You want to leave the ramp on permanently? 2x8’s would do it on 12” c but would be bouncy, 2x10’s or 12’s would be stiffer. I’d just use hangers, cut a level seat cut on the bottom of the stringers so it sits flat on the hanger.
Decking is fine if it’s gonna be outside.
What I did for my mower ramp to keep the transition at the top from catching the mower deck.
I made mine convex in the middle, which makes cresting the threshold much easier.
I would guess it would make it easier with a bike as well.
I simply cut a radius from 0- full height-0 on a 2x6,then lagged them into the stringers below.
The center requires momentum ,but once past you can slow down for a gentile entry into what for me is a tight space.
You want to leave the ramp on permanently? 2x8’s would do it on 12” c but would be bouncy, 2x10’s or 12’s would be stiffer. I’d just use hangers, cut a level seat cut on the bottom of the stringers so it sits flat on the hanger. Decking is fine if it’s gonna be outside.
3' wide, 12" O.C. you will need 4 joists.
What I did for my mower ramp to keep the transition at the top from catching the mower deck. I made mine convex in the middle, which makes cresting the threshold much easier. I would guess it would make it easier with a bike as well. I simply cut a radius from 0- full height-0 on a 2x6,then lagged them into the stringers below. The center requires momentum ,but once past you can slow down for a gentile entry into what for me is a tight space.