Essential Knowledge Guide

Setting Up Your MTB
Adjusting Seat Post Height

Okay, we begin with seat post height.  There is a definite range of motion where your knee joint is simply rotating into line and your leg isn't extending.  This motion applies no power to your down stroke on the pedal.  When setting your seat post height, raise your seat as high as possible, while not entering this range of wasted motion. 

Put on your normal ride gear.  Get on your bike and ride around a little to get into your normal riding position.   Come coasting back to a convenient wall or tree and park a handlebar end against it, and stay on the bike.   Don't move your rear!  Now, back pedal until you have the crank arms pointing straight up and down (this is difficult to tell from your point of view, ask a friend if you need to).  Do not lean over to the side with the crank arm down.  Stay sitting in your riding position, hips level. 

You should have a small bend in your knee.  If you have a large bend in your knee, raise your post about a half inch and try again.  If you have to stretch or lean to finish your down stroke, lower your post a half inch and start again.  To get just the right bend, place the heel of your lower foot directly on the pedal.  Now extend your leg fully. If you have to stand off the seat, you need to raise your post.  What we are actually setting here is your Maximum Effective Power Stroke.

To move your post, find the clamp at the point where the post goes into the frame.  It will be secured by one or two bolts, or a quick release lever.  While holding the post, loosen whichever mechanism you have, just enough to allow the post to move.  If you loosen too much, the post will likely just fall down into the frame if you let go, and you'll have to start over.  Make your adjustment and tighten the clamp. 

If your post was previously too low, you will feel a dramatic increase in pedal power!  If your seat was too high, you will mainly become more stable on your bike, but you will now also be able to learn to spin.  Tweak the seat post height a few times by going riding for ten minutes or so and making finer adjustments. 

Once you get a seat post height set, make a mark on the back of your post.  Most people should do this because they transport their bike in a trunk or something, and need to drop the post to make it fit.  But a seat post should also be removed every once in awhile to be lubricated.  You'll need a mark so you don't have to go through this process again.  I use a hack saw to remove a little bit of paint on mine.  You can see that I have three marks on my post now.  The highest was my first setup, the middle was switching to clipless pedals, the lowest is my current setting.

*NOTE*   Do not extend your post past the manufacturer's suggested Minimum Insertion Mark!   A certain amount of the post MUST remain inside the frame.  Otherwise, the portion of your frame where the seat post goes in may simply bend over and break off under rough usage.  I have seen this.  Don't make this mistake.  If the post HAS to come out too far to get the right height, buy a longer seat post!   You can measure the distance out of the frame your current one is, and your current posts length, and determine how long a post you need. 

**Before you buy a longer seat post, skip ahead to the section on Handlebar Height and Tilt.  If you need to buy a longer seat post AND you experience problems with handlebar setup, you should consider getting a different bike.