BRAKE SPECIFICATIONS AND COMMENTS
CB 450 brake: 200mm 2LS, 30mm wide,15mm axle, 40 hole, excellent internal-to- external leverage ratio, robust hub, cast iron bearing and actuating cam bores, long linings (more area than the 5mm wider Yamaha), shoes wrap around the posts, a pretty good copy of a Fontana. Two versions: one at 11lb. 2 oz; the other at 10lb. 6 oz. Clevises riveted on. The CB72/77 is similar, with 36 hole hub. Both use a stay mount. 42mm bearing OD make larger axle sizes possible.
Yamaha XS650: 200mm 2LS, 35mm wide, 17mm axle, 36 hole, good pre-holed hub and scooped backplate, swap bearings for 20 or 25mm axle, lug mount. 3 things not to like: wimpy 6mm link rod in compression, master and slave arms work through different leverage ratios, actuating cams do not locate shoes.
Suzuki T500: 200mm 2LS, 40mm wide, 36 hole, 15mm axle, the lightest of the "Big 3". Too light, apparently, as cracking seems to be a question of when, not if. Rusty Foard tested one of Tim's cracked hubs at the Naval Lab, and it only took 200lbs of side force to explode it. Rick Breckon welds reinforcing ribs in, but the bearing bore seems to suffer. Trick looking hub, dinky bearings lock you in to a 15mm axle. Okay leverage ratio, pressed-steel lever arms, lug mount, 4.5mm link rod. Lug mounts can be used on non-lug forks with a plate from fender mount to axle and attached lug.
180mm brakes--these can be made to work, but the leverage ratio of drum diameter-to-contact patch is real critical in this area. Best of the bunch is the CB160--a small version of the CB 450. The 180mm Yamaha is pretty good (see Jay), and the CB350 can work with some backplate blueprint work. I think the double sided 180mm SLS Grimeca is a bit of a toad. It's weighs 11 lbs., 2 oz., has just OK linings, and the brand new one I have in here, has extremely sloppy actuating cam bores. There does not appear to be ANY machined surfaces on the shoes or backplates, save threads. The axle and actuating cam bores appear to be as-cast, with attendant tolerances. Even the splines and thrust faces on the actuating cams look to be as stamped/forged. Most discouraging are the "dead" end of the shoes, which are only semi-parallel to the actuating cam faces.
That said, it can be made to work.
Aftermarket 4LS: 230mm Grimeca--Big bang for the buck, but at 21+lbs (a little less than a stock water buffalo), you better not care about turn-in. Stock shoes O.K. 210-230mm Fontana replicas (about 14 lbs in mag): Best-Dick Hunt, comes with 2520V available here; cheapest-Menani, needs relining, poor quality . Molnar--getting better, comes with 2520V. George Beale-comes with 2520V. Smith-Shoukai; heavy (AL), needs relining and rebushing, new.