One thing I'm very curious about, is the fitment between the Harley front hub and the spacing for the brake rotors. First of all the bolt-circle pattern, and secondly on the spacing. Vis-à-vis, how does the Harley front hub compare to the Comstar five-bolt hub in these critical dimensions.
Another big question is whether the Harley hub adapts easily to the 20mm axle, whether it's easily adaptable to a 15mm axle, or whether those bearing sizes are outrageously difficult to find or expensive for that matter.
I gather you've GOT the 20mm axle on that fork. That's the same size on the GL1500 fork I plan to use, but in the meantime I'd also like to be able to use the 39mm CB900F fork on a 750 down the road.
Sorry, but I don't go in for the USD forks on Classic Superbikes - I could wrap my head around it if they're painted to match the bodywork, 'cause they'd look something like a shrouded fork on a CB350F, CB350K, or CB450K0 Black Bomber. But leave 'em in that sickly gold anodize treatment and they're butt-FUGLY ... IMHO.k
So yeah, while I'm after the 20mm axle, the 15mm axle still has it's place as well. Until I figure out modding the DOHC 15mm axle into a 20mm version, possibly clamped straight into the fork lowers....
Now I've already GOT some nice Honda front hubs, six-bolt dual-disc types from the '78 CB750K and GL1000 - but those are six-bolt, and I've got ideas about keeping my 296mm CB1100R vented type rotors.
But then again, that set-up would work just fine with either 296mm rotors from the CB750K0-'K6 in six-bolt configuration, or a more or less identical rotor with a FIVE-bolt carrier from the CB750A Hondamatic with the Silver Comstar front wheel and single disc brake. 'Cause those are also 296mm.
Here I'd thought that these CB1100RC/CB1100RD '82-'83 / CBX pro-link '81-'82 / '81+ GL1100A Aspencade rotors were the ONLY 296mm rotors from this entire era. Aside from the rear ones of course.
Now there's a dual-disc wire-spoke five-bolt HONDA front hub but it's exceedingly rare - it's on the Canadian model POLICE bike from '76 or '77, the CB750P7. I'd love to get my mitts on one. Would love to outfit that with some 296mm one-piece CB750F2 style rotors off the '81 CB1100RB - but they're BOTH very very rare parts.
So I figure I'll stick with the CB750K8 or GL1000 hubs, and six-bolt CB750K0-'K6 296mm rotors - and for the vented discs it probably makes more sense to swap out the CARRIERS than adapt a different hub. Seems like the simplest set-up.
I do think there's a good use for the huge thick vented HEAVY rotors from the CB1100R - picture coasting down from the top of the Great Divide between Calgary and Vancouver, especially on the Coquihalla highway which is basically a straight steep drop the whole way - you could leave the engine off and coast the whole way. Think I might TRY that actually. But yeah, all of that coasting on the brakes in gridlock traffic speeds, it all adds up to a lot of HEAT. And even where the extra surface area and directional vanes might not add up to enough air flow. But at least the HEAT-SINK factor from the extra MASS is gonna act as a back-up where the regular thickness SOHC rotors would've given out by that point.
Just sayin' - there are instances where you'd wanna keep 'em. I mean, the ENDURANCE teams had heard of too-heavy front wheels before. And yet they upgraded from the most perfect light-weight rotors on the CB1100RB, to the heavy-arsed vented type on the CB1100RC/D version of the racer. I think the heat-sink mass was the intent, and the extra surface area was added to help it out even further.
So yeah - I THINK I'd like to go forward with the six-bolt HONDA front hub.
However, if it's an easier time switching the Harley hub over to the 20mm axle, than it is to switch the Honda hub to the same 20mm axle, then it's not a problem to run BOTH versions of the five-bolt rotors on a five-bolt hub - alternating between the vented type and a pair of the CB750A Hondamatic version of the SOHC single-thickness discs.
So if that's an easier fix, I guess I can see myself using the Harley front hub. So long as it's laced with a Honda spoke pattern, with every other spoke bending to the OUTSIDE of the spoke flange.
If I wanted a really weird front hub with some #$%*ed-up spokes, I'm cooking up plans for a "Faux-Leading-Shoe" fake drum hub, using the PC800 Pacific Coast "hub" with that GL1500 fork. Or other 286mm rotor type forks such as VF1000R, which I gather is already a 41mm tube. Ah, but if I were after a 41mm tube TRAC fork and didn't care about the 15mm axle, I'd bet the GL1200 version would come at a better price. Nah - the big six-cylinder 'Wing already has the 20mm axle, which I gather is as huge an upgrade to the front end stability as a fork BRACE - possibly an even bigger factor.
