Articles - Fit Kit Systems

Sizing. What a Frame Builder Wants to Know.

If you are bike fitter, or dealer for one of the larger custom brands like Waterford, Seven or Moots, and have a client who wants to get sized up to order a handmade bicycle, you need to find out what information the frame builder wants. Many will have a client order form which details this, but others don’t. Ask your client to ask the builder, or contact the builder directly.

I took the opportunity to attend the North American Handmade Bicycle Show held in Salt Lake City in March 2017 to meet up with frame builders and ask them what information they wanted from clients to ensure the bike was built to ensure a good fit between human and machine.

As expected, answers varied but there were some consistent and recurring themes. Frame builders want to know where the cyclist’s bike-body contact points are in relation to each other when in a riding position that feels great. Ideally this comes from a “reference bike” on which the cyclist already enjoys a good riding experience. The 4 key measurements from a reference bike are:

Saddle height (from bottom bracket)
Saddle set back (tip of saddle nose behind bottom bracket)
Saddle nose to center of handlebar at the stem clamp
Saddle to bar drop (height of the top of the bars relative to top of saddle)

If the customer does not have a reference bike, or does not feel good on their existing bike, then the same measurements can be obtained using a size cycle / fit bike. You may also end up with measurements like Handlebar X and Y and Saddle X and Y if you are using a Fit Bike to find a good riding position for a customer.

Some builders will ask for a lot more measurements and rider information. An experienced frame builder will be asking about the customer’s current bike, what their current fit position is (same measurements from above) and how they feel on their current bike. They may also ask for body measurements of height, foot, inseam, torso, and arm length. This is where the Fit Kit comes in handy. From all this information they will determine how to position the cyclist for a better riding experience, and design a frame to achieve that fit position, considering weight distribution, bike handling and responsiveness.

Although handmade is often synonymous with “custom”, this needs to be defined. Not all handmade frame builders offer the same level of customization. Custom can refer to:

Frame material selection (steel, titanium, carbon) and tube joining (e.g. lug or fillet)
Geometry and sizing, specifically for your measurements
Paint job / graphics
Components (drivetrain, wheels, etc)

Most builders specialize in using a single frame material, and in choosing the frame builder, a cyclist is choosing the frame material. Typically there is a choice of component packages or build kits, or a menu of component choices for the cyclist to choose from, as well as the color of the bike. However not all handmade builders offer custom geometry. That is not an issue for people who lie in the middle of the bell curve for height, weight, proportions, health and riding style. But if the rider is an outlier who has trouble getting well fitted on a stock production bicycle, they are a potential candidate for custom geometry.

Frame builders with a long established reputation like Richard Sachs and Roland Della Santa make a signature frame, and their customer is buying that frame geometry and their craftsmanship in making it. Customization is limited. Other frame builders like Carl Strong go to great lengths to understand their clients riding experience and future intentions, and design a bike that is exquisitely built for them.

Most bike fitters are not frame builders, and most frame builders are not fitters, but they offer complementary services and can help each other out for the benefit of the rider. The best fitters understand bike geometry and handling very well, and the best frame builders have a good understanding of fit. When a cyclist is corresponding remotely or indirectly with a builder, a fitter can serve a useful role in the pre-order and post-delivery phases of a custom purchase.

When a cyclist takes delivery of a handmade bicycle (or any bicycle for that matter), the fit still needs to be dialed in, but this can be achieved without gross distortions of the stem or seat post as the bike is designed to be a close fit, and it will look great and ride better, like a mechanical bespoke suit.

It’s Not About the Numbers

It’s not uncommon for the Fit Kit System to be dismissed as a “formula fit” by people who themselves are advocates and users of bike fitting data, measurements, calculations, numbers, and yes, formulas. Mathematics has been a tool for solving many mysteries of the planet and universe and in engineering remarkable accomplishments for centuries.

Numbers, formulas, averages and equations have a role to play in predicting a bike purchase or fit position and they may be applied to frame geometry e.g. stack and reach; bike set up, e.g. saddle and handlebar X/Y; or body position, e.g. leg angles. Bike fitting has become very mathematical, aided by video and motion capture analysis, and Excel spreadsheets of trigonometric relationships.

The math serves a role to inform, educate, estimate, advise and communicate. But here’s the thing. A bike sizing or fitting is not about the numbers, it’s about the rider’s experience. It’s about the human experience – with each other, with a bike, with the sensation of riding on a road or trail, in congested traffic or in serene surrounds.

The science of fitting involves numbers, because numbers are a language of science. But the art of fitting involves connecting with our customers as fellow cyclists, understanding their pleasure and pain, and guiding them to favorable experiences on their bike.

If you are using the Fit Kit System to help sell a bike, you are using it to do more than create a sales transaction. You are using it to create a dialogue, a conversation, a relationship. The measurements and projections are a vehicle for this. It’s a lot more than a formula.

