stapfam

How heavy are you? For offroad- the standard fitted tyre used to be 1.95. This was good for an average rider of average weight.

Now a narrower tyre will require more pressure to stop pinch flats- called snake bites by the way- but will roll better on all surfaces. I mean all surfaces-Tarmac- hardpack- gravel- MUD. The only thing you will lose out on is a bit of Suspension and comfort and Grip across wet rock and tree roots. They take skill to negotiate aswell so wide tyres do not always help here either. I weigh 150lbs and I use 1.8 tyres (Fire XC's) My mate weighs 180lbs and he uses 1.95's Our Tandem all up weight is 400 lbs and we use 2.1's.

People and "Poseurs" think that a wide tyre is cool and works better. You want grip and speed-go narrow. I even use Continental Cross Country 1.5's in winter for extra grip on the gloopy surfaces. A narrow tyre cuts through the gloop to the solid surface below and gives me grip. A wide tyre will float across the surface and not get grip. The only way to get grip on a wide tyre is to run at a lower pressure so causing drag and the chance of snakebites.

Now if you are talking about Trials riding then all the rules go out of the window. Wide tyres- low pressures and lots of riding skill. For general riding- then narrow rules- within reason but Depends on your weight and what sort of riding you do.