WOW that's awesome. I'm gonna ship him a couple of pairs.
I wanna make some rather special rotors here though. I'm sticking wire wheels on my CB900F, for a "CB900K0 Bol Bomber" look, which is what you call an '82 CB900F Bol D'Or done up as an homage to the '65 CB450K0 Black Bomber - get it?
Right now I've got the 296mm double-layered/vented rotors from the CB1100R on the bike, with CBX caliper hangers for proper off-set. So originally I wanted to stick 'em onto the SOHC type center carriers to run 'em on the GL1000 front hub - actually got the '78 CB750K front hub, which will look a lot more like the '79-'82 CB750K front hub but with six bumps instead of five. I guess these hubs are solid in the middle, whereas the older SOHC hubs, GL1000 hubs etc, are hollow in the middle. Shouldn't matter when I'm bolting up the stock carriers, but it's interesting if you're planning to re-drill the hub that's for sure.
So yeah, it occurs to me that the REAR rotors are ALSO 296mm - so if I have them riveted/bolted up to the front carriers, I'll have the older look and the lighter front end, but still with the 300mm-spec braking advantage. Should work just as well as running any 300mm modern rotors, but not as Butt-Fugly as floating rotors. Am hoping to use rivet kits they sell for the Harley "Juice Drum" which has it's sprocket riveted to the drum's circumference. If they're not big enough, I'll dig up something else.
There's a replacement rotor kit out there, which makes the drilling & resurfacing plus shipping seem VERY reasonable in comparison - "Metalgear AU" in Austria makes replacements which are very authentic. You could have the slotted CB900FC/CB1100R type rear rotor, for a SOHC rear hub, if you wanted. (ME I want something more compact & modern back there to tell the truth.) But what's INTERESTING about the replacement rotors, is that they only sell you the outer steel part not the inner carrier which is hard Aluminum alloy - plus some NUTS & BOLTS to assemble the whole thing with. I've seen a couple of bikes with bolted together rotors, using nylon "nyloc" lock nuts. But IMHO rivets would be better. Would help me sleep at night.
Either which way, I'm going with the classic SOHC style rotors on my DOHC bike. Even if I wound up running the DOHC rear rotors on the bike that's good - anything but the modern floating rotors. They're just as heavy as the OEM stuff, and the floating factor is superfluous when you're running floating calipers. IF you weren't aware of the CBX/GL1100A caliper hanger trick, or the 296mm front rotors at all, and you made DIY caliper hangers, then YEAH I could see why you might THINK that you need floating calipers. But it's not just that they're superfluous, that I've found another solution. It's just that the modern rotors are so damn ... BUTT-FUGLY.
I mean, let's face it - they looked good the first couple of times you saw 'em. But we're into CLASSIC motorcycles. And anything you take away from that well ... takes away from that!
I want the 296mm rotors, but I want the classic good looks of the drilled SOHC rotors.
Down the road, I wanna do something like the fake drum off the CBX550F, only I want it bigger. I also want a fatter fork, ideally something that looks like the forks on Freddie Spencer's Daytona winning AMA Superbike 1032cc "CB750F" in the Honda Collection hall - and what seems suitable for that would be the GL1500 front end: 41mm tubes, integral fork brace, 20mm axle, TRAC anti-dive, they look GNARLY as shit - awesome front end for a DOHC Honda!
What's more - check out the CBX550F front brake's air scoops. Incidentally, those little internal rotors are ALSO vented double-layer rotors. And they're not so much inside the hub, as they're tucked under those little plastic side shrouds with all the holes in 'em. Found some pics of the hub with those shrouds off, and the rotors stand proud of the wheel. So don't think of 'em as HIDDEN so much as ... hidden. Anyway yeah, a great little faux drum hub, but not on par with my tricked-out CB900F Bol D'Or or rather, "CB900K0 Bol Bomber"
I've actually GOT some 4LS Suzuki hubs here, one for the "KZ440LOL" I'm building for my teenaged Ex-Daughter, with 3.00x16" alloy rims and maxi-scooter low-profile tires, all NOS belt-drive, all sorts of cool mods - and hey the front end of the thing's a 39mm fork off the CB900F itself - had a spare planned for a 750, even planned to swap over the 750's 35mm-37mm fork to the little KZ. But then I bought the 900 and even considered swapping the 39mm fork straight across with some local 'F-er for the thinner forks off of THEIR bike! But then I weighed up the 39mm version and a burnt-out 37mm fork off my CB750F that got burned up in a house-fire - just prior to both of these projects being completed no less - ANYWAY the 39mm is only barely heavier than the 37mm version, so there's really no point in being that conservative.
