Airbus 320
 

Last night I happened to see Indian Airlines AIRBUS 320 with Four wheels on each main landing gear where as the Gulf Air had TWO why was this:confused:

Gear Layout is optional with the 320. Either 2 or 4 each. There are also A320 with different MTOW, although I believe this is a matter of certification rather that structural.

IC Airbus 320
 

Indian Airlines had all 320's modified to a four wheel config. This was because the aircrafts were aquired when most of the fields operated to were less than 6000' and required special ops. as per the 320 manual. A 4 wheel config has a better braking ability.:D

Here's a picture of an Indian Airlines A320 with 4 wheeled bogies

Only Indian Airlines has taken the option so far. It does weigh and cost a bit so no-one will take it unless they really need it but at least it is there if an operator does have a real need.