Adjusting the Seat
What kind of seat: Bikers who don't go off-road often prefer a wide seat -- particularly bikers who are placing a wide load on that seat. Real mountain bikers avoid wide-butt saddles, because the saddle won't slide readily forward between your thighs when you roll into an omygosh downhill. We also avoid gel seats, both because of the weight, and because these seats inhibit quick moves -- either side-to-side or forward-back -- of your butt on the saddle. Women will usually need a wider seat (insert your big-butt joke here), because the ischial tuberosities of the pelvic bone are more widely spaced. In general, rock bikers like the slimmest, slickest seat that will support them. The UtahMountainBiking on-line store sells several high-quality seats.
Getting started: I suggest you first set the seat height and fore-aft position to the "baseline". For a long and detailed series of instructions on fitting the bike to your body, see our bike-fitting page. This gives you a good starting position from which to make some of the tweaks discussed below.
Seat height: When the seat is higher, you're more efficient climbing, and it's easier to get up off the seat during a grunt climb. When it's lower, it's easier to rock back on those spooky downhills. Start with the seat at a height where your leg (with the foot horizontal, wearing your biking shoes and cleats) can't quite be completely straightened when you're sitting on the seat with the pedal fully down. (When you release the downward pressure, the knee should bend a bit, with the pedal still firmly under the foot.) This is usually the most efficient seat height for a long grind-it-out climb. For a rock-n-roll downhill, drop it down an inch or so.
Forward-backward position: The seat should be in a position where you can readily stand up. When you're on a slight incline, you should be able to rise off the seat without pulling or pushing on the handlebars to get yourself upright. If the seat is too far back, you'll find it hard to get your body forward to power yourself up a steep section, and hard to get your weight on the handlebars when riding up a tight switchback. Too far forward, and you can't ride a modest downhill while sitting. You may need to experiment a bit to find the position that gives you the best results.
Seat angle: The seat angle determines how much the seat contacts the front of your crotch, versus your butt. If the angle tilts forward too much, you tend to slide off the seat as you peddle. If the front tip of the seat aims upward, it puts pressure on the base of a male's scrotum during the ride. (The compression here can cause impotence -- which is incompatible with guy biker's image of "total stud.") Adjust the seat angle until you feel no pressure on your crotch, but don't slide forward off the seat as you ride. Normally, the horn of the seat should be just a tad higher than the back end when the bike is upright with both wheels on the ground. This gives you a bit of "longer leg" when you move forward to climb a steep uphill, and makes it a bit easier to slide backwards off the seat as you enter a steep downhill.
If you have a ratcheting angle adjustment (such as the red-trim seat shown in
the position-adjustment photo), loosen the bolt until the teeth of
the ball and socket come apart. Set to the new angle, then tighten down.