A Grim North

Musings from a northerner living in the deep south…

Cranking it up

Posted by Alan on May 11, 2012

Snapped Crank


A few weeks ago I was unlucky enough to suffer a snapped crank whilst cycling to work. As you can see from the dirt in the stub above, this must have been a fairly old injury that had been gradually worsening over time. Even though I am not very mechanically minded, I set out to find the tools and parts to repair. (If you aren’t interested in bikes stop reading now.)


Old and new components side by side

The style has certainly changed a little in the 10-15 years my Brompton has existed but importantly not the dimensions or the fittings. The first important tool required was a socket set, a fairly standard piece of kit that I didn’t have. Nut out, the next step is to use the crank puller alongside a bit of You Tube to understand how it worked. A little bit of WD 40 strategically squirted inside the crank stub and it came off pretty easily with minimal swearing!

Naked Bottom Bracket

Naked Bottom Bracket

Cleaning up the bottom bracket it was easy to then slide on the new crank which was then duly bolted on. The last stage was to add the new folding pedal – I chose the brand new Brompton metal 2012 one in the hope that it might last a bit.


Repair complete

My next challenge is to find a way of preventing the bike destroying the small saddle bag I have – notice the axle just to the left of the pedal, as I cycle along the rough edge has started to work its way through the canvas of the back. I know I need some kind of cap nut to round off the end and prevent this, but not which – I suspect 10mm as that is the thread size of the axle. Answers in the comments please if you know!


Heron on the Lea Navigation

Following the repair I took it out for a 10mi (16km) test ride – all seems OK bar a new click in the bottom bracket. It probably needs some strategic oiling and some time to settle, after all this is an old bike.


6 Responses to “Cranking it up”

  1. That’s an awful lot of axle protrusion there, the Brompton version of that hub usually comes with a shorter axle. I can post you a bit of protective vinyl from work if you like.

  2. CHANGING a crank is not hard. BREAKING a crank requires real effort!

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