Time Trial (TT) Fit Calculator
Optimize Pad Stack & Reach for Aero Speed
Floor to crotch, firm pressure, shoes off.
Aero Pad Coordinates
Pad Stack (Y):
—
Pad Reach (X):
—
*Distance from BB center to top-center of arm pads.
TT Frame Recommendations
Recommended Frame Stack:
—
Recommended Frame Reach:
—
Position Specs
Saddle Height:
—
Ideal Seat Tube Angle:
—
The Time Trial (TT) Bike Fit Calculator is a digital tool designed to help you find the optimal riding position for a Time Trial or Triathlon bike.
📏 Precision Measurement Guide
- Inseam: Stand against a wall with a book between your legs. Pull the book up firmly (simulating saddle pressure) and measure from the floor to the top of the book.
- Total Height: Measure without shoes. Even 2cm of error can shift your Pad Reach by a full frame size.
⏱️ UCI Compliance Check Regulation
- Saddle Setback: Typically, the nose of the saddle must be 5cm behind the vertical plane of the bottom bracket (exceptions exist for height).
- Extension Tilt: Extensions and armrests cannot exceed an angle of 30° from the horizontal.
- Reach Limit: The horizontal distance between the BB and the end of the bars (excluding gear shifters) has strict limits based on rider height.
🚀 Aero Optimization Tips
- Crank Length: Consider shorter cranks (160mm – 165mm). This allows you to ride a lower stack without closing your hip angle at the top of the pedal stroke.
- “Mantis” Position: Tilting your armrests upward (10°-15°) can often close the “air gap” between your hands and your face, reducing drag.
- The “Shrug”: Once fitted, practice “shrugging” your shoulders and tucking your head into the “aero pocket” to hide from the wind.
Expert Insights & Common Queries
Power Production
“Why is my FTP 10-15% lower on my TT bike than my road bike?”
This is common due to hip angle closure. When you lean forward, your hip flexors are more compressed, making it harder for the glutes to fire.
Solution: Move the saddle forward and consider shorter (165mm) cranks to “open” the hip at the top of the stroke.
Solution: Move the saddle forward and consider shorter (165mm) cranks to “open” the hip at the top of the stroke.
Sizing Strategy
“Should I size down for a TT frame?”
Generally, yes. It is much easier to make a small frame “longer” or “taller” with spacers and longer stems than it is to get a large frame low enough. A smaller frame also offers a smaller frontal surface area to the wind.
Comfort
“I can’t hold the aero position for more than 10 minutes without neck pain. What’s wrong?”
You are likely trying to look “up” by craning your neck.
Solution: Practice the “Turtle”—shrug your shoulders to your ears and look through the top of your eyebrows. If pain persists, increase your Pad Stack by 10mm until your flexibility improves.
Solution: Practice the “Turtle”—shrug your shoulders to your ears and look through the top of your eyebrows. If pain persists, increase your Pad Stack by 10mm until your flexibility improves.
Aerodynamics
“Are high-hands (tilted pads) actually faster?”
For most riders, tilting the bars up 10-15 degrees is faster because it fills the air gap between your hands and your helmet, directing air around your torso rather than into your chest. It also stabilizes the upper body.