Sunday, August 12, 2012

The Novice Bike Mechanic ( Part 2 )

Part 1 described how I went about removing the chain rings on my 1961 Mercian Audax with the aim of replacing them with a more hilly friendly version as I prepare for a life of cycling in my dotage. One of the main obstacles I encountered was the question of how much force to use to loosen the threads, many of which had seized up over the decades since the bike was last stripped and assembled.
Re-building with new components is in theory a simple process of just reversing the process but life for me never seems that simple and for a bodge-it man could present many challenges. What I needed was a book!   And my GS Gazzetta friends came up with an excellent suggestion

So armed with my new fount of knowledge I started the rebuilding process. Stage 1 was to insert the new Bottom Bracket, having first cleaned out all the accumulated dirt and debris which had collected in the shell. The insertion bit was quite easy and the tightening of the shell thread, enough to pinch tight but not to endanger the thread stipping. Feeling quite good so far.

Just a slight smear of grease on the new crank threads and we were nearly there. I was very wary of over tightening the crank bolt and in the event, after the bike had been ridden for a few kilometres, I had to return to this and tighten a little more. Perhaps the bolt was still bedding down. The smaller chainset meant that I also had to lower the front derailleur changer, all in accordance with my instructions from ZIM

The old big ring was a 52 tooth size whereas now it had shrunk to 46 and so there was a question about chain length but I am convinced that messing about with link removal is something of a black art..literally when you see how I appear to get grease and oil on my wife’s white towels! So I left it alone and just checked that the gear changer still worked,
And the bike was ready to roll!

However, in practice I discovered that the gear changes were not working as smoothly as I would have liked and I think that the position of the rear derailleur with the longer chain was ( partly? ) to blame. And so it was back to ZIM to find out what to do and what was needed. The recommendation of a Park Chain Tool to squeeze the links together when removing a SRAM link was excellent and made the job so much easier. Calculating the new chain length according to ZIM ( my new bike mechanic phrase ) I used another Park Tool to remove a few links and then reassembled everything and tried again

This time everything seems to be working.

Whilst I would not now call myself even a reasonable bike mechanic, I have enjoyed this exercise, made more enjoyable by not being under time pressure as I had another bike to ride. It has also given me a deeper understanding of how the whole thing works..problem is I am now listening out to every creak, groan that my Mercian makes and spend a ride trying to diagnose non-existent problems. Oh, and I do now have the basis for a set of good quality bike tools.

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