If you can't get the recessed nuts through the back of the brake bridge/fork crown then, as far as I know, you won't be able to find anything thinner that might fit. What you'll need are a pair of nutted brake calipers instead, where a nut tightens AGAINST the brake bridge/fork crown, rather than inside them.
You won't just be able to sub out the recessed nuts for ordinary nuts on these calipers as the centrebolt lengths would be different. You'd be able to fit the front one to the back that way, but would need a new caliper for the front.
If this is the case then your best bet would be to buy a pair on here or retrobike or ebay. Weinmann produced plenty but of mixed quality, in my experience. Dia Compe and Universal also made loads of models, and of a generally better standard than Weinmann (but there are still some bad ones so try to look up model no. if you can).
Your best bet would be Suntour, Shimano, or Campagnolo calipers. They only come in sidepull but with some decent brake pads (Kool Stop Salmons, SwissStop blues, etc) they'll stop you no problems!
It's a bit of a work-around! But just for reference I'm running Suntour Superbes retrofitted with the new centrebolts and with SwissStop blues and they're stopping me on my loaded tourer no problems
Lovely frame!
Maybe it's a case of nutted vs recessed calipers?
Sheldon, as always, to the rescue: http://sheldonbrown.com/calipers.html
If you can't get the recessed nuts through the back of the brake bridge/fork crown then, as far as I know, you won't be able to find anything thinner that might fit. What you'll need are a pair of nutted brake calipers instead, where a nut tightens AGAINST the brake bridge/fork crown, rather than inside them.
You won't just be able to sub out the recessed nuts for ordinary nuts on these calipers as the centrebolt lengths would be different. You'd be able to fit the front one to the back that way, but would need a new caliper for the front.
If this is the case then your best bet would be to buy a pair on here or retrobike or ebay. Weinmann produced plenty but of mixed quality, in my experience. Dia Compe and Universal also made loads of models, and of a generally better standard than Weinmann (but there are still some bad ones so try to look up model no. if you can).
Your best bet would be Suntour, Shimano, or Campagnolo calipers. They only come in sidepull but with some decent brake pads (Kool Stop Salmons, SwissStop blues, etc) they'll stop you no problems!
Another option, if you can't find any decent nutted ones, is to buy a pair of sidepull recessed ones, use the front one on the back, and swap the centrebolt of the back one for the long one of these http://www.ebay.co.uk/itm/Centre-Caliper-Bolts-Dia-Compe-880-890-1020-MX900-MX901-MX1000-Old-School-BMX-/111648095312?pt=LH_DefaultDomain_3&hash=item19febebc50
It's a bit of a work-around! But just for reference I'm running Suntour Superbes retrofitted with the new centrebolts and with SwissStop blues and they're stopping me on my loaded tourer no problems
Anyway hope that's of some help