is 25kg.cm stall torque is good for that???
Each motor, assuming a perfectly balanced load, will need to haul away 27.5kg.
If your wheels are 1 cm in radius (2cm in diameter), you'll need more than 27.5kgf-cm of stall - around double that, say 50kgf-cm of stall, would be good. Stall is when it can just hold the force, but cannot move.
If your wheels are 5cm in radius (10cm in diameter) you'll need 5 times that, or around 250kgf-cm.
3 times larger wheels equal 3 times more torque needed and so forth.
i dont know how can i choose motor torque.
Reading a few tutorials (link on top of the page, right side or Google the subject) on the subject might be a good start.