Tires are part of the suspension, that's why some bikes have huge donuts and some sport bikes a low profile. Talking about suspension, I remember the last time I rode a 12 year-old 400cc Steed the front end was scary, I could hardly make a turn at slow speed. It was okay at higher speed in a straight. Try this: stand over your bike, pull the front brake and pull up on the handle bars - the bike mentioned "grew" a few inches. When I let go, it "sank" back down. Probably nobody ever checked what's inside the fork tubes since it was new.
I didn't want to mess with the oil so I just cut two 2-inch PVC pipe pieces, opened the forks at the upper triple clamp, squeezed them in and closed the patient up again. The guy was far way from home, so this was quite an improvement, but I told him to check the springs and the oil when he's back home. That was part of the service you got in my Coffee Shop!
Interestingly it's difficult to get used replacement springs, at Red Baron they sell only the complete (used) fork set, which is of course expensive. Otherwise they would have lots of empty fork legs sitting aroud and no springs...