If you are using the Fit Kit System in a bike fitting situation, it should be just one of many tools, because the Fit Kit System itself provides just a slice of data, not the full equation. You also need to understand and connect with your customer, observe, ask questions, engage in dialogue. And you will probably be taking other measurements as well.

Bike sizing and fitting is a process, that follows a method. It’s not a formula, even though a formula may be a part of the process. Bike sizing and fitting is a personal service that requires skills. Those skills include using information and technology. The technology can be low tech and analog like the Fit Kit System, or hi-tech and digital like the Retul or Guru systems. But many other skills are also needed. A bike fitting system is a useful resource, but systems and formulas don’t do the fitting. Skilled people do. The great pyramids weren’t built by mathematicians, but they couldn’t have been built without them either.

Reliable, Repeatable Measurements

Being able to measure people and bikes is a core skill for those of us involved in bike sizing and fitting.

Why are we measuring? To record and document “before” and “after” changes; to project recommended bike sizes and models; to advise on fit components.

A bike can be described by its measurements, and the changes are relatively small from one size to another, and from one shape or model to another.

A person and their fit position on a bike can be described by measurements as well. Again, small changes can make for a big difference, which is why it is important to be able to measure consistently, accurately and reliably.

Much of the responsibility for accurate measuring has been passed onto technology. i.e., we believe what we see on a screen with data flow from video analysis and motion capture. However these systems are not infallible, and it helps to be practiced with hands on measurements, which are required if you are using an analog tool like the Fit Kit. A practiced human is more accurate than a poorly calibrated machine, and has the ability to interpret the numbers and have a good idea if a measurement is “off”.

As cycling season starts to get underway in much of the northern hemisphere, you may be dusting off your Fit Kit tools and getting ready to use them. Now is a great time to practice locating the key body measurement points, and getting a refresher in using the tools. Practice on different body types. Practice on other staff. Repeat the measurements on the same person 3 or 4 times over a few days, recording the information separately each time, and then comparing the variation at the end. You should be within a few mm each time.

If there is wider variation, explore why there are inconsistencies. The subjects clothing and posture, and your instructions and technique can all contribute to variation. Reduce the variations and improve the reliability of obtaining repeatable results. Measure twice, cut once is a good motto to keep in mind.

Assessing the Body: 4 perspectives to help with bike fitting.

Improving a bike – body relationship involves developing a deep understanding of all three aspects: the bike, the body, and how they interact and relate.

Let’s focus on the body. Whether it is a pre-purchase sizing or an in-depth bike fit, having a structured approach to assessing the rider’s body can save you time and help marshal your thoughts to guide you to effective recommendations.

The 4 perspectives of body assessment are:
1. Skeletal
2. Muscular
3. Adaptation
4. Pre Existing Conditions

Each cyclist is different in many ways, and without a structured approach to assessment, it is easy to overlook a significant contributor to an appropriate bike fit. To build up a holistic understanding of our bike fitting client, it helps to consider the parts that make up the whole from a number of different perspectives:

1/ SKELETAL
The skeletal layer is the framework on which all other layers are added and function. It provides a baseline of information as to what is possible and viable, or not. It’s more than inseam or height, it is about both absolute and relative proportions. Long legs, short legs? Long arms? Short arms? Sit bone width? Shoulder width? Skeletal measurement information provides valuable data to help with recommending a bike size and to solve fit problems.

How to assess skeletal measurements?
The Fit Kit System measuring devices provide reliable data quickly and simply. Some other companies also supply manual measurement tools, as well as digital tools based on body scanning or 3D cameras, such as that in the Guru system. The advantage of a physical, manual method is that you (or the rider) are physically locating the measurement points, the rider is actively engaged in the process, and it can lead to additional information and insights.

Interpretation
Skeletal, anatomical measurement information defines what relationship between the bike contact points is biomechanically viable based on that person’s structure. Frame size and geometry, seat height, reach and drop are all going to be defined in the first instance by what is skeletally achievable.
What’s achievable may not be desirable or optimal, so let’s add another perspective:

2/ MUSCULAR
The muscles (and associated connective tissue) move the bones of the skeleton. A rider with well conditioned muscles, a good range of motion and highly functional movement patterns can move the skeleton into sustainable riding positions that are not an option for a rider with weaker muscles, tightness or imbalance.

How to assess muscles?
There are a number of approaches to gaining information about the person’s muscles as relevant to riding. From quick and simple to longer and involved assessments, the method you use will depend on the depth of information you need and your training and experience in applying these:
• Basic flexibility assessment
• Posture and gait assessment
• Passive range of motion tests
• Active mobility and stability tests
• Functional Movement Screen
• On bike observation, including posture, muscle engagement, joint angles
• Asking questions about soft tissue aches and pains

Interpretation
The strength and flexibility of the muscles and associated connective tissue (tendons and ligaments) are going to determine the effective movement of the skeleton.
Take the same skeleton. Apply a different muscle assessment, for example, tighter hamstrings. This may result in a lower saddle height, and shorter reach and drop.
The role of the muscles is also going to change by how adapted the person is to cycling.

