In this installment of our ongoing series on upgrading components, I provide tips and trips related to the job of installing a new bottom bracket and crankset. I started this 2-part BB and Crank piece last week. I like to think of the crankset and the bottom bracket, as the heart of the bicycle. Your frame and wheels are important, but without a crankset and bottom bracket you wouldn’t be able to pedal your bicycle down the road. And, there’s a connection with how fast and hard your heart is working to power and turn the crankset.
When beginning a crankset upgrade, a common mistake is removing the old crankarms with the pedals in place. It’s usually easier to remove them when the crankset’s still in place. It’s also less likely to scratch or bang your crankarms, which matters more on your new setup. A safety tip for removing right pedals is to shift onto the large chainring first. That way, if you should slip with your wrench and slam your hand or arm into the chainring, you’ll hit the chain, not the teeth. Lastly, look carefully for thin metal pedal washers. Some crank makers provide them and, if so, save them for use on your new crank if they’re required.
Check chainring bolts on new cranksets
It’s not as common as it used to be to find loose chainring bolts on new cranksets. But I still recommend checking for them. All it takes is using the appropriate tool and turning each bolt clockwise to make sure it’s tight. The most common tool is a 5mm allen wrench. But some makers now use torx bolts, meaning you’ll need a size T25 torx tool.
If I find a loose chainring bolt, I remove it and feel and inspect it to see if it’s been lubricated at the factory. If not, I remove that bolt and its other half, which is still in the other chainring. I then lubricate it with a little grease on the threads and surfaces and put it back in and tighten. And, since that one bolt wasn’t lubed enough, the rest aren’t, either. So, I remove and lube them, too. This ensures they stay tight and also that they don’t click or creak over time.
Protect your new crankset
I like to put protective tape on crankarms to prevent heel/foot rub wearing off the beautiful finish and any logos. What I use is a product called Crankskins. For about $10, you get a kit with 8mil-thick clear die-cut vinyl protective panels with a high bond adhesive.
Follow manufacturer’s removal and installation instructions
With new crankset and bottom bracket designs coming out every new model year, it’s important to find, read and understand the instructions for removing your old and installing your new parts. Check the company website for documentation. If you’re lucky they might provide a step-by-step video you can watch while performing your upgrade.
Of special value are any dedicated tools they explain or show that are required for their specific bottom bracket or crankset. As quickly as designs change, new tools come along, too. And having the right tool(s) can make an install easier and ensure the best performance.
Don’t overtighten the bottom bracket bearings
When you’re all done installing the new bottom bracket and crankset – and before you put the chain on the chainring, try turning the crankarms by hand to feel how easily the crankset turns. It should feel silky smooth with a slight hydraulic resistance (from the grease inside the sealed bearings). You’ll feel a little resistance, but not much.
If the crankset is binding and hard to turn, it’s a sure sign that something about the install is wrong. An example is making the mistake of tightening the dickens out of a Shimano end cap thinking that that’s what’s holding the crankarm on. If you do that, you can overtighten the bottom bracket bearings so severely that you’ll barely be able to pedal the bike.
If you find that the crankset is binding like this, try taking it apart and putting it together again. But this time, focus on every piece of the assembly during installation to make sure it’s all fitting together perfectly. Keep in mind, too, that most modern bottom brackets use sealed cartridge bearings that don’t feature micro-adjustment. In other words, there’s no fine-tuning the adjustment. It’s either right or wrong.
Use a torque wrench
The instructions with modern components include the torque specifications. You’ll need a torque wrench and the right size bits for your parts in order to tighten correctly.
After your first rides, check your work
After a couple of rides, be sure to check your crankarms and bottom bracket to ensure everything is tight and still adjusted. If anything’s going to loosen, it will usually happen soon after installation. Of particular concern is the left side (non drive-side) crankarms held by bolts. You want to catch any loosening before something lets you down on a ride.
Install pedals carefully
Many a crankset installation has been botched by rushing to get the pedals on and mistakenly forcing a left pedal into the right crankarm or vice versa (this can ruin the threads in the crankarm). So take your time and look for the R and L mark on the pedals so you get them on the correct side.
Also, start them by hand, never force them. And don’t forget the pedal washers if they are required. If the pedals are not still lubed from before, apply a little grease to the threads. Remember that the right (drive-side) pedal is turned clockwise to tighten. The left pedal is turned counterclockwise. Pedal wrenches are usually large enough to tighten pedals more than enough, so don’t go crazy or you won’t be able to remove them without a fight should you need to box your bike or upgrade pedals.
Remember to add your great crankset and bottom bracket tips and tricks via the Comments section below in the Newsletter version of this article.
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s streak of consecutive cycling days has reached more than 8,000. Click to read Jim’s full bio.