tip from my side book tkt form coimbatore not from tirupur change bp as tirupur kerala exp,
its upto pax to book a tkt alternates will avl every time .
No use to change boarding point as Tiruppur, because same quota for both Tiruppur and Coimbatore, I know this trick and is useless. So only to go to Nizamuddin from Erode I opt for Erode to Saharanpur Quota in 12687. This Saharanpur Quota may surprise you with up gradation, but not the NZM quota, because 80% train gets vacant at Nizamuddin.