3/ ADAPTATION
Adaptation modifies the muscle functioning and fatigue resistance.
As bike fitters we generally want to adjust the bike rather than force the body to adapt. However putting a body on a bike requires the body to make some adaptations. Adaptation is going to be influenced by:
• Time on the bike (cycling history and experience)
• Training, exertion
• Bike type and riding style
• Participation level / Event type

How to assess adaptation?
Ask questions to gain information. Questions like:
• How long have you been riding, how often, how far, how hard?
• What type of bike do you ride or will be riding?
• Have you changed out any equipment (shoes, stem, saddle, bike)
• Have you made any adjustments to your bike set up recently?

Implications?
Someone who is new to cycling, or returning after a long period off the bike, or changing from say a mountain bike to a road bike, is going to be less adapted than someone with a long history on the same style of bike.
A novice is likely to be happier with a more relaxed riding position than an experienced rider, as their body has not adapted to the position and muscular requirements of cycling. A more experienced rider will probably prefer a higher seat height and a longer and lower reach.
A highly adapted rider may be resistant, both psychologically and neurologically, to changes in their fit position, requiring graduated change over time.

4/ PRE-EXISTING CONDITIONS
Take all of the above and add a final layer. Body issues and history that are very specific to the individual will often require consideration and accommodation. These are most commonly from injuries or surgery. The event may have been recent, but sometimes so long ago they have forgotten about it. Examples include broken bones, sprained ankles, fractured vertebrae, whiplash, leg length differences, disc degeneration, hip replacement.

How to assess pre-existing conditions?
Ask questions in a pre purchase or pre-fit interview, like:
• Have you had any accidents, injuries or surgeries that would affect your position and comfort on a bike?
• Do you have any spinal problems? Repetitive stress injuries?
• Are you seeing a medical professional or therapist for any sports related issues?
It’s not uncommon for a rider to not volunteer or forget to mention something of relevance. If you observe an odd movement pattern or asymmetry when they are on a bike, ask again. Are you sure you have never broken a bone? Suddenly the person might remember they broke an arm as a 12 year old, or tore an ACL skiing.

Implications
Is a condition going to affect their position, and if so how? What has to be done to accommodate that?
This is going to depend on the situation, but may have implications for cleat shimming or wedging, seat height, reach and drop, the placement of the controls.

Summary
The body is an incredibly complex unit, and riding a bike adds complexity. Having a simple structured approach to building up information about a rider’s body is a useful tool to navigate through the complexity. It helps in creating a strong and respectful relationship with the cyclist, and to offer fact based observations and recommendations that will benefit their bike choice, fit position and riding experience. It’s an intrinsic part of the Fit Kit System and can be a 5 – 10 minute process for a pre purchase sizing or a 45 minute process in a detailed bike fit session.

Back Issues – pre-existing

Back pain is a common complaint from cyclists, and more common than knee problems according to some studies. It is important to distinguish between pre-existing back issues that are brought to the bike, and discomfort or pain issues that occur as a result of cycling.
Let’s just focus on pre-existing conditions for the moment.

Pre-existing conditions are surprisingly common among the cycling population, as the low impact nature of the exercise attracts people with a history of serious back injury. Typical issues relate to either the cervical or lumbar areas. People with broken backs, fused vertebrae and herniated discs are out riding bikes. When sizing or fitting a bike it is important to inquire about any existing back conditions, as this will influence bike choice and set up.

Cervical conditions usually mean the rider has less ability to tolerate neck flexion, meaning they can’t look forward while bent forward. The fit protocol is to have rider in a more upright position. That means a shorter reach, and higher bars. How upright depends on their personal situation and neck stability and mobility.

One cyclist I worked with had broken her neck in two place in a horse riding accident, and could not ride 5 miles without unreasonable discomfort. The only position she could tolerate was bolt upright. I fitted her mountain bike (used only on paved and gravel roads) with a stem extender and short, steep stem. It looked like a frankenbike, but she was delighted to then be able to ride 20+ miles without any pain.

Lumbar conditions vary more widely. Soft tissue only, or not? Fused or not fused? Off bike strength and flexibility vs on bike experience? A suitable bike position is likely going to require some experimentation. A more upright position with less shear stress along the spine will work for some people. However for others this will increase the loading, bump impact and back stress. They may be better with more weight supported through the handlebars. Rider feedback is important, and input and consultation with specialty health providers may be advised. Proceed carefully and with consideration.

I’ve had bike fit customers with fused lumbar vertebrae who didn’t seem to have any additional limitations regarding their fit position, and others who were much happier when their reach and drop were reduced.

Share your own experiences and recommendations by leaving a comment.