Removing / Changing a Mountain or Road Bike Crankset
Ok, so your chainrings are worn out/ broken, or maybe you snapped a crank arm, or perhaps you just want to put on a new lighter stiffer crankset. Well to do that you need to remove the old one right? I'll walk you through this process which is incredibly simple but frustrating if you don't have the right tools.
Tools you need:
Crank Puller - YES YOU NEED THIS. I can't tell you how many people came into the shop after screwing up cranks by trying to remove them without a puller. Ok, a hammer is not a good way to remove a crankset. It is however, a good way to damage one, and damage your bottom block. Some tried to make their own puller. Listen, don't do that. The threads on the crankset are different than most bolts you are going to find, to avoid stripping the threads or getting a bolt stuck please spend the fifteen bucks and get a crank puller.
8mm allem / hex wrench
Optional: Hex set for chainring removal
Yup that's it. I recommend the compact crank remover from park tool. It is small, works for just about any crankset and is proably your cheapest option. It is built to take a lot of abuse and I have had mine for five years and never had a single issue.
It is optional to remove the bolts that hold the chain rings on to the crankset. The large ring will come right off over the pedals. The two inner rings will just hang there.
I usually remove the chainrings on older bikes because they can be stuck on very tightly and you get a bit more leverage when they are still on the bike.
Start by removing the rank fixing bolts, with an 8mm hex or allen key. Make sure you remove the dust caps on an octalink or isis style crankset. The fixing bolt for these will inside the threads, instead of directly on the outside like a square taper crank.
A crank puller is essentially two parts. It is a large hollow outer piece which is dual threaded. A bolt with a specific sized washer or endcap is moved through the inner threads. Essentially, the large piece anchors the puller to the crank and the inner piece pushes against the bottom block to force off the crank.
To start, insert the large hollow portion of the crank puller into the crank. Make sure that the inner portion is removed or nearly so. Using a crescent wrench make sure the puller is fully inserted. This is important, make sure the puller is fully inserted or you can strip off the threads on the crank and give yourself a completely new problem.
Now thread the inner portion of the crank puller until it stops. If using the compact crank pouller, make sure you use the right side or the correct washer. The smaller side / washer will be for square taper cranks while the larger side will be fore octalink or isis style cranks.
Brace the pedals with something, don't try to hold them with your hand. If the bike is on its side I find that using my foot as a brace is usually adequate. Using the cresent wrench tighten the inner portion. It will be very difficult at first as the cranks break free. After a few turns the effort should be minimal, at which point you can remove the crank with your hands.
Check the bottom block for damage, replace your chainrings, or put the new crank on (make sure the pedals are in the right spot) and use the crank fixing bolt, and the 8mm hex to secure the crankset.
Thats all there is to it, and by doing this job yourself you easily save you more than the cost of the crank puller. Good luck!