The crazy thing about the old mag wheels is how heavy they were, ALL of 'em not just the CMA's - I suppose the early version Morris rear mag, like you see on Goose's bike in MAD MAX ... what the heck let's see if I can't insert the vid to my post:
JUST BECAUSE!
So yeah - you can see from the close-ups that this was a Morris rear mag, with the bolt-up Cush-Drive ("coupling assembly" in later Kawasaki manuals) - However, even the early Morris mags whether we're talking about the ones sold as aftermarket OR the ones Kawasaki fitted to early KZ1000's (not sure which model - not the 'LTD, something much earlier - the MK-II or more likely the Z1-R, IIRC) and then later presumably they cast them under license under their house brand - was it ENKEI made their 7-spokes? I suppose I could go in the other room and look, or more to the point out by my back fence where there's a KZ 7-spoke on top of a pile of Aluminum I've been meaning to drag down to the recyclers' - most of it fire damaged - I'm pretty sure it was ENKEI -
What a bunch of boat anchors, either way! Which is my POINT I'm trying to make - 'Cause the Morris Mags were Aluminum! "Mag" might connote MAGNESIUM but in the vernacular it tends to mean "wide" or more generally to any type of cast wheels. And let's make no mistake, pretty much 100% of the "mag" wheels sold for STREET bikes were made from everyday run-of-the-mill ALUMINUM!
Which is really just the one reason why they were heavy as #$%*, of course.
They were intended as an alternative to OEM rims which were chromed-steel & had to use INNER TUBES. By the way, for those who own an older Guzzi with mag rims which state "not for tubeless tires" this is what it's all about - it isn't about porous castings or anything else like that (which would be as simple to fix as laying a coat of paint inside the rim) - What's even funnier is that the same amount of Aluminum as it took to cast "not for tubeless tires" or "tube tires only" etc, they could've made 'em work - it's the ridges inside the rims, a half inch from the outer edges, which retains the bead of the tire even when the tire is flat. This is why tube-tire blow-outs are so much more catastrophic too, is that without a bead-lock (fitted as standard on several Kawasaki steel rims, two per rear wheel!) The deflated tire can now slip off the bead area and right off the rim itself if there's any lateral pressure at all - and there often is!
So yeah, the BETTER of the mag wheels added that ridge inside, but there was still a fundamental flaw, which I supposed was addressed by the COMSTAR rims, as well as several other Composite rims especially the PVM's & Technomagnesio rims with the Magnesium center section and the Akront alloy rim bolted to the end of each spoke - the COMSTAR has a butt-welded extruded hoop which is thereby a work-hardened, ie forged in a sense, outer circumference which can thereby be FAR thinner relative to a solid cast "mag" wheel.
See, when you put a Lester or Morris or any other mag wheel on a scale, often as not they come out better than an OEM chromed-steel rim. But the majority of the weight savings comes from the HUB area - it's actually not the spokes at all, even though the wire-spokes are steel if you've ever disassembled a Comstar or carved up a broken mag wheel (I did just that with some fire-damaged KZ stuff as well as Comstars intended for modification) the alloy in the seven-spoke mags amounts to the same weight or even slightly more than the equivalent steel wire spokes. However when you look at the drum-type mag wheels the drum area has just a thin skin of alloy around the drum linings. It's taught around the Iron and taught under the pressure of the spokes, but the point being that even a drum type mag wheel has less material in the center than the equivalent sized drum of a wire wheel - and of course it's quite obvious that the disc type mag wheel save substantial material in the hub area. This would account for the majority of that weight savings.
Of course, the other area which that savings comes from is the wire wheel having steel for it's rim, and then there's the INNER TUBE - which I'll get back to in a minute, or rather - I won't! Ha-ha.
But the fundamental flaw of all these mag wheels is in how the outer circumference is all constructed so heavily, at least - compared to an equivalent sized wire-spoked ALLOY rim! On the one hand that's because the material isn't work-hardened, though in the case of FORGED alloy rims such as modern Carrozzeria etc, I guess to some extent it IS - but still not quite as much as a proper butt-welded hoop!
