How do I work out bcd

[jim55]

iv got a new chainset I bought of eBay for my single speed it's shimano 600 so matches brakes and stuff , only thing is, it's got a 50 tooth ring and I'd need to change it , so I'll look for a44/46 for it, but obv need to buy the right type , so how is it worked out ?
I've got digital calipers so can measure it properly

 

[midlife]

I'd hazard a wild stab in the dark and say 130mm

Shaun

 

[HarryTheDog]

http://guides.wiggle.co.uk/chainrings-buying-guide/
probably a compact so 110BCD most likely.

 

[jim55]

http://guides.wiggle.co.uk/chainrings-buying-guide/
probably a compact so 110BCD most likely.

Single chainring fitted but may have been a double in its past life

 

[Dogtrousers]

Sheldon to the rescue http://www.sheldonbrown.com/cribsheet-bcd.html

 

[jim55]

Cheers peeps it is 130 , off to eBay I go

 

[midlife]

130 BCD cheap as chips as companies like Stronglight make them as well as Shimano.

Shaun