The Dawes, the chain

The ongoing problem of the chain slipping and the gears not working… the Dawes mountain bike really needed to be sorted seeing as I had started to use it a bit more for off road recently (ie, 2 trips on the Downs this year instead of 1 trip last year!!).  I have plans for the whole of the South Downs way at some point, which will need a reliable bike.

Last summer I put knobbly tyres on the bike and took a trip over the Downs.  It was a great ride and showed me huge local bridlepaths and byways over the Downs that make you see the local area in a completly different way.  It also showed me quickly that the chain slipped pretty badly on the Dawes, when you tried to change gear it sometimes did what you thought but mostly it didn’t!   A bit of a problem when going up and down rocky paths and need a new gear pretty instant and realiable.

The Dawes has rapid rise Shamano gearing which means it is all upside down, but shouldn’t be a problem.   A bit of a short lived experiment(?) by Shamano that didn’t last long, good for mountain bikes.  It also has a “mega pulley” deraillier which, according to text I can find, means it will cope with a mega freewheel a lot better – ie a freewheel with a super large low cog out of proportion to all the others (and so a large jump).   I’m not sure if the Dawes is meant to have the mega freewheel to go with the mega pulley, but it doesn’t have it now.  Instead, just an entry level 7 speed Shamano freewheel.

The chain dragged a lot when on all the small cogs, and it slipped all over the place.  Just the time when you are mostly likely trying to get up a steep hill, and you are slipping all over the place – if you manage to get into the gear and not overshoot and the chain jams itself against the spokes.     I did wonder…. if it was expecting a super large low cog then it would explain why it now dragged and slipped without it, the chain was too long.   I pondered about replacing the freewheel with a mega one, but actually I was happy with the ratio of the lowest gear.

A quick fix I though would be reducing the length of the chain by two links.   I removed them quickly and had a look for a new chain pin.  The only one I could find was for a 9 speed chain, so I knew it probably wouldn’t work well but used it anyway.   The pin went in but not unexpected it resulted in the link no longer bending.   Not an immediate problem as it was still enough to let me see how if the slipping had reduced or stopped.  I ventured off for a quick trip up the Downs.

Immediate result in no major slipping and a tighter chain.  In the low gears the chain no longer rubbed along the frame, which had to be good.  With the none bending link it did slip each time it went round, not unexpected but controllable.  I started up the hill and started to go down the gears for real, no massive slipping.  I reached for the lowest gear, under pressure of the hill, and the chain carried on and jammed against the spokes of the wheel.   Not quite a good result, I had forgot to play with the high/low settings that had been a problem before.

On the night ride from London to Brighton years back, I had similar out of the blue (on the Highway bike).  It was pitch black with no light anywhere, and in desperation I fumbled and grabbed the chain with both hands and pulled it as hard as I could to free it.  Amazingly, when I look back, it worked and off I went.   Likewise, years later (again on the Highway) it did it again close to home.  This time it would not unjam and I ended up removing the freewheel, and sweared.

This time I was on top of a hill, but it was a warm sunny evening, so I sat down and started on the task of unjamming the chain.  It did take a little while, but in the end it become free and I continued on for the short circle around the hill and then back home.   A couple more times the chain came off in the same way, but each time super fast reactions meant I braked and stopped before it got really jammed.   Quick adjustments meant I reduced the amount of times it came off, but I did loose the top gears.  It ended up in the gear triggers up and down going up and down, but you never really knew just which gear up or down you would end up in.  Chain slippage seemed fine however, apart from the non bending link.

I left it a week or two until I had some spare time to continue working on the bike.  I thought I would find a proper sized pin or quick link and maybe replace the gear cable.  I couldn’t work out why it was so mad changing gear and could only think the cable wasn’t sliding as well as I should for what ever reason.     My search for the correct sized pin wasn’t good, and neither was the search for the quick link.  Spares at Halfords seems to be something they are starting to limit for some reason, plenty of cheap new bikes but not many spares.   In the end I bought a whole new chain instead.

So today I replaced the gear cable, oiled down all the plastic bits it goes through (3 different bits).  I reset the fine tuning tension thread and I set both the high and low.    I removed the old chain and measured out the new chain.  It is said that you should put a new chain on the two largest cogs, bypassing the derailier.  Measure the length doing that and add two more links on to it.  The result in this case was a chain size the same as I had already made it, and so two links less than what it originaly had.    The chain came with a quick link (I pondered about fitting just that to the existing chain but the freewheel didn’t look worn so thought I would give the new chain a go).    I quickly found that I had missed a bit on threading the chain through the derailier and found that it is quite hard releasing a quick link unless you have the proper tool.   I didn’t have the tool, but I managed to swear a bit and that seemed to do the same job.   I re-threaded the chain, did the quick link back up.  I went up and down the gears while fine tuning the tension screw until I got all 7 gears in all 3 front cogs indexing as they should.

It seemed to work so smoothly while on the stand and up in the air, so I ventured out on the pavement by the house.  Going up and down the driveway, through the gears, the chain didn’t come off.   I repeated, but this time with the front brake slightly on and pressing hard on the pedels to skip down the road, no slipping even in the lowest gear.

A possible success?   Time will tell.  It was getting late and so no time for a trip out up the Downs, maybe during the week or next wekend.   The South Downs ways looks possibly a bit closer.

 

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