There's also the way that the wheel is supported by 36, 40, 48, 54, 60, 80, 100 or even more, points of contact. Whereas in a seven-spoke mag, or worse still a five-spoke or even sillier a three-spoke mag -
(((Back in the day, that would've meant DYMAG - which were indeed Magnesium - check out Freddie Spencer's 1982 AMA Superbike winning 1032cc "CB750F" for some 16" front 18" rear DYMAG rims - or for that matter early Buell Battle-Twin rockets such as the infamous "Lucifer's Hammer" - the earliest ones had Dymags and hence benefited from some trickle-down COOL by association with the various Japanese fours which raced on 'em!)))
Those lesser spoke counts meant that there was this un-supported SPAN between the spokes, not only in danger of folding if you were to hit a curb let's say, but even in a sense just in terms of keeping a circular shape! This is why I'm so amazed by the Duck TT1 & TT2 limited edition models ... no wait, the Duck F1 I meant t say - the "Laguna Seca" and "Monjuic" ... actually I'm not certain which of the four versions bore them, but they had this 16" rims, and it's probably quite critical that this was only a 16" rim & as such the three unsupported spans weren't quite as long - with three-spoke Magnesium cores with an un-dimpled standard Akront (flatter type, not the "Super-Akront" rims I love so much) literally SCREWED onto the blunt ends of each spoke!
HMMM - was just looking 'em up to confirm exactly which Ducks I'm talking about here, and upon closer inspection MANY of these rims of which I speak appear to be a modified Akront "NERVI" rim, which like the D.I.D. rims on a Comstar, have a raised flange along the center-line (like a shouldered rim, but not on the shoulders - the "neck" perhaps?) The brand is MARVIC - however I've seen both types, the ones with the screws through from the rim's inside might not be Marvic brand but I know that I've seen 'em associated with late '80s / early '90s era Ducati limited editions, though I'm not sure they were all the Duck "F1"
Either way they're simply amazing, 'cause even in the case of the "necked" (half-shouldered?) "NERVI" type Akront rims, these Marvic rims have not just one wide cut-out, where the flange had been cut away, where they've situated the air valve along that center-line - not just one but THREE such cut-outs, so as to balance the weight I suppose - You'd think they'd get smart and drill one very tiny hole off to one side, and use those specialty mini-valves that the Italian bicycle guys use - not Schraeder valves, but ... "Presta" - the hole is waaay smaller. That way the ridge could remain continuous and the wheel would be a lot stiffer!
Anyway they're really amazing wheels, but I'd be careful not to hit any bumps with 'em!
(((I believe the "NERVI" would be an awesome rim to use in a rebuilt COMSTAR, for an extra wide rear wheel on an RCB replica, using a CB400T wheel-set, the CB900F rear rim or GL1100 front I suppose, in 2.50x18" is typically used to rebuild a CB400 or CM400 front non-reverse Comstar up to RCB specs, that much has been proven time and time again. However the big question here is whether the center-flanged Akront would have the correct inner diameter to bolt up to the Comstar spokes/blades/stars. Barring that I gather there was a 3.00x18" or 3.50x18" fitted to a Yamaha Super-Tenere 1200, which uses a center-flange design with reversed wire spokes, with the nipples in the hub - THAT might work out well with the Comstar rebuild. Alternatively yeah of course there are the Kosman weld-widened rims, there are some truly awesome projects on the DOHC 'F-orum which use weld-up rims such as member "MELCHIRO" who put a 5.00x18" black/reverse Comstar paired up with the 2.50x18" GL1100 front, on his CB1000F (CB750F with CB1000C engine, cases split and CB900F out-put shaft inserted - I'd be really curious whether that step could be avoided, and a BELT-drive replace the shaft instead of the chain!)
The thing about the weld-up method, which has been such a boon for the MAG wheel fans, is that it adds so much weight. Even though their usual donor rim is also an Akront. It's about that "row of stacked dimes" weld bead!
As such, methinks it might still be possible, if it turns out impossible to use the Akront Nervi rim, to use a standard non-dimpled Akront or any other non-dimpled rim, and bolt or braze-weld in some little TABS, machined to the required tolerances for the Comstar rivets and spokes etc.
