Question: I just purchased a used tandem from a family friend. The tandem bike is a bit old, has seen its better days, and I am unsure of my next step. What is your advise for someone who has just purchased a used tandem?
Answer: Used tandems present a unique opportunity for tandem teams to enter into the sport on a tighter budget. Buying second hand allows you to dable without fully committing and depending on the tandem purchased may be a great way to get a very nice tandem bike on the cheap. The downside is that purchasing a used tandem presents an entirely new set of early risks not found in buying or building a new tandem.
When purchasing a used tandem your inspection should begin at the frame level. Depending upon age, frame design, and material used there are a number of points of contact to inspect for signs of premature wear, previous damage and repairs, and signs of neglect. Generally speaking tandems are manufactured using the standard materials of the day; steel on pre-1990 frames, aluminum on post-1990 frames, and carbon fiber on more recent road tandem frames. Each material has its advantages and disadvantages, beyond the scope of this answer, so perform some web searches for “signs of fatigue on xyz material” to learn more about what to look for. In your cursory review look for weld cracks, gouged tubing, or signs of early fatigue.
If the frame checks out next move on to the components. Tandem bikes are generally assembled using heavier duty single bike parts. While suitable for use on tandems these parts are not designed or certified for use on a tandem. In your inspection start with the parts that can cause catastrophic failures:
Overall you are looking for signs of neglect or abuse. A tandem is designed to handle the weight and torsional forces delivered by two riders but the components, generally, are not. Should you be unsure of how to inspect any of the parts above then do take the bike to a qualified shop for inspection. If there is any doubt about the status of a component part now is the time to replace it.
If everything checks out a this point do plan on replacing the following components/ parts no matter what:
Assuming everything has checked out, been replaced, and the used tandem is in your hands take care on your first few rides to not push the new tandem to the limits. View the first few trips as a breakin period for both your tandem team and the tandem bike. Get to know the characteristics and handling traits of the rig. Pay close attention to the frame and components for any signs that you may have missed in previous inspections.
As your comfort level increases with your ability to handle the new bike and with the condition and quality of the tandem begin to up the intensity of your rides and enjoy the fun of a tandem bike.