Just replaced my 73 Shimano Bottom Bracket. Replaced what i think was a like for like 2.5mm spacer on the drive side. However, the chain seems to be catching slightly on the middle chainring before the mech and the chain length looks kinked.

Do i add one more small spacer or just add one larger to correct this?

Your spacers are right and shouldn’t be changed, check you’ve got the cranks fully home/in the right position.

Tapped the driver side crank in fully with a rubber mallet. Should I pull it out slightly then?

Are you refitting the same cranks as before or a new set? Are you sure it is home properly now and equally was before? Is it just catching the front mech?

Same cranks. Not sure about before, but i presume so. Drive side pushed right in too. When on small chain ring, chain seems to be catching on middle chain ring, before mech. Then on back peddaling on smallest rear cassette ring, falling off rear mech.

Is the front mech pushing it toward the middle? Even if it’s catching before it could be pushing it up?

I’d take the cranks off and refit as a starter and then you might need to adjust the front mech by the sounds of it. It is a bit odd tho.

Yep, chain just rubbing the side of the middle ring as it goes through the mech. First think i checked was the mech position but nothing catching there. Will refit crank and see what happens.

Is it a road BB, I gather that they are a slightly different width to the MTB versions.Also sounds as if you’re cross-gearing when you have the problem, never a good idea for this reason alone(also causes excess chain wear and too slack/tight a chain)