Grinding and Drilling brake rotors

Everyone who needs their old rotors drilled and ground needs to read this. Yesterday I found out about a guy about an hour away from me named Tom. He has 25 years of grinding experience and owns truedisk.net. He used to make the diamond tooling for the grinders that he uses on the rotors. I'm not exaggerating when I say he is the real deal. I drove down to his place today and watched the whole process. Not only does he do great work but he is also a very genuine guy. He charges 45 to straighten out and regrind a rotor and 25 to drill any design you want as long as it's safe. He does all the calculations right there. Go to his site for more info on how to ship your rotors to him. He can do any rotor besides the big buel ones. He also told me that the people on eBay who use Blanchard grinders are doing it wrong and it won't take the warp out of your rotor. He always measures the runout before and after the process to make sure everything is straight and true. Send them to him and you won't be disappointed. Pics of before and after of my cb500 rotor

That's a good lookin' rotor!

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.

SO - how do we get in contact with your friend? http://www.truedisk.net/ -?

Awesome!

-S.

I have used True Disk a couple times. Very reasonable prices, quality work, and quick turnaround. what more could you ask for? The last set of rotors i sent him because i was experiencing a wobble from the front. He figured out one of the rivets was coming loose and he re-peened it for me.

That's a BEAUTIFUL disc! But WTF is it from? It's a full nine-rivet type, obviously Honda, but it's got a four hole bolt pattern? Would that be from a later CB400 or CB550? Please excuse my ignorance! I'm familiar with the nine-rivet rotors with six bolts, I'm familiar with the six-rivet discs with four bolts - but this is like their bastard step-child here. Very interesting indeed.....

Good to hear such positive feed-back. I've sent them an e-mail just now, gonna ship 'em some stuff! So ... thanks for the heads-up!

-S.

(EDIT!)

Post Script:

DOH! I just figured it out - that's Either a Suzuki disc or a KAWASAKI rotor! It's KZ, right? Got a couple of 'em from KZ1000A/KZ750B rear hubs, and front brakes on KZ400 & KZ440LTD etc. Of course Suzuki also had similar rotors but IIRC a bunch of 'em only had EIGHT rivets in 'em. Didn't recognize the center-carrier design. The question is whether or not the nine-rivet versions from Suzuki & Kawasaki are also transferable to the Honda stuff, or vice-versa etc....

-Sigh.

You guessed correctly it is the rear disk from a KZ1000A2. This is not the one they had to re-peen.

BTW for drilling holes, as long as your holes are not wider than the diameter of the disk you will increase surface area.

Ah - the KZ1000A - this is the Conical rear hub? I've grabbed a couple of 'em, from KZ750B, and have been planning to use that in my "CB900K0 Bol Bomber", it's just that I haven't heard back for sure from the spokes people about whether or not I can re-drill another rim to suit it, or what. I really like the hub, it's light-weight, and THIS might be interesting to you

The front Honda COMSTAR type rotors fit the center hole with one bolt-hole lined up perfect. A five-hole rotor on a four-bolt hub, so either of two ways to fix it. But it's a good solid fit. Unsure of the clearance ... I should measure up one of these later DOHC Comstar rotors just for reference... But it's the EARLY one I wanna use, from the '77-'78 CB750F 'cause that's a smaller rotor. It's either that, or an adapter and a CBR type modern rear rotor, something SMALL in any case. Light weight, petite - about 220mm-250mm. I dunno whether it's got too much off-set or not, that's the trick. Been looking all over for a rotor with the right bolt-pattern. Another couple of rotors I'd like to try are the CB350 little guy, or there was a small Yamaha 250-ish front rotor I'd seen recently which was a one-piece steel, whereas the Honda 350/400 type has the alloy center carrier. Either one of 'em, then cut down smaller to suit a caliper from something smaller. I've been thinking I'd like to use the existing caliper hanger from the CB900F, just cut down machined to fit an opposed-piston caliper. Just because it would look that much more like a stock Honda job. The trick is whether an opposed piston caliper will FIT between the rotor & the wire spokes - all the more reason to use something like the front Comstar rotor, 'cause of that extra clearance. ANYTHING to ditch some of that un-sprung weight, rotating mass, etc.

One thing about that wheel though - as much as I like other features, I'm a bit iffy about the composite construction with the chromed-steel flange stuck onto the alloy core.

I lost both of my bike projects in a total-loss fire two years ago. I've replaced everything, except for a good pile of NOS parts which I don't think I'll find again - not for the same price anyhow - but yeah anyway my KZ1000A/KZ750B rear hub was in the freezer at the time, so as to shrink a stuck bearing out (after torching the outer hub with the bearing shielded etc) and so when the whole place was burned to the ground, there was still that fridge (with it's upright freezer half, left-right 50/50 type freezer-fridge) still standing in the midst of it all. Next to a thirty-foot-tall freestanding brick chimney, and over top of a half-burnt wooden floor over a basement full of jagged timbers snapped steel & copper pipes and about six or eight feet of standing black water. Probably a pretty BAD idea to check the fridge to see if that hub had survived.

