I'm thinking of adding suspension forks to a rigid mtb. I realized that the geometry will change with the front higher and so the chain will be slanted up. Does this affect how hard and tiring is it to pedal and the steering. If I were to do it, how much travel of suspension do I need, or should I just stick to the rigid.
You can most likely switch to suspension forks without much trouble at all. The shouldn't be any real difference in how hard it is to pedal as you're still putting in the same amount of energy with the same number of turns of the cranks. The only thing i would suggest is to Stick with the Smaller Travel Forks as that will minimize the amount of difference that you notice in how the bike handles.