in positioning and design involve improving performance in competitive conditions. Just for convenience I'll call it the Italian method. The other is a more utilitarian approach and for our purposes I'll call it the French method. Whether it is for recreation or function, this approach emphasizes comfort over speed. This method can be preferred by recreational, urban and older riders. This probably results in a lower BB height, a bigger frame and shallower angles.

If you are in Iowa, your framebuilding journey probably involved learning some things from my buddy Jeff Bock. I meet him on Ragbrai in 1978. Over the years we would often ride a day chatting about building and painting and life.

Here is a picture of my SS laser cut and etched fixture that helps me convert a rider's bicycle position into a frame design. Its accessories and markings aid in creating the design. I've had it refined over many years.

Good share Doug.
You could benefit use of a size cycle. They are certainly "out there" for sale used. That could give you a basis for fiddling with setup(s). I sold mine a few years ago, it was a terrific help in situations where clients did not own a bicycle that we could use as a basis for the fitting.

Talking road bikes here, grab a Derosa or Colnago geometry chart and use that as a starting point.

Quote:

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Originally Posted by Too Tall

Good share Doug.
You could benefit from the use of a size cycle. They are certainly "out there" for sale used. That could give you a basis for fiddling with setup(s). I sold mine a few years ago, it was a terrific help in situations where clients did not own a bicycle that we could use as a basis for the fitting.

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I have several commercially made stationary fitting bicycles. However Herbie Helm (my sometimes teaching assistant) came up with this home made version for those that want to make something themselves. I've posted its dimensions on Bike Forums for those interested. This is a particularly useful tool for those that prefer a comfortable position where the handlebars are near the height of the saddle. This group would include urban (looking down the street instead of at a back wheel) and women riders (needing to take pressure off of the sensitive areas of their crotch) and those old enough that realize they will never win the Tour and just want to ride comfortably. In other words recreational cyclists not on group training rides.

One of the keys for this kind of rider (that is in a common demographic for a custom steel frame) is finding the balance point of their body over the pedals that takes the weight off of their hands on the bars. They are probably going to have a greater amount of saddle setback then their go-fast cousins riding a wonderful handling Italian frame with a seat angle that is at least 73º or more. With handlebars around the height of the saddle, it isn't unusual to have a 72º or less seat angle. That means using a commercially made bicycle for fitting won't allow enough saddle setback to find their balance point.

Of course once the saddle has more setback, there are real challenges to creating a design. Some compromises to a perfectly handling bicycle probably have to be made somewhere. I should mention that some builders believe that an Italian fit is still the best all around option. This difference of philosophies is why a discussion of best bike fit and frame design can be challenging on a public forum. We like to get along.

These are my tools for creating a frame design. The fitting bike establishes the seat/stem relationship and my fixture can help me orient the tubes to match up with those components. This often results in needing to swap out the stem or seatpost. Because my fixture is laying on an alignment table, I can also use it to spot braze the tubes together after I get them aligned on the table.

Doug, thank you so much for taking the time to share your thoughts and experience. This is quite valuable to someone new like me. Breaking down the three factors of fit and two factors of design is really helpful in giving me an idea of how I may want to consider thinking about frame design and proper fit before I put pencil to paper.

Surprisingly, living in the same town, I haven't yet met Jeff. I did call and speak to him a few years ago to pick his brain and he was a wealth of knowledge, and kind to boot.

Quote:

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Originally Posted by Doug Fattic

I don't use body measurements much in designing my frames. And while I think BikeCad is an excellent product, I don't use it much either. I base my designs off of a fitting that establishes the seat, handlebar, pedal relationship. What I discovered early in my career is that 2 bodies with similar measurements can sit quite differently on a bicycle. My fixture (that resembles a mechanical drawing) can then hold the chosen saddle/seatpost and stem in that same position and I can slide around the pieces that represent the frame tubes to match up with those components.

There are 3 factors in establishing a fit. Biomechanical efficiency, aerodynamics and comfort. These factors can be in tension with each other and choices have to be made which ones are most important. Now days I make (or much more likely my students make) steel frames that prioritize comfort. If one wants to go as fast as possible then are more likely to buy a carbon frame. I can still ride the Masi bike Faliero had made for me in 1972 but I wouldn't want to. I prefer sitting more upright now and my design decisions reflects that choice.

There are 2 basic approaches to frame design. Most studies in positioning and design involve improving performance in competitive conditions. Just for convenience I'll call it the Italian method. The other is a more utilitarian approach and for our purposes I'll call it the French method. Whether it is for recreation or function, this approach emphasizes comfort over speed. This method can be preferred by recreational, urban and older riders. This probably results in a lower BB height, a bigger frame and shallower angles.

If you are in Iowa, your framebuilding journey probably involved learning some things from my buddy Jeff Bock. I meet him on Ragbrai in 1978. Over the years we would often ride a day chatting about building and painting and life.

Here is a picture of my SS laser cut and etched fixture that helps me convert a rider's bicycle position into a frame design. Its accessories and markings aid in creating the design. I've had it refined over many years.

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