Tuesday, September 14, 2010

Cassettes and remasters

It has been a while since I have had a chance to do any work on the project bike and I have begun to get itchy to get on with it. Sadly, my youngest is now at school full time and the list of jobs that need doing round the house have got measurably longer. I often joke to the wife that since we have reversed roles it is her who is supposed to approach the DIY etc, but sadly she insists on baking cakes so what can a man do? It is true that the way to a man's heart is through his stomach.  This then is the reason that I am back on the bikes.

So today have completed my allotted set of chores and kept house, I find I have half an hour spare. Time in which to change the cassette on the rear wheel. This consists of unlocking a nut on the rear wheel and swapping over all the parts without dropping any of them. The theory is that providing the cassette (that's the selection of gears at the back of the bike) and the freewheel (which connects them to the rear hub) are compatible it is a simple replacement job.

I start first with the removing the tyre on the wheel, not because it is necessary, but because I wish to check how true or straight the wheel runs on the axle. The wheels have been sold as no visible wobble, but it is probably best to check now and tweak the wheel into shape rather than find out when it is on the bike. While I am doing this I read the wheel size on the tyre 26x2.4 hmmm that could be problematic finding replacements. Note to self when buying secondhand rims check the tyre dimensions.  It also starts to try and rain, I pray it will hold off long enough for me to finish the job outside.

The lockring on the original 8 cogs is a little stiff but the with a little shimmy it opens easily enough and allows me to slide the original cassette of the freewheel. I put this in a bag for later. Maybe I can use them or sell them, either way they will need a clean. Which is what I set about doing to the freewheel. It is not particularly dirty, unlike the rime which is shedding black stuff all over me and the light coloured T-shirt I am wearing. However, I think that if I am building from the ground up it is best if the whole thing is as clean and dirt free as possible. Some degreaser and a good scrub and all is clean. Now to add the new cassette.

The cassette is a SRAM PG970 9 speed, and it glows with a satin finish at me from within its packet. A packet that turns out to be all but impenetrable. Not wanting to score the metalwork with a knifeblade I battle the finally wrap until it begins to give up its precious cargo. At last, eyes shining, I remove the cassette unbroken, until near the end I find a wad of plastic bag inserted in the middle. Removing this proves to be the straw that breaks the camel's back and the last two cogs come loose with the lockring. Oh well not a disaster.  I take the bulk of the cassette and start to fit it to the freewheel. It takes a couple of minutes to realise and locate the alignment spline which is smaller than the others. More a process of elimination here as I go round the set trying each one until it slides smoothly in. Now for the last two cogs, and here is where it really gets messy, because now they are separated from the rest, I really don't know which side is wheel side and which isn't. It takes a few moments of staring at how it will work for me to finally put it all together. Lockring on and tightened with the splined tool and the hole process is finished.

So there is another blind myth explored - if you create a sensible design with a finite series of combinations then the pathways are forced to accept one design over another. Oh and it starts raining after I have put the tools away. Time for the school run.

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