how high is mowing high?

Just came into a house with a very weed ridden lawn that I have been mowing with the mower at 4".  It looks like mostly KBG with some other varieties mixed in. 

I want to see if I can crowd out the weed growth over the next year (or more), but I'm a little concerned about the grass getting matted if it's going to be growing more than 4."  The blades look as though they're tipping over a bit and some of the edges have actually gotten a little matter already.

Should I cut at 3-1/2' or is it okay to continue mowing at 4"?

Thanks.

If the grass isn't getting cut at all, then you might need to lower it.  It's true that KBG doesn't always stand tall (like Tall Fescue), but I think that 4" should still be cuttable.  Perhaps it's feeling a little thirsty?

Thanks, Jeremy.  I gave it another cut recently at 4" and it looks okay.  Methinks in an effort to let it grow long and shade out weeds, I was letting it go too often between mowing.  That probably contributed to the blades falling over.

I've had this lawn for all of three months, so I am still getting the hang of it.

Thanks again.

I've noticed that when I cut all the way up at 4", I have to mow VERY regularly or the mower pushes the blades over and I get a very uneven cut.  On my mower, I mow one notch down from 4" now, and it's a bit more forgiving in terms of being a day or two late with a mow.