Bottom Brackets

I ride an old Halfords Apollo Mogul bicycle to commute to work. The bike is about 10 years old, and it had hardly been used for the first 8 years of it’s life, but a change of work location made cycling an ideal form of transport for me.

I had a spate of punctures a couple of months ago, it felt like I was replacing or repairing the inner tubes about once a week. The original tyres were getting baldy in places, so I bought some cheap Rolson tyres from Argos, and the punctures stopped immediately. I should have replaced them much sooner! The only other repair I had ever done was to replace the rear brake pads. I’ve not had much luck with those as I have never been able to get the v-brake pads to meet the rim at the same time. I have tinkered with the brake cable and tension screws and the results are that I either ride with one pad touching the wheel rim and slowing it down, or worse still, the brakes not slowing the bike at all. Luckily, the front brake on this bike is a Zoom disc brake which does a decent job of slowing the bike down by itself.

At the weekend I attempted to fix the wobbly pedal issue that had gotten worse. The wobble is actually pedal ‘axle’ which I now know to be called the bottom bracket. I watched a couple of YouTube videos to see how to replace this. I was very surprised to find there are a large number of different standards and sizes of bottom bracket. I was not able to find which one I had, so I decided to remove mine and find a replacement that will fit.

I had recently purchased an Icetoolz bicycle maintenance kit from eBay. I used their Click and Collect service and had it delivered to my local Argos, which is very useful as it isn’t always possible to stay home and wait for a delivery. I used the crank removal tool to remove the crank (the pedal arm), which was straight forward. I then had the bottom bracket to remove, but I needed a tool I didn’t have, and I didn’t even know what the tool is called. A google search eventually found I needed an Adjustable Cup wrench (spanner) and I purchased a suitable tool, an Unior 1672/2, from Amazon. I took advantage of the Amazon Prime trial to get free next day delivery (on a Sunday!) and added additional items including brake pads, bike grease, a new bottom bracket, and a bike stand to help with the repairs.

The bottom bracket I bought is a Shimano UN55. They come in various sizes, I had to measure the width of the part of the bike frame it sits in, and also the width of the spindles which the crank arms attach to. The available dimensions of the bottom brackets vary by only a couple of millimeters, and I found it hard to take precise measurements when the bracket was on the bike, but I settled on measurements of 68mm and 120mm. The available sizes are 68mm or 73mm, and various other measurements for the spindles with the closest being 118mm or 122.5mm. I opted for 122.5mm as I thought it would be better to be slightly too wide, than too short.

When the packages arrived, I set about using my new Adjustable Cup spanner to remove the existing Bottom Bracket (BB). This proved to be extremely tough and took an additional pair of hands to hit the end of the tool with a hammer as I held it in place. It eventually loosened enough to unscrew from the frame, and once it was off, I found it was extremely rusty with broken ball bearing cages and loose ball bearings. I cleaned the frame as much as I could using a cloth and some WD40, then inserted the new Shimano BB. This was also tough to screw in due to the rust, but with some bike grease, and the correct BB tool (for Hollowtech II BB) from my Icetoolz kit, I secured the BB into the frame. I had issues with putting the cranks back on, they didn’t seem to fit as far into the square tapered spindles as they did on the old BB. They seem tight enough, but there is a noticeable gap between the cranks and the frame which is much bigger than the 2.5mm I was expecting. I used the bike to commute with today, and pedaling was a much smoother experience. The additional gap didn’t affect my pedaling, but I will need to adjust the derailleur to access all of the gears. I will do this next weekend, along with fixing the brakes. All these jobs will be much easier now I have the impressive bike stand, the Ultrasport Bike Stand Expert. I will write another blog next week with an update on my progress.

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