FYI, I had an appointment with my insurance agent over lunch and asked him some questions related to offroading. This is with American Family Insurance, but you might want to check with your own agent. My questions and his answers.

1) Does modifying a vehicle suspension affect insurance?

Not as long as it's street legal.

2) Even if it is no longer similar in design to the original design, i.e. SAS?

This gets trickier. It's not a problem for liability only as long as it's still street legal. For Comprehensive and Collision he thought it would have to be inspected and evaluated for safety to see if they wanted to insure it.

3) Who determines street legal?

The state

4) Who determines if it's safe?

Don't know

5) Does add beefier bumpers and a winch affect my liability in an accident, i.e. if I T-bone a Honda and go right through it because my truck has a battering ram for a bumper?

Not as far as the insurance rate is concerned and the insurance would pay out to the maximum of my policy. He recommended a blanket liability umbrella insurance policy to cover my house and vehicles, for the case that I were sued for more than my policy allowed. $1 million for $175 a year.

6) Does insurance cover aftermarket parts?

Only if declared and they have a record of their value. The cost is $30 anually for every $1000 in additional coverage.

7) Does insurance cover damage incured offroading?

Yes, provided it isn't racing or other competition. However, prior damage will depreciate the value of the pay out in the event of an accident. For example, I have lots of dents all over that have never been fixed. If I get hit and smash a fender the panel will be depreciated for any existing damage before the accident occurred for calculating the pay out on the claim. If I wanted to fix all the dents they would be applied to the deductible individually since they occured during different incidents.