strange chainring size BCD 78mm ?
08-15-10, 12:40 PM
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strange chainring size BCD 78mm ?
I bent my inner chainring (never mind how...), so I disassembled the chainset with a view to ordering a new ring. But however I measure the BCD, I can't find a match in stores on the web.
The bike is an MBK hybrid, about 20 years old and I think the chainset is original. The inner ring seems to have BCD 78mm (the middle and outer BCD is 120mm).
I'm not a bike expert, but I am an engineer. Can I possibly be getting my measurements wrong ? Or do I have an obscure and ancient fitting ? Does anyone recognise my plight, or should I just order a whole new chainset ?
I'm a long long way from a bike shop, so my only option for new parts is mail order.
Thanks for listening.
The bike is an MBK hybrid, about 20 years old and I think the chainset is original. The inner ring seems to have BCD 78mm (the middle and outer BCD is 120mm).
I'm not a bike expert, but I am an engineer. Can I possibly be getting my measurements wrong ? Or do I have an obscure and ancient fitting ? Does anyone recognise my plight, or should I just order a whole new chainset ?
I'm a long long way from a bike shop, so my only option for new parts is mail order.
Thanks for listening.
08-15-10, 12:47 PM
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What's the crank model?
Check here, it lists all BCD's . https://www.sheldonbrown.com/harris/chainrings.html
Check here, it lists all BCD's . https://www.sheldonbrown.com/harris/chainrings.html
08-15-10, 12:55 PM
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Thanks, Garthr, but that's just the thing. It's not on that list. The crank has "classic" printed on it and has 5 bolts. But the BCD is 78mm +/-1mm and the C-C 46mm +/- 1mm.
08-15-10, 03:17 PM
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Pictures speak volumes. 20 years ago chainring bolt circles were relatively standardized, but there were a couple wild cards.
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08-15-10, 03:50 PM
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