Some of the Schwinns are hybrids that can be converted with road drop bars or can be made more like an mtb using wider "29er" tires.
I found this 2008 Schwinn Broadway at goodwill for $40 in neglected condition, so decided to make it more of an off-roading bike since it had a suspension fork that was super-easy to rebuild.
Adding the rubber gaiters/boots to the fork legs while I had it apart keeps the exposed grease on the fork tubes from attraction dirt and thus allowing the fork to become contaminated inside with the fork action becoming sticky again.
The original wiper seals on these X-mart forks don't do their job when it comes to keeping the grease in and keeping the dirt out!
I shortened all of the too-long old cabling, trimming off the bent housing ends and greasing the wires to restore smooth shifting and braking action. I also replaced the rusted chain with a new Shimano HG70 chain that has bulged side plates for more positive shifting under load.
The wider 29er tires fit right on, but make adjusting the brake pads rather tricky since the original rims are so narrow.
I changed the rack to a more compact style, and with the weight of the bag on it with an extra water bottle inside, this really helps off-road climbing traction.
So here is the before-to-after photos of what is a poor-man's 29er mtb: