Noisy drive train

[jane]

I have an old (1973ish) much loved (my first proper bike) Holdsworth Equipe which I recently stripped down to a singlespeed. At first I just removed the rear derailleur and shift levers, leaving the double crankset on the front and putting an old but unused 26" 1 1/4 wheel with singlespeed freewheel on the rear using just the small 40t chainring on the front. It worked just fine like this- smooth, great chainline- silent.  However, my daughter, who likes to ride this bike when she's in London (apparently, after nearly 40 years it has become "sick" and "cool") had one moan about it- the double chainring on the crankset diiminished its sickness and coolness apparently.  As the chainrings were  a bit worn I agreed I would replace them and dug out an old stronglight 42t plus a couple of cranks from the shed.  Put them on (with new bottom bracket and new pedals) plus my daughter fitted a new wheel with flip flop hub (she likes to play at fixed sometimes-) A few weeks later the whole set up has developed the most alarming creaking with every pedal turn on both sides.  And I cannot work out why- the whole setup seems solid and firm.  Chain as  tight as a, well, a tight thing. What can I do? 
      Mystified, London

[iakobski]

First guess would be chainring bolts. Slightly loose and they will give a most alarming amount of noise.

Check tightness of crank bolts too, but not likely to make as much noise as the chainring bolts.

[jane]

Everything's tight- first thing I did was to refit everything, making sure everything was OK.  I had  to use a small sized bottom bracket- is it possible it could be too small for the crank arm even though everything appeared to fit?  I have to admit it's a long time since I did this job on this bike and the last time I knew exactly what I needed and had no trouble getting it- it was a little bit more mix and match this time.

[border-rider]

You haven't mixed ISO and Japanese tapers have you ?

[jane]

I'm not sure! I note that the mighty Sheldon in all his wisdom says this can be done. It is possible, as in chatting to the LBS who sourced the BB for me they said something about using one which would get the crankarm sat in the right position to get the best possible chainline.  I used the bottom bracket the LBS got for me and I just put it in without asking or looking very carefully at it.  The cranks are Stronglight so I would guess are ISO.  The crank would probably sit a bit further out wouldn't it?If this is indeed the case, would it cause the alarming creaking/grinding noise which has developed? 

[border-rider]

Newer Stronglight is Japanese taper, I think.

Yes you can often get away with it, though very occasionally it may be a problem.  It might explain the noise...

[Ian H]

If it's an old chainset it might be that it and the axle are not mating perfectly, either because of dirt or wear. There might be a step worn inside the taper hole from a previous fitting. Try tweaking the crank bolts just a bit tighter.

One old chainset I had spread enough that the axle came right through and the bolt bottomed out.

[teethgrinder]

You say the chain is nice and tight. Is it too tight?
Sronglight chainrings aren't the best that money can buy and yours may have tight spots. Or it could be the sprocket. Maybe even an exentric chainring or sprocket.
I've had a squeaking drive train because my chain was too tight. I rode 60 miles on it without noticing until I swiched off my MP3 player

You see, your chain. It needs to be a liiiiitle bit slack.

[TimO]

You see, your chain. It needs to be a liiiiitle bit slack.

Burn the heretic!