Choosing the correct frame size is a crucial component of getting the most out of your road bike. It's not just about comfort: when a road bike fits properly, it's more efficient, easier to handle, and better at transferring your power to the road.
Fine-tune your fit
Now that you've identified the frame size that fits your dimensions, a Trek retailer can fine-tune your fit with small adjustments and helpful accessories. These adjustments will be related to the bike's geometry, so understanding the following elements of road bike geometry will help you find the perfect fit for the way you ride.
Standover height is the distance between the ground and the top of the top tube. It's important to have a bit of clearance between you and the top tube in order to easily dismount the bike and comfortably place your feet on the ground when necessary. To ensure proper standover clearance, make sure your inseam measurement fits the frame size of your bike.
Reach describes the horizontal distance from the center of the bottom bracket to the center of the head tube, and is not affected by seat tube angle. A longer reach will result in a more streched out position, while a shorter reach allows the rider to sit more upright. Handlebar reach can be adjusted by swapping the bike's stem.
Stack is the vertical distance between the center of the bottom bracket and the center of the head tube. It indicates how tall the front of the frame is. Taller stack provides a more relaxed pedaling position, while shorter stack allows flexible riders to get low and aero. Headset spacers are the easiest way to adjust stack.