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Chain Sizing & Installation

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properly sized chain

wrap around outer ringFor this procedure we will need to have the bicycle on a level surface.  You can keep the bike in your stand just make sure that the wheels are level with the ground.  You will also need to make sure you have a chain tool handy.  (Even if you are using a SRAM Power-Link you will need a chain tool to cut the chain to size.)  First we need to shift the bicycle to the outermost cassette cog (smallest freewheel cog) and the outermost (large) chainring.  Once the derailleurs are in this position you can begin by feeding the full length chain through the rear derailleur and around the cassette (rear cogs).  Pull enough chain through that you can wrap the chain all the way around the big chainring.  You should now have chain hanging from the front chainring and rear derailleur.

Take the chain ends and begin to pull them together.  For this part of the process we are going to focus our attention to the rear derailleur and use it as a gauge to let us know how long our chain needs to be.  As you pull the chain together, and begin overlapping the chain ends, watch the rear derailleur for the point at which the pulley wheels are perpendicular to the ground.  This is the point at which the chain is properly sized.  The overlapping piece of chain will need to be removed with a chain tool.  If you are using a SRAM Power-Link you will want to be sure that you have two inner chain plates at the ends when you cut the chain.  If you are not using a master link you will need an inner plate on one end and outer plate on the other end.

pull chain together
Most chains will come with two inner plates showing on the ends.  In this case you will need to partially remove a chain rivet making sure that this will leave an outer plate showing.  The picture to the right displays the proper rivet protrusion that should be showing in the outer plate.  It is very important that we do not totally remove the rivet as we will use it to hold the chain in place and eventually push it back through to reinstall the chain.  It is also nearly impossible to put a rivet back into the chain plate after it has been totally removed.  If you push the rivet out by accident go to the next available outer plate on the chain and try again.  You will then want to cut one link from the excess chain you removed earlier to replace the link we lost by pushing the rivet out.

reinstalling the chainouter plate pin paritally removed

We are now going to reconnect the chain.  To make the process easier you can carefully take the chain off the outside of the outer chainring in the front to give yourself some extra slack.  Reconnecting the pieces can sometimes be trickey.  You will want to start the inner plates at an angle.  This will help guide the inner plate over the rivet protruding from the outer plate.  Once you get it started a little pressure will snap the chain into place.  You can now lay the chain into your chain tool and push the pin back through the inner plate and into the opposite outer plate.  Go slow and make sure the pin is even on both sides of the outer plate. 

Shimano chain pinShimano Chain Users READ, Others SKIP:
If you are using a Shimano chain you can not push the same pin back through the inner and outer plates.  Shimano rivets (pins) are beveled on each side for added strength.  This is good in functionality until your chain breaks or you are sizing a new chain.  Once the pin is pushed through it flattens out the bevel and weakens that link.  For this reason your new Shimano chain will come with two chain pins.  These pins include a guide portion and a replacement rivet.  The image to the right shows a Shimano chain pin with the section having a rounded nose being the guide section.  To use a Shimano pin insert the guide portion of the pin into the connected piece of the chain.  You will now set this into the chain tool and press the replacement rivet into place.  You can then snap off the guide portion of the pin with a pair of pliers.  Shimano chain pins come in 8, 9, and 10-speed widths so be sure to purchase the correct on for your chain.

You chain is now sized and installed, but the work is not over. During the process of reinstalling the chain pin with you chain tool you are squeezing the plates together. This often leaves you with a tight link.  Bend the installed link and watch to see if it straightens itself out.  If not you have a tight link.  To remove, take hold of each side of the link (one in each hand) and flex the chain side to side to loosen up the link.  Test the link again by bending and watching to see if it straightens out.

a tight link will remain bentflex the chain with both hands at the rivet

If it seems OK the final test is to back pedal the bicycle cranks with the chain on the smallest rear cog and watch to see if the chain or rear derailleur jumps as the chain goes through.  If so the link still needs a bit of work.  Repeat the flexing of the link until if pivots smooth.

You are now ready to roll. This sizing procedure works for 90% of bicycles. You should still check that the chain is long enough to go from the big cog in the front to the big cog in the back. With the popularity of Power-Links the installation process has become easier but you will still need to remove some links to correctly size your chain. If you have any question drop me a line or bring your bike to your IBD (local independent bicycle dealer) and they can get you setup.

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