The second part of the bike to deal with is the drivetrain – the crankset and the bottom bracket (further on BB). Cranksets (and BBs) come in many different varieties. If you look at the first posted image, you can see three different cranksets I had around – Shimano Deore, using the so-called Hollowtech technology, an older Shimano sqaure taper crankset and a newer FSA crankset using the BB30 technology. Not to get too technical – there are many standards out there and you can easily get lost. The first thing you should check is what kind of a BB your frame supports. See if the BB shell (lowest part of the bike) has threads. Next, measure the width of the shell. When you go around looking for a crankset, this info should be enough. In my case, the shell is threaded and has a width of 73mm. To read more about these standards, you can look at wikipedia or, even better, here.
Ingredients and tools:
- crankset (w/wo chainrings)
- extra chainrings (if you’d like) with threads
- anti-seize compound – ASC (very useful)
- bike grease (car lithium grease will also be fine)
- torque wrench (optional)
- specialty tools for BB/crankset assembly (optional)
- some rags or toilet paper for cleaning
Time and cost:
This can take about 15-20 minutes. The cost depends mostly on what you have lying around or have to buy.
1. Get all the parts you need in one place. I find this the best way to start a job. It is unfortunate when you start doing something only to find you are missing a part. In this image you can see all the listed stuff. Besides the parts that I used, there are also some extra cranksets, crank arms and chainrings. This is just so to get a feeling of all the things you can combine.
2. We will start with putting a chainring on the drive-side crank arm. Since I am making my bike to be a city-bike, I plan to use only the large chainring. Place the ring on top of the arm. To fix it, you need crankset bolts, which are a bit special and come with troubles of their own (particularly, specialty nuts). Place some ASC on the bolts and loosely connect the ring on the arm. To tighten, it would be ideal to use a torque wrench and the crank tool (little tool in the center of the picture). The tool is used to provide a counter-torque on the crank nuts (simply put, to stop them from rotating). If you don’t have this tool, then you can hold them with a small screwdriver or some small pliers. Tighten the bolts as good as you can. In the end, wipe clean the whole setup, which is probably messy from the ASC. Also, check if the chainring is sitting tightly on the crankset – there are substantial forces in play when the chain is pulling it.
3. The next step is to install the BB/crankset on your bike. First, clean the whole system and apply some grease on the crankset axle. Now, put the BB in the BB shell on the bike. Usually, the BB’s have the drive-side and the non-drive side designated on them. If not – here is how you find out – on the drive side of the bike (right side when you are on top), the BB thread should be such that it tightens clockwise. On the non-drive side, it tightens counter-clockwise. Place some ASC on the cups, put both cups (separately) in the shell and tighten. Again, if you don’t have the tool, use something else. The tightening torque should be high, so tighten well. After inserting both sides, you can insert the drive-side part of the crankset in the BB. After doing that, wipe everything very well to remove extra grease/ASC. Finally, we need to tighten the crank arm.
4. To tighten the crank arm, you sometimes need some specialty tools (but often not). What I used was a hollowtech II BB, so I needed a special tool. Unfortunately, there is no escaping it. You can see the tool attached to a torque wrench in the image. The torque you should apply depends on the type of crankset (find specs on Internet – here is a handy guide for most you’ll ever need). If you don’t have a torque wrench, tighten well, but not too tight, since this can also be damaging. Finally, there are usually some extra bolts on the crank arm. Mine said to tighten to 12-14 Nm, so that’s what I did. This completes the build-up of your crankset and bottom bracket!