Superficial – I feel like you might have had something important to say, Neilwheel? Don’t leave me hanging.
Sorry about that, post drink posting, started writing a description, confused myself. Then went on a rant about standards, retro-fit and lack of compatibility, and then round it off by deleting the lot instead of editing.
You can fit A shifters to B levers but without the insert and cross bolt shown in the centre of the diagram above it is a faff.
You need to cut off the hooked spur on the A shifter bracket, so it is in line with the mating face but still has a tab on the top face to engage in the B brake lever.
The hole centres do not match between A and B either, so the the two mating faces do not fully engage and result in a wobbly shifter mount. The fixing bolt hole in the A shifter bracket needs to be slotted so the A shifter mount fits higher on the B lever and is solid when using the levers.
I then made some adaptors by drilling and cutting a thread in some aluminium bar, held in place with a small split pin, for the fixing bolt to attach to.
Hope that makes some kind of sense.
Obviously all this is very time consuming and unless you are desperate for new brakes or can find some of the special fixings going spare then you may want to save some effort and buy the adaptor kit if in stock.
Yes i think this really does suck a big fat one on Shimano’s part. (Rant removed.)
But I think there is now Ispec-C, or maybe it was just a dream.