shimano exage 400ex cranks

i have come across a bike with these cranks on it, and was wondering if the ‘bio-pace’ chainrings that i have taken off are the original ( and there for can not be replaced) or if the og owner had replaced the old chainrings with the bio-pace? also what kinda quality frame came with this groupset? how do itell the bdc without mesuring ,is it marked on the inside of the cranks.?

You can change the Bio-Pace chainrings for any other chainring of the same BCD. You will have to measure to find the BCD though, won’t be printed on them.

Doesn’t matter if the originals are Biopace or not. The BCD is all that matters. Shimano Exage will be 130BCD

For a 5 arm crank, measure the distance between the centre of two adjacent chainring bolt holes and multiply by 1.7 to get the BCD.

And, in case you were wondering, for a 4 arm crank, measure the distance between two opposing chainring bolt holes and multiply by 1 to get the BCD.

cheers all. the first lbs to run some kinda workshop/lessons /bike maintaince course( 4wks 2hrs a wk) will not only develop a loyal following but sell heaps of stuff and connect a community in realtime ( not that i dont love you all here) . we do this with clients in the salon and rujn education nights and once word gets around it books out. I am sure there is some bike shop owners here somewhere. end rant…happily.

If you’re in Melbs, Total Rush does some courses, I’m not sure how advanced they are though.