Do not use tire levers or any tools to install the tire - try to just use your hands. As mentioned above, it's not about strength and force, but technique. I've installed some pretty tight road tires (700x23) without tools, and I ain't considered strong. Also realize some tire / rim combinations could be harder to mount than others. For example, I find Continental Gatorskins to be very hard to mount but Specialized Armadillo Elite All Condition are much easier on the same rim. Regardless, I can install both without tools.

1. This video shows the trick of using the depression in the middle of your rim to your advantage. When approaching the last bit of unseated bead,pinch your tire into trough of your rim.:

https://www.youtube.com/watch?v=Wulx...ature=youtu.be

2. I like to start on the tire opposite the valve stem, and the last mounting section is the valve stem. And when I pinch my tire, I like to use both hands, start pinching and dragging my pinched fingers around the rim (each hand moving in opposite direction towards the valve stem. This ensure the entire bead is in the trough, giving you as much slack as possible, then attack the last bit with relative ease.

3. Also, it may help to warm up the tire (say in the sun) to make it more pliable.