Because that's how it was done by "Technomagnesio", they had a Marvic side-bolt type center-section, this time with five spokes that had Comstar style hollows running down their middles so I guess you could also think of 'em as a TEN spoke wheel if you like - they had five simple alloy chunks, cut from an extruded "T" profile, RIVETED to the rims, such that the center section might just as well have been riveted directly as with those other Marvic style rims.
Gotta dig up some pics of all this. One day I'll post a "treatise" on Comstars & other Composites. Why else would I have saved several pics of each and every single type or size of Comstar, pirated from their eBay listings? Why indeed ha-ha. But yeah, some pics would really help!
Any which way, all I'm getting at here, is I wish to illustrate what all is possible with a composite rim using an extruded butt-welded hoop. They really lend themselves well to some interesting purposes and some construction methods which folks might well consider SKETCHY!
One only has to wonder what might have come of the Comstar rims if the legal department hadn't stepped in and stipulated that they never be rebuilt. YEAH they're a heck of a wheel even as a throw-away to be replaced as a whole. But just imagine if they'd been rebuildable and different outfits could make rims under license, such that you could send off your Comstars to Buchanan's spoke & rim the same way I've sent 'em a dozen rims & a handful of hubs, and get back a perfectly balanced set with TIGHT-tight rivets, and rims on the order of 3.50x17" with 6.00x17", or 3.00x18" & 4.25x18" (Just like the wire-spoke Akronts they're building for me!) Surely, that's what was intended when they first drew 'em up on the board!
I guess I'll come out and say it then, just to bring this post back to ON TOPIC status, that my personal greatest piece of radioactive isotopic UNOBTAINIUM, would be the original bolt-up wide-as-the-plains Comstar rims from the 1976 RCB endurance racers!
Check out FACEBOOK of all places, for the Team Caillou Bedier RCB - they're rebuilding a 1976 racer all original in exquisitely delicious close-up macro-lens detail. Mmmmmm.....
This is what I'm talking about when I call ASTRALITE rims "the poor man's Comstar" - 'cause they might be expensive to obtain relative to a 2nd-hand (ie "free to carry away" ha-ha) Comstar rim, but if you spent half of that Astralite $$$ on the Honda wheel, you'd have the most awesome racing wheels IMHO. Of course, I'd wanna go with either a front wheel or a CB400T rear for five-spoke or XBR500 for a Boomerang, both drum types yeah but such small hubs it's just begging for a replacement hub in Billet - then a bolt-up Cush-Drive completes the picture, whether that's a billet hub or a front wheel it'll work either way.....
BAH! Enough about Comstars! What I'm REALLY meaning to talk about here is Mags vs Wire-Spoke ALLOY rims - not simply the compromise middle-ground between the two!
See, while the mag wheels were supposedly superior BACK IN THE DAY, though probably only on paper being that they might be 10%-25% lighter overall, they still carried 50% or more of their own weight in the outer inch & a half of their circumference - which is to say so far as rolling inertia the mags were very likely vastly inferior even to the OEM rims, provided that a light-weight inner-tube was used.
Of course, the lower overall wheel weight, of the completed assembly with tire - being lighter this meant that the un-sprung mass factor was superior ergo suspension compliance was likely far better. At the expense of braking and acceleration due to the rolling inertia problem.
There's a lot said about disc brakes being lighter than drums as well, but I'd be curious to see that stuff on the SCALES, 'cause I think people must've forgotten that the calipers & caliper hangers were also a part of the braking system, not to mention the hydraulics. Albeit, at least half of the hydraulic hoses plus the master cylinders, would've been sprung mass. But still mass nevertheless! I even wonder whether they also ignored the ROTORS themselves, as it seems to me that the disc-brake wheels were waaay heavier! It really is hard to say though, when it's so hard to compare discs vs drums on a one-for-one basis - certainly harder than comparing disc vs disc, drum vs drum!
Well whatever the case, the thing about these old wheels is a fundamental improvement to come along in recent years is that the alloy wire-spoke rims are no being produced WITH those bead-retention ridges I mentioned before. My old NOS rims I've been snapping up over recent years, they DON'T have 'em - as such they will always have to use an inner-tube. Until such time as it's worked out how to ADD the ridges whether in alloy or some other material!
