The one thing all tandems have in common is that they utilize a lot of moving parts. With the additional moving parts comes additional sources of annoying creaks, cracks, and strange noises. The primary cause of unwanted noise on a tandem bike is movement between two solid metal parts.
During installation or the building process of a tandem frame the mechanic will apply grease between adjoining parts. Over time as a result of wear, grit, or water this grease will be removed allowing the parts to touch directly. This touching is the source of 99% of all strange noises from the tandem.
To eliminate strange noises it should be obvious that simply applying grease to the areas where it has washed away will solve the problem. Unfortunately finding that one source of missing grease can be quite trying. To help troubleshoot the potential sources we provide the following list of potential culprits in order of likeliness:
The best method for identifying the source of the noise is to use the above list while the tandem is in a stationary position and listen for the noise emanating from the part. For example, place the tandem securely in a stand and pedal the cranks as you listen closely to the bottom bracket. If the noise is coming from there remove and grease the area. If the noise is not coming from there move on to the chain rings. Working your way down the list should eventually sort out the source and quiet that noise.