Isaac Bicycles has issued a voluntary service recall pertaining to all of its full carbon forks and expander plugs built since 2004, but stresses that there is no physical defect in either the design or manufacture of the components themselves.
Rather, the recall notice emphasizes the need to exercise proper care in both the assembly and maintenance of related parts and the new 60mm-long replacement expander plug is required only to increase the margin of error, not to bring the system up to a minimum safety standard.
The service bulletin represents the company’s view of ‘best practice’ for carbon steerers and outlines several precautionary and/or corrective measures. According to Isaac International’s Dave Palk, none is individually more critical than the others though all are related to how the internal bore of the stem interacts with the steerer tube surface:
1.The lower collar of any stem used on an Isaac carbon steerer tube must be 7mm tall or more. Shallower stem collars may indent the steerer tube surface and create a dangerous stress riser even if the steerer tube clamp bolts are properly torqued.
2. Headset spacer height below the stem must be limited to no more than 30mm but should be at least 5mm. Exceeding that figure will create too long of a lever arm on the steerer tube while running no spacers at all will create undue point stress at the base of the stem. In addition, the steerer tube length should be cut such that it just slightly extends completely through the stem for maximum surface area contact.
3. All Isaac steerer tube expander plugs should be replaced with the new 60mm-tall version, which will be provided free of charge and offer additional reinforcement below the bottom edge of the stem as a redundant safety precaution. To ensure the plug extends to the correct region of the steerer tube, total stem clamp height should be no more than 45mm and a maximum of 5mm of spacer should be placed on top of the stem.
Again, Isaac Bicycles is keen to point out that this recall does not involve any defective or faulty Isaac components but only pertains to the “potential for damage due to incompatibility and misuse.” Though other manufacturers may not have issued such specific guidelines, Isaac’s conservative view of what should be used on its own bicycles are sensible rules of thumb that can also be applied to other makes as a precaution.
For more information, visit www.isaac-carbon.info.