I've been told that running more air in the front tires and setting the front shocks at there lowest setting will give me a better ride over ruff terrain and better handling(turning), my question is will putting 8 or 9 pounds of air in the front make the tires prone to failure. I have a 07 400. Thanks for the imput.---MIke

 

I ride with 8lbs of air in the fronts because the stock tires (06 400 w/Carlisle Badlands) with only 5 lbs of air have a tendancy to come off the rim on ruts or if you winch on an angel. I found 8 lbs to give better control and easier to get over objects.

 

I run 8lbs in the front and 5lbs in the rear. I did that with my OEM tires and now do the same with my 6ply tires. I run the front preloads on the softest and the rears seem to work best in the middle setting (with the OEM tires the rears worked best on second to the softest). I don't get any 'roll-under' in hard turns or in off-camber situation. It steers easier too. It improves the handling by taking some of the oversteer out. (tippy and like you are going over the handlebars in corners, or do a nose-dive over the outside front tire)
One way to tell is to try it and see for yourself.

 

I tried 7lbs of air in the front and 5 in the rear. The shocks in front are on their softest setting, the back on the next softest setting. With the additional air it seemed when I hit anything with the front it seemed to more of a jaring effect then with the 5lbs of air in them. It maybe just me.--Mike

 

More pressure means fewer bumps are absorbed by the tires. What do you want, better turning or a softer ride?

 

<div class="FTQUOTE"><begin quote>Originally posted by: thundercat

I tried 7lbs of air in the front and 5 in the rear. The shocks in front are on their softest setting, the back on the next softest setting. With the additional air it seemed when I hit anything with the front it seemed to more of a jaring effect then with the 5lbs of air in them. It maybe just me.--Mike</end quote></div>

Gee Mike, I don't know what to tell you. With 8lbs in the front mine just cruises over little bumps (like tree roots growing across a trail 1" or so), like they aren't even there.
You just have to keep changing settings until you get things the way that you like it.
For giggles I turned my rear preloads down to the softest - man I had a hard time keeping it on a dirt road - all squirley like I had a flat tire in the rear.
Keep messing with it eventually you will find a combination that works for you.