Fettling

Not too many pictures today, several posts ago I reported on the chain break as I was cycling up a track on my Marin. I picked up a replacement from "Chris's Bikes" and unfortunately fitted it in a hurry as I needed the bike for a journey. Normally you have to replace both the chain and the cogs at the back (those grubby things with teeth in the photograph). This is because the cogs and chain both wear together. It is quite surprising how much a chain stretches and how much the teeth get worn. In my motorcycling days you constantly had to monitor the chain and as it wore out move the rear wheel backwards to take up the slack. On a bicycle with derailleur gears the dangling thing (the "derailleur part of the rear gear mechanism - which does what it say - derails the chain from one cog to the next) is sprung and maintains tension on the chain as it moves from larger to smaller cogs.

This time around I was hoping to get away with just replacing the chain - to save time really as the chain and cogs (rear block) were not that old. After a bit of cycling around there was quite a lot more noise from the back than I would expect, but put that down to there being too much tension in the chain, it was a link shorter than the chain it replaced. After using the bike for a few short journeys (I have been using my MTB quite a lot recently) I decided that it was: a. making too much noise and b. the gears were a bit skippy on one or two cogs that I would replace the rear block. Normally I take my bikes to the aforementioned "Chris's Bikes" (his placement of the apostrophe by the way) as he does a good job and tests the bikes after fixing them. However I can do my own fettling and over the years have acquired a reasonable collection of the specialist tools to do the work.

For this I needed take off the rear wheel and remove the block and replace it with a new one. It was not necessary to break the chain. For those of you interested in this the Park Cycle Tools website, manufacturers of cycle mechanics tools is a useful source of information on which tools are required. In addition there are a variety of websites offering video tutorials such as this one at Bicycle Tutor (which has commercials) but there seem to be loads on the web. It was a lovely sunny day so I pooped the bike out onto the lawn and had a look. As soon as I turned it over I realised that I had mis-routed the chain. Instead of moving from one small cog to the other on the derailleur bit - it had looped around a small peg roughly where the green arrow points in the picture and so kept rubbing against the peg. This had the effect of increasing the noise, resistance and tension in the chain. So instead of replacing the rear block I re-routed the chain.

So I needed to split the chain re-route it and re-join it. Normally you have to force a rivet through the correspond links of the chain to join it and conversely force one out to split it. This requires a chain splitter. However when I picked up the chain Chris also supplied me with an SRAM Split Link. This is a special link that can be separated without special tools. Essentially you push both ends of the link together and it comes apart. In this picture you can see the link - it is golden in colour and when the rivet is pushed towards the larger hole (pointed to by the red arrow) it will come apart. Unfortunately try as I might it would not separate, I thought I would have to split the chain elsewhere, but a quick check in the web highlighted the error of my ways. To separate the link you need to first squeeze the plates together and then push the links together - with that it came apart easily. Now I have re-routed the chain it runs smoothly and quietly. I will give it a few miles before I decide whether I need to replace the rear cassette.

I must spend a little time giving the bike a clean as well!