What a Bicycle Assembly Mechanic May Encounter
Not all new bicycles are perfect out of the box. In fact, manufacture defects can happen. It is part of the BAM certified bicycle assemblers job to inspect bicycles and spot these issues.
The cracked head-tube revealed when the BAM inspects the bicycle.
A great example is a cracked head tube. In this article we will show you why it is important to inspect bicycles.
Frame cracks are not always easily found. When you first remove the bicycle out of the box, remove the seat tube and install. Then mount the bicycle of the service stand on the seat post and not the frame. This is known as the second best mounting position. The reason for this is that at this point your bicycle is still wrapped and the seat tube is not easily accessible.
Closely examine the frame for cracks. Look for imperfections in the paint finishes. Common locations for issues will be at the weld connections for both alloy and steel frames. These are found at the connection points of the head tube, bottom bracket and stays. Other locations are at the contact point where any race pressing as been conducted. These are the head tube and bottom bracket.
In this example we located a 25mm crack located at the bottom of the head-tube. This crack was very evident. Easily seen is a full crack through paint finish.
Image shows a crack visible thought the head-tube right out of the carton. Is this just a paint scratch?
Is this frame repairable?
The easy and quick answer: No. Frames under riding load constantly come under strain when flexing. The points under the most stress are the bottom bracket and head tube. If you were to TIG weld the crack that is found on this frame there is no way to guarantee its reliability under riding stresses.
It is the responsibility of the Bicycle Assembly Mechanic to inspect the bicycle and assemble to specifications for public and cyclist safety.
Brian Hahn is a fully certified professional bicycle mechanic, a former member of the PBMA and an instructor of CABS. He has been published in several publications on varied topics. Over the past six years he has taught both the BAM Certification program and the Bicycle Building and Wheel Truing Certificate courses. You can also connect with him on our Workshops throughout the year.