both my '70s bikes are 27" -> 700c conversions. the first was fitted with ird b75 side-pull calipers. the brakes work quite a bit better than the vintage dia-compes they replaced, but they look a little out of place. they're bulky. i was hoping i wouldn't have the same issue for the next conversion, but it's almost the same exact reach issue with this english bike (vs the frenchie). the rear on both needed an extra long reach (more than 62mm), and the front was about 55mm on both. there are a few options, including some really nice looking center-pulls. another is using a dia-compe mini bmx caliper for the rear. (search ebay for mini bmx dia-compe if interested. they look nice.) even though those ird b75s look out of place, i opted to go the same route on the english bike conversion. the good news is, harris cyclery sells tektro calipers individually, so i bought the r539 for the front and the longer r559 for the rear. yes, it won't appear as vintage appropriate, but peace of mind goes a long way the next time that truck pulls out in front of me while flying downhill...