Which size chain do i need?
 

I have Panasonic DX 1000 road bike that needs a new chain. I was wondering which size and/or width i will need. Its a 12 speed. Thanks in advance.

Dérailleur chains of the width range of 7.8-7.3mm should work well. One of the problems with bikes is that the "size' that some parts are described by are not actual measured dimensions. So while all current dérailleur chains can be called 1/2"x3/32" in reality the ones for more gears are narrower then those for less gears. If you use a narrower chain then recommended it can get trapped between the front rings. Andy.

An 8-speed chain will also work perfectly for 6- and 7-speed bikes. I'm assuming that by 12-speed, your bike has six gears on the rear.

A 5-speed chain will be too wide to work properly. A 9-, 10, or 11-speed chain would be too narrow and could fall between the gears as Andrew mentions.

+1 You will see these chains listed as 8-speed or 7/8-speed or even 6/7/8-speed. All will work properly. Remember, that these newer chains must not be joined by reusing a standard pin. If you have to shorten it a bit you must always use the specific joining pin (Shimano) or master link (SRAM, Wipperman or KMC) provided by the manufacturer.