Odd chainring size

cpeachey

I am re-building a Dawes tandem for a friend. The inner chainring is 5 bolts 47mm c-c making the BCD somewhere between 74 and 86. Can anyone give me the correct BCD for this ring please? Do you know anyone selling them?
Chris

pete.whelan

74mm is a size that is used for some chainsets.

At one time TA used to supply their chainrings with a cardboard inner , which on the reverse had a set of concentric circles and hole markings so you could determine the chainring size - another cyclist local to you might have one

mab bee

The bikeplus website has a scanned-in image of this cardboard sleeve -- just look in the chainrings section of their site

cpeachey

I have several TA sleeves but my spacing is not there. Cranks are marked CHINA.
I think a new crankset is in order!
Chris

maddog 2

see http://www.sheldonbrown.com/gloss_bo-z.html

nothing listed at 47mm c2c though.

Try spa cycles, and sjs. They have a wide range of odd stuff.

http://www.sjscycles.co.uk/

http://www.spacycles.co.uk/

paul_smith_srcc

CPeachey wrote:

I have several TA sleeves but my spacing is not there. Cranks are marked CHINA.I think a new crankset is in order!Chris

Check Chicken Cycles for what is made, for how the measure them these two diagrams may help, I made the first one and I scanned the second from a TA chain ring box.





Bolt Spacing Multiplied by 1.7 = PCD

PCD divided by 1.7 = Bolt Spacing

Paul_Smith
www.bikeplus.co.uk

nicklouse

nice bit of info here http://www.sheldonbrown.com/gloss_bo-z.html