Chainwheel rubbing chainstay problem

I am putting together my first build. I have a wheel with a Miche hub. The frame came with a bottom bracket for a cottered chainwheel and I thought, for the sake of convenience and expense, I would stick with that BB and buy a new 46t chainwheel.

I have only handtightened the chainwheel but it looks like it will rub against the chainstays (see red ring in photo below). This may have been a problem for the previous owner as the paintwork is marked at this point.

It seems to me that I am probably going to need to get a new BB (the chainline is not so great with the present set up either) so my two questions are:

• does anyone have an alternative suggestion for solving this?
  
• does anyone have any good advice for finding a suitable BB?
  

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I wouldve thought youd get a spindle with the new cranks.

Well you clearly need a new bottom bracket. that chainline is unworkable. And while your at it you may aswell update your chainset technology by about 50years and get a regular square taper setup.

Any bottom bracket will do as long as the spindle is a good few mm longer than you existing one, the shimano UN ones are fine, cheap & hassle free. Just make sure your BB doesnt have strange threadings.

Probably best to actually work out what the chainline measurement is at the rear first.

Measure the rear hub if you don't know its width (120 / 130 / 135 etc). Measure the distance between the inside of the dropout (drive side) to the middle of the teeth on the sprocket. To get the rear chainline measurement you just do:

(hub/2) - dropout_to_sprocket.

You now need to work out what size BB to put it based on the previous measurement. First, measure from the centre of the seattube to the middle of the teeth on the chainring. The difference between this distance and the rear chainline measurement is how far out your chainline is.

Suppose that the rear measurement was say 48mm, and the front was 31mm then you know you need to find 9mm -- which would equate to getting a BB that was 18mm longer than your current one.

Hope that helps somewhat.

I am putting together my first build. I have a wheel with a Miche hub. The frame came with a bottom bracket for a cottered chainwheel and I thought, for the sake of convenience and expense, I would stick with that BB and buy a new 46t chainwheel.

I have only handtightened the chainwheel but it looks like it will rub against the chainstays (see red ring in photo below). This may have been a problem for the previous owner as the paintwork is marked at this point.

It seems to me that I am probably going to need to get a new BB (the chainline is not so great with the present set up either) so my two questions are:

• does anyone have an alternative suggestion for solving this?
  
• does anyone have any good advice for finding a suitable BB?
  

Thanks both for the advice. I'll go and get my tape measure out.

give it a love tap with a wooden mallet

Sturmey Archer spacer available from most bike shops fitted between right hand cup and frame will bring it out 2mm.....should do the trick!

You could still end up with a naff chainline though. The best solution would be to find the right sized bottom bracket (if one exists). If you can't find the right sized bracket then yes, space the fucker out.

Sturmey Archer spacer available from most bike shops fitted between right hand cup and frame will bring it out 2mm.....should do the trick!

hammer and block of wood.

Took me a while to find that tape measure. Having looked again it turned out the rear wheel was not on straight and so the chainline is not so bad (1mm out - front line wider).

A spacer sounds like a good option but would I have to file down the cotter pin to get the chainring on?

Hammer and block of wood sounds intriguing. Are you suggesting I just bash the edges of the chainring out so it becomes concave?

Thanks for the help.

I had this problem, Miche bb has worked for me so far.

Hammer and block of wood sounds intriguing. Are you suggesting I just bash the edges of the chainring out so it becomes concave?

No, you dent / flatten the chainstay at the contact point until the chainwheel clears it.

No, you dent / flatten the chainstay at the contact point until the chainwheel clears it.

Thanks. I may well give that a bash.

Use a 42T