What is the 3% rule for tires?
The 3% tire rule is a guideline for upsizing tires. It recommends keeping the new tire’s diameter within 3% of the original to avoid affecting performance and safety. A common guideline is the “105% Rule”: The external rim width should be at least 105% of the tire’s actual inflated width. This ensures that the rim controls airflow better than the tire, maintaining laminar flow. For example, if your 28mm tire inflates to 30mm, the rim should be at least 31.
What is the 105% tire rule?
The Rule of 105 states that for a wheel-tire system to be aerodynamic, the rim’s external width should be at least 105% of the tire’s measured width. In other words, the rim needs to be wider than the tire to reduce drag and improve airflow. The 3% tire rule is a guideline for upsizing tires. It recommends keeping the new tire’s diameter within 3% of the original to avoid affecting performance and safety.