Front mech replacement

[paul white]

I have an old peugeot 301 which I have pulled out of the shed to do up, and have discovered the thread has gone on the cable tightening bolt hole in the front mech. Hence, I need a new front mech. Can anyone tell me the size I need please. Its a standard road bike from the 90`s, down pull, double c/s, shimano. Am I correct in thinking its 31.8?

 

[PpPete]

more likely 28.6 IMO

 

[paul white]

Thanks, I`ve tried measuring it, but not confident of size

 

[PpPete]

One of the most useful bike tools if you are playing with old bikes:
http://www.ebay.co.uk/itm/6Inch-150mm-Digital-LCD-Caliper-Micrometer-Vernier-Tool-/280788210990