I could see being that miserly with the weights - if I were running a SOHC racer, in the CB350F CB400F category, I'd consider running it with nothing fatter than the 35mm forks 'cause it would be over-kill to use the 37mm on that light of a bike. It's definitely over-kill for the KZ440LOL, it's just that THIS bike isn't gonna run on a track - not right away at least.
So yeah, I've GOT a 39mm CB900F fork with a GT750J drum adapted for it, and a spare center hub section - plus some T500 linkages & cams, the wider T500 shoes can be filed down to improve contact 12-14% so you want those shoes anyhow, the cams are the same parts, the linkages are different but they weigh like HALF of the 4LS linkages - Which is to say, a short trip to my machinist's and I'd have some useable side-plates for an entire 2nd 4LS hub which would work better than stock. Running an electronic speedo pick-up through the old cable sheath, in through a gutted out speedo drive. Which is to say, the DIY side-plates wouldn't NEED a damn speedo. They're better without!
But yeah - I might be crazy but not THAT crazy. The paltry 200mm of these Suzuki 4LS drums is barely adequate for the KZ440 - I wouldn't put one on an ultra-light DOHC CB750C/CB750K - let alone a tricked-out 900! I might see myself dumping a crap-load of money on a FONTANA 250mm 4LS and sticking THAT on an ultra-light CB750KZ racer, now THAT might just work. Dunno about the weight though, 'cause light as that hub may be, the single-disc DOHC wire hub is pretty damn light. VERY light rotors on these bikes. Like HALF of the weight of the SOHC versions. Which are half the weight of the CB1100R rotors.... Anyway - it wouldn't so much be about weight, it's just that the Fontana 4LS would be the most powerful brake for it's weight. There are equivalent brakes to stop a DOHC 750 with, but nothing would look so friggin awesome!
Unless of course there IS another option that might just cost less and stop better?
As I was saying - take a look at the air scoops on that CBX550F front hub. Now THAT would be one heavy-assed hub, if you used steel plates for the flanges, adapting it to spokes....
Then turn around and google the GL1500 Goldwing again! Especially the aftermarket light-up rotor shrouds, from Kuryakyn or Akrapovic or some such - they've got the exact same air scoops as the VTR250 & MVX250F, VF400F, CBX550F etc. It's a shrouded disc brake, with hints of a slightly earlier version of a shrouded disc brake.
Now I'm not suggesting that one should use the same shrouds as the GL1500, or even the aftermarket ones. I'm not even suggesting the GL1500 wheel have it's "Hub" cut out & laced to spokes. But take a look at the PC800 Pacific Coast now! That's the same "hub" as the GL1500, same brakes and stuff, only slightly different. THAT "hub" is practically ideal for cutting out of the wheel. Practically ideal for drilling for spokes. Whether they're drilled out of the sides, or better still drilled out of the out-most circumference/surface, and laced up with straight-pull "nail" spokes.
It would be a pain in the ass to design completely new rotor shrouds, but I think the end result would be awesome IF one could pull it off.
Now it's not quite the 296mm rotors that I've got the bike, but 286 is still 10mm better than the 276mm rotors which are OEM on the CB900F - so it WOULD be a legitimate upgrade brake. The 20mm axle in itself is a good reason to upgrade. These bikes, GL1500 & PC800 - they use the same axle as the CBR900RR if that's any indication. If you look into the notes on vintage Endurance racers built in the '80s, the consensus of opinion was that the axle was just as important if not MORE important, to front end stability - than the fork brace itself.
I dunno about whether it could still look like a legit faux-drum hub if you were to build some DIY rotors in the 296mm-300mm range, but if the existing 286mm rotors were replicated in CAST-IRON I'm sure this would kick ass. All of those old track bikes ran good Cast-Iron discs. The GOOD ones at least, the WINNERS did anyway....
The GL1500 version would be big enough for 300-320mm rotors, that is IF the thing could be laced up with spokes. But it would look INSANE - like an old MUNCH 270mm 2LS drum, only even BIGGER still. No, I figure the 286mm rotors are already gonna require shrouds the size of a 270mm drum from Kawasaki H1R or thereabouts. Bigger than the Yamaha 260mm drum I figure.
Ah well, that's long term. Like - for when I get a Tony Foale leading-link front end and build a "CB902" homage to the 1959 125cc CB92 Benly Super-Sport, or RC-142 racer!
-Sigh.