The second function of tires is shock absorption. The bigger the tire the better it will absorb the bumps in the road or trail. For most roadies a 23 or 25 are ideal. It’s small enough that it is still light and has little rolling resistance and with the right tire pressure will absorb most bumps in the road. What the right tire pressure? It depends a lot on the rider’s weight. For most riders 100- 120 psi will be perfect. I like to roll about 5 PSI less in my front.

On the trail. If you have a good suspension fork you may be able to get away with a narrower tire. About a 2.0 inch. On a rigid MTB go with the biggest tire you can fit in your frame. Tire pressure will vary depending on trail conditions. On a hard packed trail you will probably be good with 35-40 PSI. on a rougher technical trail with lots of rocks you may want to try closer to 30 psi. Think about going tubeless! Tubeless allows you to run lower tire pressure without the threat of pinch flats.