I'd shoot for the 43mm versions from the CBR's but they seem a bit FUGLY to me. They don't seem "Period Correct" to the DOHC-four series.
And I figure a lot of these TRAC forks are a decent period-correct analogue for a SOHC bike as well, if you wrap your head around Honda developing some of that stuff for the early RCB's or the NR500 etc. I realize it probably never happened not even once, to see a SOHC 750 as a works Honda racer, fitted with a TRAC anti-dive fork. But it's nice to think that it COULD'VE gone down that way.
Heck I don't think they even appeared on the DOHC prototype RCB series, not until after the CB900FZ & DOHC CB750FZ had already come along.....
Anyway yeah - suffice to say, I really dig the TRAC forks, and the GL1500 version echoes of the AMA Superbike racers from AHM, Spencer's Daytona championship bike from '82, etc.
Even more important uses for the Harley front hub vs Honda front hub, or more to the point a Harley REAR hub, is I've got several rear rims drilled for the Harley pattern. But I wanna use 'em on the "CB900K0 Bol Bomber" and similar projects.
SO - my first impulse is to have 'em laced to the Honda FRONT hub, and use a bolt-up cush-drive. Ideally, with an adapted 260mm rotor from the CB350F/CB400F - 'cause I wanna adapt that same rotor to the bigger SOHC CB750F1 rear disc hub that I'm fitting to a couple of OTHER rear wheels first. In particular, I've got two 4.25x18" Akront rims, one drilled for the big Honda hub and one drilled for the Harley. And I'd like to get around to using the smaller hub so as to shed some of that un-sprung weight from my DOHC 900, as there's nothing bothers me more about the DOHC and SOHC four 750/900 as an entire bike overall, than that damn heavy-arsed rear hub!!! - So yeah, then the two main rims I've got for the bigger hub, (the 2nd being a Super-Akront 3.50x18" - though there are some others too I suppose...)- They could then be re-laced to a GL1000 rear hub or more to the point a weld-up combination of the drum with a shaft-drive center section stuffed inside. It's been done before and it's awesome. Thinking in particular of the VF750S/VF750C, or better still VF1100S/VF1100C. Got big ideas for one of these V-fours. Either way, there's a reason for keeping BOTH versions of these rims.
But if the Honda front hub is a hassle to adapt to a 20mm axle, this applies to the REAR wheel uses of this hub as well. 'Cause the 750/900 rear axle is ALSO 20mm. So yeah - if the Harley hub is a simpler job adapting to the 20mm axle than the Honda front hub, then it MIGHT be worth sullying my Honda flag-waving "CB900K0 Bol Bomber" with a Harley hub squeezed between the bolt-up cush-drive and the rotor adapter. MAYBE even one of the later era ... I think it's 2007+ ... Harley rear hubs with the integral cush-drive. Just so long as nobody notices!
It would have to be a significant advantage though.
Hey - as for those who are considering the floating rotors and other parts from the plastic crotch-rockets etc, there IS a good fitment for the SOHC six-bolt wire-spoke hubs, GL1000, CB750K0, CB750K8 etc.
The CBR900RR came in three different versions, across the 1990s - one of 'em had a 16" front rim IIRC - anyway it's the 2nd of those three versions which has a rotor bolt pattern which fits perfectly with the six-bolt wire-spoke hubs. Seems like you'd want some SPACERS, as the original rotors had more "dish" to 'em. But yeah, that's a 300mm+ floating rotor that doesn't need extraordinary measures to adapt to the hub. SFAIK those same rotors were standard fitment on other CBR's from the same era.
From what I've heard, Honda kept some pretty consistent rotor spacing from side-to-side, so I'd bet that set-up would fit to a lot of later CBR forks as well.
I guess I'm just a sucker for the Classic Superbikes - no question I can't stand the look of the Plastic Crotch-Rockets, not even a HINT of 'em.
Bothers the hell out of me that all of our TIRES these days look like crotch-rocket #$%*e.
They're made in sizes to fit all of the awesome classics, and yet they all have the same pattern of grooves/sipes on 'em, that became popular with the advent of the dayglow paint and the 17" three-spoke cast-mag wheels, fairings and tail cowls that look like Gumby's turds, horribly disfigured liquid-cooled motors twisted up inside of #$%*-storm frame rails of box-section tube....
-Sigh.
