@27motorhead do you know what the BCD on the crank on your bike is? I've measured and calculated the BCD on my crack to be 102mm?
Specialized Hardrock 1988?
- Thread starter Nog1988
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27motorhead
Old School Grand Master
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From memory middle & outer rings are on a 104mm BCD? I know they are different to Shimano’s 110mm BCD. Will get back to you later today
27motorhead
Old School Grand Master
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Sorry for later than planned reply. IGNORE what I wrote above. It's 110mm BCD like shimano esq chainrings of that era.
Remember with x5 bolts you cannot just measure between the centre of the bolts as they don't cross the centre line of the chainring as you'll end up with a false measurement. It's obviously different for x4 bolt...
See pictures for reference below.
110mm BCD should give you:
55mm from centre of BB to any of the centre of the bolts on the middle/outer rings/spider
64.5(ish)mm between the x2 closest centre of the bolts on the middle/outer rings/spider
104.5(ish)mm between the furthest bolts from each other on the middle/outer rings/spider
CLOSEST BOLTS (64.5mm-ish)
FURTHEST BOLTS (104.5mm-ish)
1/2 110mm BCD = 55mm !!!
Remember with x5 bolts you cannot just measure between the centre of the bolts as they don't cross the centre line of the chainring as you'll end up with a false measurement. It's obviously different for x4 bolt...
See pictures for reference below.
110mm BCD should give you:
55mm from centre of BB to any of the centre of the bolts on the middle/outer rings/spider
64.5(ish)mm between the x2 closest centre of the bolts on the middle/outer rings/spider
104.5(ish)mm between the furthest bolts from each other on the middle/outer rings/spider
CLOSEST BOLTS (64.5mm-ish)
FURTHEST BOLTS (104.5mm-ish)
1/2 110mm BCD = 55mm !!!
