So, reckon you have a bike, and reckon you’d like to ride it.  Suppose, now, that you’re riding it, and you have horrible burning knee pain, or back pain, or shoulder/wrist pain.  It’s likely that your bike could use an adjustment!  I imagine this is a pretty common issue for new riders, as it was for me nearly a year ago, after I’d started riding my first bike in something like 10 years.  I bought a road bike with a very small frame, not really knowing anything about frame sizes, and the thing was set up for a small, middle-aged woman.  I am a hairy, long-torso’d man of average height, and riding it as it was caused me a great deal of discomfort, even reminding me, frequently, of a knee injury I’d sustained in 11th grade at a christian ska concert while I was skanking for Jesus.  Alas, I digress.

What I’m here to tell you today, friends and dear readers, is that you can take care of this problem yourself fairly easily!  I’m going to do my best to help you learn how to do it, but realize that this is a sort of blind leading the blind situation.  I’m a mere swaddling babe in the world of cycling, and it’s my hope that you take the following as more of a starting point, doing your own research to determine the best fits.  Good places to go for this information are Sheldon Brown’s website and YouTube.  Anyway, the first obvious culprit is your seat height, so let’s go ahead and start there.

There are just two spots to worry about, here:  your seat post and the bracket holding your seat – hereafter referred to as “saddle” - onto the seat post.  First, your seat post.  There’s a bolt that tightens the seatpost tube around it, and either it has a quick release or you need an allen wrench to loosen the bolt.  This part is pretty simple; if you don’t have a friend, you’ll kind of have to do it by feel, but your main goal if you’re just commuting or cruising for fun is to be comfortable.  So, basically, you’ll want your neck and your back relatively straight and upright, the amount of curve in your spine depending on the type of bike you have, and you want your leg to have a very slight, roughly 25 degree bend at the 6 o’clock position in the rotation.  Conventionally, you should have the bottom of your kneecap above the widest part of your foot on the pedal, but we’ll get to that.  Your first goal is to get that seat up high enough that your knee isn’t bent too far at the upper part of the rotation.  If it is, you’ll wind up putting way too much stress on the joint, which can cause an unnecessary amount of discomfort during and after your bike rides.  Be careful, though, as your seat post has a line on it indicated maximum height.  If this line is visible above the seat post tube, then you’ve raised it too high, and it could bend, or even break, making for a messy, possibly hilarious-for-others accident.  

This is how I currently have my bike setup, with my leg at full extension, at the 6 o’clock position:

I didn’t actually realize before I took this picture, but at this point in the pedal stroke, my knee is actually a bit forward of the ball of my foot.  Looking from above, I thought it was correct, which brings us to the next portion of this clearly very poor lesson:  Saddle adjustments!

There is a bolt that typically requires an allen wrench on the bottom of your saddle, where it attaches to the seat post.  Here, you can make adjustments to ensure your knee is properly positioned over your foot, and that you’re not bending too far forward over your handlebars.  It’s a pretty easy task; simply loosen the bolt and move your saddle forward or backward, and retighten.  If you have a full-length mirror, test the fit out in front of the mirror, checking your leg angle and where your knee sits over your foot at the bottom of the stroke.  

The angle of the saddle determines how upright you sit, and your main goal should be to sit comfortably without putting too much pressure on your wrists, elbows, and shoulder.  You should have a slight bend in your elbows when you ride, allowing them to behave like shock absorbers.  Otherwise, all the energy transferred from the road to your handlebars will go straight to your tender, soft bits, leaving you with sore wrists and shoulders.  I have this problem all the time because I’m too lazy to get longer brake cable housing and raise the bars.  This is my fault, and I accept full responsibility.  If you have the same problem, you can mitigate some of it by rotating your bars back.  I don’t do this, because I like riding in the drops, convinced that I look way cooler that way.  As illustrated by this blurry security camera snapshot, I don’t: 

But at least I got away with the loot.

As for bar adjustments, these are just as easy in most cases.  There will generally be two bolts you have to worry about – both requiring allen wrenches – one for bar angle, and one for height.  If you’re using the 7-shaped quill stem, raising or lowering the bars will also bring them closer or move them further away from you, respectively.  For comfort, a general rule that I’ve heard is that you want the top surface of your saddle to be flush with the top part of your bars, if you’re using regular drop bars.  This means that if you drew a straight line, parallel to the ground, from your seat to the bars, it would touch the top of your bars until they begin to curve downward.  Of course, not everyone has the same body type, and you may have weird ape arms or tiny t-rex arms.  In either case, you should fine-tune your bar height and angle to suit your freakish needs.  Your proportions are already humiliating; you may as well try not to add injury to insult.

In the end, you can save yourself a lot of hassle by getting a bike with a suitable frame size, but not everyone has the millions of dollars it costs to pay those fat cat professional bike fitters for their time, and then another dump truck full of dolla dolla bills to dump on a bike shop for a brand new Masi, so if you end up with a used bike that doesn’t quite fit, but is pretty close, know that you have plenty of wiggle room, so stop panicking.