I remember when I first started riding mountain bikes. It was the late 80's and things were evolving rather quickly. Drawing on ideas from bicycles, motorcycles and industrial machining, a flood of ideas was building that would be big enough to bury us all. Being a shop rat and ready to embrace all things new was a bad idea. I adorned my Yo Eddy with gaudily colored, overly-machined parts complete with way too long and low stem and chopped down handlebars. There was barely enough room to fit brake levers, shifters and grips before the bend. I rode like this for years thinking it was a good idea.
Then came riser bars. And good suspension. And finally comfort.
Finally it's totally acceptable to ride with your handlebars the same height as your saddle. No more granny comments.
So what has happened out there in the world in the last 20+ years. Did we get smarter. Are dudes my age spec-ing all of the bikes out in the world. I know there are actually people who still ride with long stems and chopped off bars in their stretched out neon lycra. But most of the world is starting to embrace proper bike fit and comfort.
Let's face it, most of the world is not out to be a world champion. They just want to be outside having an enjoyable experience on the bike. And this goes for road or mountain rider alike. The key to enjoyable cycling and the road to improvement, begins with proper bike fit. The more dialed you are on your bike, the longer and faster you can ride. Or you can make that trip to the corner store in half the time in an emergency.
Look at almost any video footage of Eddy Merckx, the great one, and I'll guarantee you he measures and adjusts something on his bike. He was fanatical about bike fit, and it apparently paid off. He looks pretty comfortable blowing peoples doors off.
So what do you look for in proper bike set-up?
Well first of all, because of mountain bike suspension, we have to differentiate fit and suspension set-up. Both are very important, yet independent of each other. First you have to get comfortable on that mountain bike before you start turning knobs and dials.
Now this is by no means a formula to get the perfect fit on your bike. On the contrary, it's more of a "what to look for" and when to seek a professional.
There are three areas of contact on the bicycle. Your hands, feet and your arse. The magic triangle. Get the angles your body draws correct, and you'll be a happy camper on your rig. Get them wrong and you will likely struggle.
Your cockpit length is most important. This begins by having the right size bike with a top-tube that is close to the right size. An important part of the saddle-bar reach. Saddles can slide for an aft, moving your rear wheel weight and knee angle. Ideally you want the ball of your foot over the pedal spindle. You can usually tell if your saddle is in the wrong spot if you are always favoring the nose or tail. The stem length and angle affect where your bars are going to sit. Racers (road or mountain) go long and low for climbing and overall power. This is great if you want to go fast, but handling will be sacrificed on the downhill. Thus, down-hillers run their bars high and short, with wide bars for leverage. They want a heads up riding position with quick steering feedback. Set your bike up like this and you will hate the way it climbs, at least at first. Somewhere in between these two is a compromise. You also have to decide which ride quality is most important.
Keep in mind though, if you really want your bike set up like a rocket ship, your neck or back may hurt at some point. And you can't get pissed if your downhill chopper climbs like it has two flat tires and you can't hold a straight line. Big adjustments one way or the other will yield that compromise. Little adjustments however will get you somewhere in the middle. Just remember a few millimeters one way or another can yield a result, and you only want to adjust one thing at a time.
Once you get your fore-aft position dialed in, you need too figure out the pedal-saddle height. A good starting point is having a slight bend in your knee on the full downward position. Too high and you will rock on the saddle and jack up your hips and knees. Too low and you will strain your quads and tops of your knees. The more dialed your seat height, the more efficient you are.
Now about that suspension set-up. The ideal situation is to befriend a good mechanic who does the work on your bike. Ask them what and how many adjustments your shocks have. The front and rear shock should work together. Too much/too little in either one will affect how the bike rides. The set up chart that comes in your owners manual is a great place to start. Many manufacturers also include the shock manuals for higher end bikes. Find out what adjustments you have. Are your shocks air or coil spring. Air and all you will need for adjustment is a pump, coil and you could be looking at different springs to achieve the ride you want. Rebound, compression and lock-out are options on nicer shocks. Compression is how fast your shock squishes down. Rebound is how fast it returns. This is achieved by opening or closing oil flow. Open, the oil runs fast, and as it closes the oil becomes more impeded. Adjusting these two can make your bike feel like a pogo stick or a bucking bronco. As with making fit adjustments, make very small adjustment when dialing in suspension. One or two clicks at a time. You should definitely notice a difference in one and three clicks, oil flow will be slower or faster. The rule of thumb is a smooth compression a rebound between "snappy" and "slurpy." This will make more sense when you push on your shocks.
Bike fit and suspension set-up are way more than I could ever begin to cover in one sitting. This is just some general platforms. I will try to edit this so that it remains a concise overview.
Getting comfortable on a bike takes time. There are a great deal of factors that contribute to positive or negative outcome. Do yourself a favor and spend the time getting to know your bike and how it's set up. It will make you dig riding that much more.