My max ran very quiet on highway before. But now the tire noise is very loud. The only thing I did is over-inflating the tire to 42 psi, and now I change back to 32 psi. (my front tire treads are low)

WHat could be the reason? shock? tire pressure? low tread?

 

when tire tread decreases road noise increases!!!
and never overinflate your tire past the max pressure on the sidewall will cause tire wear in the middle of the tread pattern while the outides are still thick oh and you might want to have your alignment done all 4 wheels not just front the maxima is adjustable all the way around and they eat tires when they are out of alignment!
Goodluck!

 

You might want to check on the bearings to...they can make a noise if there worn out...usually u only hear the noise after u get going fast enough.