I want a smaller front cog - not sure what I have
Discussion
You need to measure the bolt circle diameter (BCD): details here http://www.sheldonbrown.com/gloss_bo-z.html
You can then look for rings in that size. IIRC the BCD on older cranks may not allow much smaller than a 42t chainring so you may be better off changing the rear cogs for a larger range.
You can then look for rings in that size. IIRC the BCD on older cranks may not allow much smaller than a 42t chainring so you may be better off changing the rear cogs for a larger range.
Hi Tobinen,
That looks like a 135 BCD so you're stuck with a 42 tooth inner ring with that crankset.
Now, there are plenty of ways to get a compact crankset on that bike but I'm pretty sure you're going to have to put a new bottom bracket on as well, to get a JIS square taper spindle.
I think you have ISO on there now which vastly reduces your options as far as compact crankets are concerned - they will sit too inboard on the spindle and the bolt will bottom out.
I had this exact situation on my Olmo. I swapped out the Campy 53/42 crankset and BB for an FSA Vero 50/34 and a Shimano ST BB. Make sure you order the BB with correct threading! Mine was Italian threaded. You'll know by checking the BB you remove, it'll have thread dimensions on it and Italian is righty tighty on both sides!
http://www.bikeforums.net/classic-vintage/773449-o...
That looks like a 135 BCD so you're stuck with a 42 tooth inner ring with that crankset.
Now, there are plenty of ways to get a compact crankset on that bike but I'm pretty sure you're going to have to put a new bottom bracket on as well, to get a JIS square taper spindle.
I think you have ISO on there now which vastly reduces your options as far as compact crankets are concerned - they will sit too inboard on the spindle and the bolt will bottom out.
I had this exact situation on my Olmo. I swapped out the Campy 53/42 crankset and BB for an FSA Vero 50/34 and a Shimano ST BB. Make sure you order the BB with correct threading! Mine was Italian threaded. You'll know by checking the BB you remove, it'll have thread dimensions on it and Italian is righty tighty on both sides!
http://www.bikeforums.net/classic-vintage/773449-o...
Barchettaman said:
Hi Tobinen,
That looks like a 135 BCD so you're stuck with a 42 tooth inner ring with that crankset.
You can get 39t sprockets in 135BCD, I've got one on my Campagnolo chainset. If it is a Campagnolo rear derailleur you might be limited to how big a sprocket you can use on the rear as well. That looks like a 135 BCD so you're stuck with a 42 tooth inner ring with that crankset.
Ha! With my little legs, 10% gradients are bloody hard work (rule 5 I know!)
What about this? http://www.ebay.co.uk/itm/NOS-Vintage-Campagnolo-3...
What about this? http://www.ebay.co.uk/itm/NOS-Vintage-Campagnolo-3...
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