Drivetrain Blues

Photo from Wikimedia.

I’ve been feeling sore from Saturday’s Climb-a-thon ride: no wonder I got dropped. My calves hurt more than usual so I’ve been taking it “easy” over the last couple of days: I didn’t bike on Sunday to Beacon, as I had wanted to, but I did jump on the track bike on Monday for my daily commute.

It was on this ride that I began to hear my chain slip off the gears, both of them, a problem that has been getting worse throughout the summer. The slipping was so severe that I decided not to ride the bike hard the rest of the day. On Tuesday, I didn’t ride the track bike at all and instead rode my road bike for my daily commute. It was a little much, and I felt like such a dork every time I had to clip out at a stop light. I looked even worse trying to clip back in to my pedals.

Exclusively riding the road bike is not a permanent solution: I have to fix my drivetrain. Hugo from Spokesman Cycles told me that I had to get a whole new drivetrain: a new chainring, a new freewheel, and a new chain. It would set me back about $80 for the parts and about another $40 for the labor.

Although that pricing doesn’t seem terrible, I’d like to try to replace it all myself. I’ve been snooping around and it appears that there’s a lot to this.


I need to figure out the size of the Chainring that I want. I currently have a 46-tooth in the front, and I would like something a little bigger so I can ride a little faster and a bit harder. I’ve settled on a 48-tooth.

Chainrings have a specific size, depending on the diameter of the bolt pattern, known as a bolt circle diameter (or BCD). One very nice guy at a very nice bike shop told me it’s 110 mm, and another guy at a shop down the street, run by some sketchy dudes, told me it’s 130 mm. The spec sheet for my FSA Vero crankset says that my BCD is 130 mm. Credit the sketchy dudes for possibly being correct, although they did try to upsell me on a used (possibly stolen) Sugino 75 crankset for $200.


I also have to replace the freewheel in the rear. I currently have a Shimano 18-tooth freewheel in the rear. I am considering a 17-tooth to significantly increase my gear inches.

Teeth 46 teeth 48 teeth
18 teeth 67.2 gear inches 70.1 gear inches
17 teeth 71.1 gear inches 74.2 gear inches

To install the freewheel, I can either have a bike shop do it, or I can buy the parts necessary to do it. A single-speed freewheel remover has to match the pattern of the freewheel. It turns out that I need to get one, such as the Park Tool FR-6, that is designed for BMX bikes and those with a specific Shimano pattern. I also need something to torque the removal tool, as the tool is basically just a screwdriver bit. I can use a regular crescent wrench, but a lot of gear heads recommend the Park Chain Whip tool since it has a chain on it to better secure the freewheel to the hub. It also has an hex opening that perfectly fits the FR-6.

While the chain whip is nice to have to secure the freewheel, installing the freewheel apparently only requires a little bike lubricant. Pedaling the bike will tighten the freewheel onto the hub, particularly on uphill climbs.


I need to replace the by-now worn chain. My bike requires a single-speed chain, which is sometimes marketed as a 8-speed chain, that’s either 18" or 332" wide by ½" long. I also probably have to remove some links. Hugo recommended I get the KMC Z510.

The collection of drivetrain parts are such that I should decide between 332" and 18". I’ve settled on the larger 18 since they’re thicker and presumably tougher, but going smaller might reduce some weight. It also appears easier to get 332" parts.

And such is the joy of bicycle repair and maintenance.

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