The calibration and repair methods for the main bicycle components introduced here are primarily simple and effective emergency solutions used by athletes during training away from their base, where full bike repair machinery and tools are not available.
I. Frame Calibration
When a bicycle is hit head-on, the top tube and the front end of the down tube may bend upward. To correct this, remove the handlebars, fork, and the upper and lower cups of the head tube. Insert a steel pipe with a diameter slightly smaller than 30 mm into the head tube, then insert one end of the pipe into a wall hole or clamp it in a bench vise or a specially designed wooden post. Hold the chainstays and seatstays with both hands, using the head tube as a fixed point, and pull the frame in the direction indicated by the arrows in the diagram. Avoid excessive movement each time, constantly check the correction progress, and continue until the frame is properly aligned.
Another simple method is to wrap a steel wire, sturdy rope, or nylon cord around a large tree, forming loops at both ends that fit over the axle ends. Secure the loops with the axle nuts or tie the rope directly to the connection between the fork and the axle. Then, holding the handlebars with one hand and the saddle with the other (preferably with two people), push the bike forward to loosen the rope, then pull backward forcefully to use the momentum to correct the deformation. If it’s not corrected on the first try, repeat the process once or more, checking the alignment frequently. Avoid using too much force to prevent reverse deformation.
If a head-on collision occurs during training and the fork legs bend backward or the front and down tubes’ front ends bend upward, making the bike unrideable—and no tools or ropes are readily available—a makeshift solution can be used. Turn the bike upside down so the saddle and handlebars touch the ground, position the bike upright, have one person sit between the rear wheel and the crank to hold the bike down while pressing their shoulder against the front wheel and pushing it forward, while another person presses down on the rear chainstays to assist. This helps restore the fork and the top and down tubes to their original shape.
II. Chainstay and Seatstay Calibration
After a side impact, the left and right chainstays and seatstays may become asymmetrical, with one or both sides leaning outward or inward. This affects the bike’s forward propulsion, reduces speed, interferes with gear shifting, and may even cause the chain to fall off. To check, remove the frame and lift the front part so the chainstays’ ends rest on the ground. Looking from the right side of the head tube and seat tube, observe whether the distance from the right side of the head/seat tube to the right side of the chainstay ends (AB) is equal to the distance from the left side of the head/seat tube to the left side of the chainstay ends (CD). If AB does not equal CD, the stays are deformed.
Correction Method: Lay the frame flat on the ground and step on the chainstays and seatstays that are closer to the ground (step as close to the bottom bracket as possible). If the upper stays lean outward (larger AB distance), press them downward; if they lean inward, pry them upward. Then flip the frame 180 degrees and use the same method to correct the other side. The corrected frame should have AB equal to CD.
III. Handlebar Calibration
The most common handlebar deformation is when the crossbar is uneven, causing the grips to be at different heights or at unequal distances from the stem—either closer in or farther out on one side. To fix an uneven crossbar, insert a steel or wooden rod under the lower side and press down on the higher side. Hold the rod’s end A and pry upward or grip end B and press downward to correct the alignment.
If the grips tilt inward or outward, lay the bike on its side, step on the grip near the crossbar on the grounded side, and pry the other grip upward (or press it downward). Repeat the same method for the other side if needed.
IV. Fork Calibration
Common fork deformations include three types: a bent steerer tube, front fork legs being misaligned front-to-back, or misaligned inward-to-outward. To correct a bent steerer tube, clamp the bent section in a bench vise or wall hole, insert a steel rod into the steerer’s sleeve, hold the rod’s other end with both hands, and pry upward if the bend is downward or downward if the bend is upward. Avoid using excessive force. To check if the fork legs are misaligned front-to-back, place the upper ends of both fork legs (near the fork crown) on the edge of a flat table so the fork tips touch the surface. If both tips touch the table evenly, the legs are not deformed; if only one touches, they are misaligned.
To correct misaligned fork legs: if one leg has too much tilt, clamp the fork as shown in Figure 25, grip the fork tip, and pry in the opposite direction of the bend. If the tilt is too slight, pry in the direction of the bend until both legs have the same angle.
To check if the fork legs are misaligned inward-to-outward: visually align the extended centerline of the steerer tube with both legs—if the distances AB and BC are unequal, the legs are misaligned. To correct, place the deformed leg on the ground and step on the fork crown area. If the upper leg bends inward, pry it upward; if outward, press it downward. Flip the fork so the previously grounded leg is upward and correct the other leg the same way. Alternatively, clamp the fork in a vise and pry the legs to correct the deformation.
The corrected fork must have AB equal to BC, and the distance between the fork tips should fit the front wheel rim—typically around 95 mm.
V. Rim Deformation and Correction
Deformation of the rim caused by broken or loose spokes usually results in axial runout (side-to-side wobble) and radial runout (up-and-down wobble). For minor deformation, adjustments can be made while the wheel is on the bike. For more severe cases, remove the wheel and tire, and place the rim on a truing stand. To fix axial runout: first adjust the bearing alignment, tighten the fixing bolts, identify the range and extent of the axial wobble, and mark the affected area on the rim or tire. If the rim wobbles to the right, slightly loosen overly tight spokes on the right side of the rim and tighten those on the left side that are too loose. Reverse the process if the wobble is to the left.
To fix radial runout: first address inward runout by alternately loosening overly tight spokes on both sides of the affected section. Then address outward runout by alternately tightening overly loose spokes. If the rim still wobbles, adjust the tension of spokes near the affected area in addition to those in the wobble zone.
Truing a rim is a delicate task. Each spoke nipple should be turned in small increments—generally no more than a quarter to a half turn at a time. The goal is to reduce the overall rim runout to less than one millimeter.
Severe twisting or "dead bends" in the rim caused by collisions or falls during training cannot always be corrected by adjusting spoke tension. In such cases, remove the rim, tire, and spokes (or some of them), and use a wooden stick or hammer to gently tap the rim back into shape (place a piece of wood under the hammer to avoid damaging the rim). For major twists, lay the rim on the ground and press it flat with your feet. You can also use a lever to shorten the rim’s long axis or lengthen the short axis. Then draw a circle with a 670 mm diameter on the ground to check alignment. If the rim largely overlaps the drawn circle, the oval deformation is eliminated. Reinstall the spokes and use the truing stand for final precision adjustments.