Replacing the Bottom Bracket on my Budget Bike from Amazon

This is my Vilano hybrid bike. I ordered it off Amazon 7 years ago and outfitted it with some fenders and a cargo rack. The total cost for the bike and accessories was just under $300, so you know this is a cheap bike. For the price, it has been fairly reliable. Aside from quick trips to/from the gym and back, I have taken it on distances as far as 15 – 20 miles. Regarding repairs, I've had to replace a few broken spokes in the past, which wasn't too difficult; I had to learn how to do those repairs myself. The reasons here being:

1) the bike is cheap, repair costs from a shop would exceed the cost of a replacement bike of this style

2) when I brought the wheel to a bike shop for advice, they essentially told me to toss the bike and get a better one.

Now 7 years later the bike has developed a new problem. When I'd pedal, there would be a subtle 'thunk' in the crank area every revolution. Researching the problem online said the bottom bracket bearings were failing.

This would be the first time I'd remove a crank to replace a bottom bracket. (Ironically, this is also the second post about replacing a bottom bracket on this blog) Where do I being?

The Amazon listing for the bike had vanished off the internet, so I wouldn't be able to scan the reviews/questions for help there.

The brand itself barely has an online presence today. Fortunately there was a listing for a “modernized” version of the bike I bought; it looked identical, but with disc brakes and different gearing. One of the users answering comments on the listing had some helpful information.

To replace the bottom bracket on my Vilano Hybrid Bike, I'd need a toolset to remove the 3 piece crankset/bottom bracket from a square tapered setup with a 20 tooth spline (something like this). The bottom bracket for this frame is a Shimano BB-UN300 equivalent. Looking over the bike and the readings, this made sense given the gearset on this bike is Shimano. Thank goodness for a standardized system!

The user listed the dimensions of the bottom bracket to be 68mm x 119 mm. My search showed 119 mm was not a standard size, so I bought 2 different sized bottom brackets, a 68 x 117.5 mm, and a 68 x 120 mm. I'd be ready for whatever size bracket emerges from that frame (spoilers: it was the 120mm)

Thanks to the numerous videos online of how to do this, it wasn't too hard to jump into this task, but there were some steps where I scratched my head for a bit.

To start, the dust cover/outer crank-bolts needed to be removed. These are held in by a 8 mm Allen key. Somehow I didn't have an 8 mm Allen key in my toolset, but that's where the toolset came in. Ideally I'd have a 8 mm Allen drive bit to use with my ratchet set in the future, but this wrench worked fine for removing the bolts.

With the 2 outer bolts off, the next step is to use the crank removal tool to yank wedge the crank arms off. The shorter and wider black “plug” threads into each crank arm. Then the “mandrel” threads into the plug to push the crank arm off the bottom bracket. I found the supplied spanner with the tool set a bit weak, so I grabbed a 5/8” open headed wrench to do my torqueing. It took me a few tries to realize I wasn't cranking hard enough with the mandrel to force the crank off (I was afraid of breaking something), but after a few attempts and some TriFlow later, I managed to remove both arms. To note with this tool, installation and removal is the standard right-hand threading.

For the bottom bracket, the holders are embedded with a 20 tooth spline. The toolset came with a special fitting for this. For torqueing this fitting, the toolset also had an adapter for the allen key to make it act as a half inch drive. I'd rather use a ratchet for this, but the provided tool worked. On the drive side (right if you're facing forward), the threads for the bottom bracket are reverse threaded, so you turn the drive to the right to loosen it. These holders came out easier than the crankarms.

Now with the bottom bracket removed, I could see the correct measurement for this bike. And fortunately it was the same length as one of the ones I purchased. The bottom brackets are inexpensive, so if this new one breaks, it won't be the end of the world.

Also to note because of the threading, the bottom bracket is uni-directional, so it only fits in one way.

The new bottom bracket goes in just as the old one came out. Before installing, I hit the threads with some Red and Tacky Grease for the anti-seize properties. I installed the bracket holder on the left side first, then inserted the unit to the drive side (remember, left hand threads!) and tightened that down. I don't have torque specs for this, so I just went hand tight on both sides.

For reinstalling the crank arms, this I needed to check what I needed to do to reinstall the arms, if I needed another tool. It turns out you use the 8 mm Allen head bolts to secure/force the arms back onto the taper. I put the left side crank arm first and tightened that bolt down as far as I could by hand (again, no torque wrench or specs here). Drive side next after reattaching the chain and aligning the arm to 180 degrees of the other side (not too hard to mess up the alignment given it's a square taper).

And that was it. I test rode the bike and there was no more clunking. This wasn't too bad to do. I hope this article helps someone else who bought this bike and needs to make some repairs or upgrades.

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