Originally Posted by
Jeff Wills
In my 40+ years of working in and around the bicycle industry I have never seen a 27-tooth chainring. It might exist but it would be a very very rare bird indeed.
TA made 27T rings for the "Cyclotouriste" crank; my wife has one on her bike. I don't know if they're still made. TA also used to make custom rings in any tooth count; mostly very large, often used for those land speed record attempts. I don't know if they still offer that service.