Mercian King Of Mercia Build - Decisions,Decisions!
- Thread starter winjohn
- Start date
bikeworkshop
Senior Retro Guru
The distance between axle and derailleur mount, and its relative angle, can make 32 or 34 the limit, but chain length and derailleur tension seem to pay a part too - oh and the b-adjust
I set the thing up by putting the chain on the smallest cog and the smallest chain wheel. I split the chain so that the mech was just still providing tension. This meant the chain could not have been left any longer than this in this set up. Then when going up to the big chain wheel the chain was too short to allow the mech to select the largest cog.
I guess I could try a hanger extender (I have one) and I have heard the B screw adjust can help.
I can see how adjusting the b screw could allow a little longer chain to be left but I can't see it gaining much. I might try the extender too since I have one.
I can now see I made a mistake in my sequencing of this. If I had started on "big/big" then moved to "small/small" i would have not cut the chain so short which would have left me the options of trying the B screw and wolf tooth fixes. Every day's a school day when fixing old bikes!
The low-normal XT seems to shift a little better though, crisper and quieter. I guess it is a newer design. I now have both options as possibles but I feel that I will always be close to the limit with the older standard cage XT and the newer one is under less strain.
I'll see how things work out over a few rides. Things to consider are:
1. Which one works best during riding, ease of use, noise, reliability.
2. Which one looks better.
3 Whether I am at all bothered about period authenticity with this build or whether fitness for pupose is more important. I think I am leaning towards the later.
Since these Mercians are pretty much custom builds there is no original right specification although obviously for some, the period authenticity is important. The KoM was built for a tough high mileage job though and I'd imagine most owners over the years would change parts as they wore out with newer kit as it became available so I feel I am paying homage to that philosophy here.
I guess I could try a hanger extender (I have one) and I have heard the B screw adjust can help.
I can see how adjusting the b screw could allow a little longer chain to be left but I can't see it gaining much. I might try the extender too since I have one.
I can now see I made a mistake in my sequencing of this. If I had started on "big/big" then moved to "small/small" i would have not cut the chain so short which would have left me the options of trying the B screw and wolf tooth fixes. Every day's a school day when fixing old bikes!
The low-normal XT seems to shift a little better though, crisper and quieter. I guess it is a newer design. I now have both options as possibles but I feel that I will always be close to the limit with the older standard cage XT and the newer one is under less strain.
I'll see how things work out over a few rides. Things to consider are:
1. Which one works best during riding, ease of use, noise, reliability.
2. Which one looks better.
3 Whether I am at all bothered about period authenticity with this build or whether fitness for pupose is more important. I think I am leaning towards the later.
Since these Mercians are pretty much custom builds there is no original right specification although obviously for some, the period authenticity is important. The KoM was built for a tough high mileage job though and I'd imagine most owners over the years would change parts as they wore out with newer kit as it became available so I feel I am paying homage to that philosophy here.
Guinessisgoodforyou
rBotM Winner
Set your chain length big on big plus two links.
If you like the triple but aren't going to need the big gears, get a chain guard.
Then you can put a neater double FC on and never have scraped knuckles from the chainset when fettling.
Easier to clean as well. And no need for trouser toe clips on the Mercian
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I was think of a chain guard and getting rid of the big ring but instead lost the granny since I had the chainrings available to give me 46/34 which seems a good range.
I am now looking at the chainline to see which option gives the best result.
Having the chain guard is definitely a good idea though.
Nice bike btw
I am now looking at the chainline to see which option gives the best result.
Having the chain guard is definitely a good idea though.
Nice bike btw
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