Before replacing the wheels, when was the last time you replaced the blade or had it sharpened? yes, wheels could cause a problem, but you needvto check other things first.
I sharpened the blade a couple weeks ago. I usually sharpen and balance it a couple times per season and am very careful not to hit rocks, sticks etc. I take really good care of all my power equipment, wash it after every use etc. The mower is absolutely MINT. LOL.
The blade looks like it still has plenty if meat on it...when I do sharpen it, it takes very little to give it a nice edge.
Ill be honest, I acquired the mower in 2002 from my Grandfather when he passed and I've yet to replace the blade.
Probably time for a new one? Lol.
I've never really thought I needed to replace it because like I said, I've never hit anything, always kept a nice edge and up until recently, it's cut beautifully.
Now that I think about it though, this is the first season I cut it on maximum height, previous seasons I'd cut second or third setting from max height and this is the first season it hasn't cut corrrctly.
Maybe I'll pick up a new blade but try next cut with current blade on a lower setting just to see how it cuts before I change it out.