Interestingly the old BMW alloy rims, the OEM replacement items (can't remember the brand but they're always associated with Beemers as they only came in Beemer drilling patterns) they didn't have the ridges however they had their own proprietary method which was a funny little divot between the spoke dimples where the drop-center inside the rim flattened out at this point such that the alloy runs straight across from one tire bead to the other. What this did, was it functioned as a RIM LOCK - the inner-tube valve functioned also as a bit of a rim-lock due to the large enough washer built into the valve & tube along with the narrow interior width of the rim itself - and on the opposite side from the valve there was this little divot. As such if and when there was a blow-out, the tire wouldn't slip off & wrap around the swing-arm & leave the bare rim to function as an ICE SKATE! Instead the flattened rubber tire stayed on the rim & made "flippy-floppy" as the song sez.
What's even more important than the bead retention ridges however, is that the dirt-bike kids have figured out that once a wire-spoke wheel is assembled and balanced, you can SEAL IT WITH SILICONE! If you're familiar with the "Team Incomplete" BMW Boxer (really trick frame modifications, in a sense like the "Wolf Rau" CB900F but also with the REST of the bike modded in sensible & functional ways, such that the Beemer Boxer is now a somewhat successful AHRMA racer. And yeah, their build-thread described how they used the silicone seal method and how they got fully five racing seasons, at the time of printing, with all of the tire changes implied by an active race team's use of those five seasons - without any leaks or delamination of the silicone seal!
Which is to say that while the SMART way to modify you bike back in the day was already to trade your OEM chromed-steel wire-spoke rims for ALLOY wire-spoked rims (on your old hubs OR alternative hubs such as a dual disc front or a lighter drum in the rear such as the CB500/CB550 rear drum in place of the CB750K 190mm boat anchor) - because even with some standard grade inner-tubes (let alone light-weight inner-tubes) in the wheels, the resultant product not only looked better (IMHO) not only functioned better - they also had far more legit racing pedigree than the cast-Aluminum "MAG" wheels everybody was into! Never mind the fact that this option was also LESS EXPENSIVE besides!!!
It's not just that good though, 'cause NOW you can seal them things up as tube-less with the silicone sealants! G.E. 1200 construction grade - take it from me, I used to build fish-tanks bigger than your bathroom, for a JOB not just a hobby, back in the 90s. Sheesh, I watch this show "Tanked" and I laugh at a lot of the crap those guys do. And I wish to hell we'd thought of going on camera back then. Well, not the BLACK MARKET smuggling of endangered species aspects of the job ha-ha. I worked for some rather sketchy guys down in Chinatown. Whom I suspect were also smuggling in some DRUGS as it happens. But yeah, we still should've done a book at the very least, or taken some photos if nothing else! I was doing some reptile handling for advertising companies too - that first Panther chameleon from the TELUS adverts might very well have been my work. Such a silly aspect of the job but the girls from that modelling agency sure thought I was macho. Did the maintenance on the tanks in their offices, so there was plenty of opportunity to flex one's muscles. Ah, but that doesn't even compare to the tour buses full of Japanese college co-eds.... ANYWAY YEAH - I know my friggin' silicone caulking. USE the G.E. 1200 it's the #$%*. Sez on the label that it causes sterility, so I never built any fish breeding tanks or reptile breeding terraria with it. Gave serious thought to casting vibrators out of the things - would've been a smart one for while my long-term sweet-heart was away at college. But then again, when they're away you don't WANT them to have properly functioning birth control. That takes away one very good way of busting 'em. And in the end, a sterility causing vibrator functions best when it's taking opportunities away from it's flesh-and-blood brethren! Even so, it would've sold like hot-cakes....
Enough masturbation.
I just wanted to point out everything that's screwed up about Aluminum mag wheels sold for streetbikes. ALMOST everything that is:
They're BUTT-FUGLY also! There. I've said it.
I don't mean to poo-poo on other people's tastes, I'm just sayin'. Much as they were "the business" back in the day? I would think that anybody who's spent the intervening years LEARNING a thing or two about bikes, would have come up with different ideas about what to put on a hot-rod and what not to.
-S.
