Bike Fit and Optimization
Professional RETÜL Body Geometry Bike Fitting
With more than 20 years of competitive cycling, bicycle mechanics, and retail industry experience, Karel has helped countless athletes improve their comfort, efficiency, and performance through professional RETÜL bike fitting.
Whether you ride a road bike, triathlon bike, gravel bike, mountain bike, or time trial bike, Karel’s deep understanding of all types of bicycle parts and brands will help you achieve the optimal position for your body, goals, and riding style.
A proper bike fit is about more than comfort. It is a critical investment in performance, aerodynamics, pedaling efficiency, and injury prevention. Karel's comprehensive fitting process combines technical expertise with a personalized approach to ensure that every adjustment is purposeful and effective.
Throughout the fitting session, Karel will explain each change and educate you on how your position impacts comfort, power output, efficiency, and long-term durability. His goal is to help you find the most efficient and aerodynamic position possible—without sacrificing comfort or sustainability.
To learn more about Karel's bike fitting process, please scroll down.
Pre-Race Bike Tune-Up & Performance Optimization
Preparing for an upcoming race? Looking to maximize the performance and reliability of your bike?
For more than 15 years, cyclists and triathletes have trusted Karel for meticulous and detailed pre-race tune-ups and performance optimization services. His attention to detail helps ensure your bike is operating at its highest level—smooth, efficient, reliable, and race-ready.
Services may include drivetrain optimization, mechanical inspections, component adjustments, and recommendations for performance-enhancing products and upgrades. Karel offers a variety of trusted products that can be purchased before or during your service to improve safety, reliability, comfort, and performance.
Pricing is available upon request. Discounts are offered for Trimarni team members and returning clients.
Learn More
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Purchasing a new bike—or upgrading your current one—is exciting, but with so many opinions about bike fitting, it can be difficult to know what advice to trust.
You may have heard that a professional fit is essential before purchasing a bike. Others may tell you that a quick saddle adjustment at a local bike shop is all you need. And if you've been fit in the past, you may thinking that a second fit isn’t necessary.
The reality is that a professional bike fit is one of the most valuable investments you can make as a cyclist or triathlete. A proper fit involves optimizing key contact points and components—including saddle height and selection, handlebar position, stem length, cleat placement, and foot alignment—to improve comfort, efficiency, power output, and overall performance.
A bike fit isn't just for competitive athletes—it's for anyone who rides a bike. When paired with the correct bike size, a professional fit can enhance comfort, reduce the risk of injury, and make every ride more enjoyable.
That's why choosing an experienced and reputable bike fitter matters. A quality bike fit is not simply about adjusting a bike—it's about creating a position that allows you to ride stronger, longer, and more comfortably and then dialing in the fit overtime, as you gain strength and skills.
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A pre-race bike tune-up is a comprehensive inspection and optimization service designed to ensure your bike is performing at its best before race day. Key components—including brakes, shifting, drivetrain, wheels, tires, sealant, bearings, bolts, and chain—are inspected, adjusted, and serviced to maximize performance, reliability, and safety. Race day is not the time to discover a mechanical issue. A professional tune-up helps reduce the risk of equipment-related problems, improves efficiency, and gives you confidence that your bike is ready to ride when it matters most. Whether you're racing a sprint triathlon, gravel event, or Ironman, a properly maintained bike can help you ride more efficiently, faster, and with greater peace of mind.
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Performance optimization is the next step after a professional bike fit for athletes looking to maximize speed, power, efficiency, and aerodynamics. This service focuses on fine-tuning your bike and equipment setup to reduce aerodynamic drag, improve power transfer, and enhance overall riding performance.
Areas of focus may include aerodynamic positioning, equipment selection, tire and wheel setup, drivetrain efficiency, and race-specific recommendations like aerobar cups and bottle cages.
For athletes seeking every possible advantage on race day, performance optimization can unlock meaningful gains and help take your cycling performance to the next level.
