It seems like an obvious statement but rubbing on a bike is never good, unless of course you're in a race and rubbing the contestant next to you to get an edge. For the most part the only rub encountered is the chafing on our own undercarriage and quite frequently the brake pads. When brake pads rub on the fork of the bike it not only makes an annoying sound and wears down one pad faster, it creates a jerking motion that can make the bike much harder to navigate. The sooner we fix this mountain bike v-brake rub, the more enjoyable the ride becomes.
Step One: Loosen the Tire
To perform the process of elimination we must first make sure that the brake is causing the rub, and not a tire that is off centered or out of true. Release the skewer near the bottom of the front fork and make sure the tire is balanced and center. Now tighten the tire back up and see if the rubbing issues remain. If they do it's time to adjust the brakes themselves.
Adjust the Brake Centering
If the tire is centered but you're still experiencing a rub, you must adjust the brakes. Near the bottom of the front brakes are two little screws. You can center the brakes by tightening the screw on the non-rubbing side a half-turn while loosening the opposite one the same amount. Try the brakes and if there is still rub it may take some adjusting back and forth until the v-brakes align nicely.
It's important to monitor your v-brake every so often and possibly even keep a small screwdriver in your ride-along toolkit so you can adjust while out on a ride. Save the rub for the pork at your next barbecue.