Forum menu
Hi,I have 2 MTB XT splined chainsets and for the life of me can,t find replacement chainrings.Ime surprised as i thought Shimano stuff would be easy to source.Anybody out there know of any.cheers.
As an educated guess, i'd say you've measured the distance from one bolt-centre to the next instead of to the opposite, which would give you the readily available 104mm bolt circle diameter.
Current Shimano 4 bolt chainsets aren't 74 BCD. As per coatesy, its 104BCD for middle and outer and 64BCD for inner ring.
Thanks,i always thought you got the BCD by measuring centre to centre but forgot you multiply this by 1.4 or very nearfor a 4 bolt.Thanks for your replys.
Just googled it ,its centre to centre measurement and multiply by 1.414.That gets very near 104.cheers.
Its bolt circle diameter (i.e. the diameter of the circle that the bolts are on), the figure you mention probably is the multiplying factor but why not just measure between opposite bolts, passing across the axle centre?
Yes ,will do if that gives you the BCD.What about a 5 bolt,measuring between opposing bolts would not pass through the centre so not give you the diameter.cheers,thanks for reply.
Ok, so measure from bolt to centre of bb axle and double it works for any number of chainring bolts. The multiplier of 1.4...for a four bolt changes for five bolt to something like 1.7...(I had to google that one being too lazy to work out the maths 😉
That sounds like the easiest way,thanks.