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Improving bike handling skills is one of the most effective ways to increase safety, speed, and confidence on the bike. Through personailzed instruction, you can learn how to better handle your bike in a variety of conditions, including climbing, descending, cornering, group riding, wind, rain and technical terrain. Effective bike handling skills will not only make you a more efficient and confident rider, but also reduce the risk of an accident and allow you to ride faster with greater control and comfort in real-world conditions.
We partner with brands that align with our commitment to performance, quality, and athlete success.
Through years of coaching, racing, and working with athletes, we've carefully selected products and brands that consistently deliver quality, reliability, and performance. We are proud to be authorized dealers of the following brands:
Ventum
Boyd
Silca
51-Speedshop
Knog
Crank Brothers
Selle Royal
Cobb
Bont
Fizik
Tririg
Profile Design
ISM
Arundel
Solestar
Kogel
KMC
Karel’s Bike Fitting Process
Step 1
I'll discuss the information and videos from your bike fit form (completed online prior to the fit).
I'll perform a pre-fit assessment - understanding your physiology, movement patterns and range of motion as well as your athletic goals, past injuries and physical limitations.
I'll attach your bike to a direct drive trainer and watch you ride your bike in a variety of positions and at different efforts.
I’ll make any necessary immediate changes on the bike to ensure a smooth and effective bike fitting process.
Step 2
I'll place LED markers on several anatomical points on your body for the RETUL motion capture tool to follow. The RETUL measures you in 3D in real time and calculates the key angles of flexion and extension and body position, collecting close to 4000 body location sets per data capture in real time. The RETUL also gives me the ability to see inefficient movements that may increase the risk for injury or make it hard for you to gain fitness (and go faster/further).
Although the data is compiled on RETUL's 3D motion software, I am not stricly relying on this tool to give you a perfect bike fit. RETUL is just a tool. The RETUL system doesn't know what type of rider you are - your fitness level, physical limitations, strengths or experience.
Based on your feedback and what I see, we will go through a dynamic process of adjusting your posture and "fit" to achieve the best comfort, aerodynamics and/or performance.
Step 3
Throughout the fit, I will educate you and tell you what to expect, what to feel and what to work on to maintain the most effective positions on your bike. I always encourage questions and an open dialogue.
To optimize your fit, it's likely that several bike parts will need to be adjusted or replaced, such as (but not limited to): saddle, aerobar extensions, handlebars, crank size, arm cups. Typically, when you buy a new bike (or used bike) these parts are standardized and not ideal for your body height/size/fitness.
The average time for a bike fit is ~2-2.5 hours. I will never rush through a bike fit and I do not charge by the hour. My goal is to give you and your bike the attention it deserves.
Step 4
Based on my experience fitting countless athletes and fitness enthusiasts, I've come across a few common parts that may need to be addressed during your fit:
Crank arm size - Most bikes come with a standard crank size. There's a good chance you need shorter. Shorter cranks will let you ride in a more efficient position, be more aerodynamic and improve pedaling mechanics. The proper size will allow you to sustain strong power throughout the powerful part of the stroke.
Aerobars (for triathletes) - An aerobar extension will ensure proper arm angle and a neutral wrist position.
Saddle type - Saddle complaints are the most common issue that I address by helping athletes select the proper saddle, fixing the saddle in the right position on the bike and learning how to position yourself properly on the saddle. For triathletes, a saddle that is noseless with a split design will allow you to rotate your pelvis forward and to be positioned on it with the pubic rami bone (while riding in aerobars) so that you are not sitting on the sit bones.
Arm cups (for triathletes)- many bikes come with small, uncomfortable flat pieces to rest your arms in the aero position. In order to be able to ride comfortably in the aerobars, you will need to have larger, more ergonomic pads that will give you enough support and stability and will help you be able to rotate your shoulders while riding in the aerobars.
If you're interested in a bike fit, tune up or optimization, complete the form with a few details. We'll review your message and get back to you within 48 hours.
