how to determine which object to sit on?

I am making a game where the user has to catch a bicycle and then he can ride on it. But I am confused! The Humanoid.SeatingPart isn't writable and as expected, the player is tripping. What to do? Below is my code.

local bike = game.Workspace.bicycle

local function onPartTouched(otherPart)
    local character=otherPart.Parent
    local humanoid=character:FindFirstChildWhichIsA("Humanoid")
    if humanoid then
        humanoid.Sit=true
    end
end
bike.Touched:Connect(onPartTouched)

Is there no other way than to make a seat part?