Not necessarily. It depends on how close the tire is to the fender too. The more clearance to the fender you have the lower the car can sit. My Duster sits at 25" to the fender lip, and my 275/35/18's are 25.6" tall per the tire specs (the tread is also 10" wide!). The alignment makes a difference too, camber and caster can alter where the wheel sits enough to gain/lose clearance.
Much taller than 26" on the front tire starts to cause clearance problems with the front and rear corners of the wheel opening though, especially on a Duster because the wheel opening isn't as long as on a Dart/Demon. The 225/60/15's are ~25.6" tall, and you can see in my first picture above there isn't much clearance to the front or rear corners of the wheel opening. A 26" tall front tire on a Duster will probably require a little trimming of the front and rear corners, unless it's a pretty skinny tire that sits more inboard than usual.
He is not, and neither are you. I ran the 225/60/15's on my Duster without cutting or bending anything, and had no rubbing at all. The ONLY modification I made was to fully extend the lower fender to bumper brace to push the front lower corner of the fender out a little bit. But I made no changes to the brace or the fender in doing so, I just took advantage off all the stock adjustment available. I didn't cut the fenders, I didn't roll the fender lip or wheel opening, and I never had any rubbing. And I was driving the car every day, through pot holes, over speed bumps, you name it.
225/60/15's fit perfectly on my '74 Duster.