But I had put about a thousand hours into hand-polishing the damn thing!

So yeah I managed to get the thing out of there - it had survived because the hub managed to find it's way halfway into a frozen TURKEY - which is odd because I'm a veg-head, but it was free with a massive TOFU purchase a month or two before. I had been planning to bring it to the men's shelter directly between X-mas and Thanksgiving, when people might wanna do something interesting with a Turkey. ANYWAY yeah, that Turkey seemed to have saved my hub. It must've been a massive heat-sink, when you think about it. Everywhere else stuff had melted, all of my NOS parts, some Borrani & Super-Akront rims in odd-ball yet desirable sizes, a Suzuki 4LS drum hub with all the trimmings, all of 'em melted into little Aluminum cat turd shapes. I should've polished 'em up & sold 'em. Set up a service "send me your beloved pet's last turd and I'll cast it's replica in Aluminum" then pick one out that looks similar.... And there was even another couple of hubs in the freezer which didn't make it, which had melted to some degree or another.

So I thought I was gonna be able to still USE this KZ conical hub, and I set about scrubbing it in the sink (once I was properly settled in elsewhere) what with all of the charcoal remnants of frozen mixed vegetables stuck all over it's surfaces, little bits of burnt turkey meat stuck hither and yon.

But when I got to scrubbing around the chromed-steel flange ring, it just POPPED RIGHT OFF! Keeping in mind there was no damage to the metals themselves, there was nothing left between the two parts but a little bit of blackened carbon, as though there was a smidge of EPOXY in there, but it had burnt away. No indication whatsoever that it had been BRAZED together with any sort of silver-solder or the like. As such I worry that even the replacement hub which I bought, won't hold together under really hard use.

Perhaps - if it doesn't mess up any heat treatment to the alloy hub core, maybe the fire-damaged hub could be brazed together with some silver solder. OR, I was thinking maybe a new flange could be made from Aluminum and welded into place. Not sure if that would work well with the figure-8 type spoke holes though.

Well - in the mean-time I've got ANOTHER 4.25x18" rim this time drilled for the CB750F-SOHC rear hub, which is heavy as a boat anchor, and limited so far as taking a smaller rotor etc - But it's an easier swap, being able to take most all of the original bits & pieces from the original axle, spacers, caliper & hanger, even the rotor with a few mods. I guess when I'm finally able to use the KZ's conical rear hub, or perhaps even lighter hubs like a front hub with bolt-up cush-drive, THEN I can sell off this extra rear wheel to somebody who has another DOHC Honda - unless I feel like building yet ANOTHER DOHC-4 Honda. Truth be told, pretty much everything I wanna build from here on in, revolves around drum brakes. I wanna build a light-weight CB750C/CB750K café but with a huge Fontana 250mm 4LS drum up front, rather than swapping it's rear drum for a disc brake, and it's single-disc for dual-discs. I guess a MUNCH 270mm 2LS drum would be acceptable too. A 230mm 4LS seems inadequate for a bike like that, 'cause I'd wanna ride the balls off the damn thing. I've dreamed of a bike like that for ages, and I guess I would wanna swap it's rear drum, for a slightly smaller lighter drum - but I've got a nice pair of alloy rims for the thing already so it's more than likely it would just be a stock rear drum and a dual-disc front end. Until I could afford a Fontana hub (sell a complete bike? Sell off my pain meds? Sell my ASS?) and I guess I'd need a new front rim too. But I've already got a pretty choice 3.50x18" Super-Akront for the rear wheel, and that's drilled for the OEM size of hub. (Which sadly won't work with silicone-sealed tube-less mods, 'cause it's a really old rim without the bead retention ridges!) Sucks to use such a heavy rear drum, but it's okay, 'cause the rear drum plate on CB750C & DOHC CB750K seem to match pretty good with the Fontana 4LS, they've got the same raised lines in a similar style, like that rear drum was copied from it or something. Damn though, that would be one cool CB750C/K/F light-weight single-seater. Maybe I can grab hold of some type of "Tu-Bliss" system - but sadly they're only made for up to 2.15"/WM3 width rims - 2.50"x18" might work up front, but the rear 3.50"x18" is a bit of a stretch.

ANYWAY - I really like that KZ1000A rear conical disc-brake wire-spoke HUB! Awesome stuff. When you consider how many other KZ cush-drive sprocket-carriers ("coupling-assembly" in Kawasakese) which are taller/wider of a "top-hat" and as such can move the chain-line out pretty much wherever you want it to be (with some milling back down) then it's a great hub for sticking wire spoke rims onto pretty much ANY bike I can think of. Would be neat to see it done on a ZX11 or some such.....

Yeah its good hub considering the time period its from. I never really questioned how the steel part was attached. I wonder if the fire did something to make it pop it off? Ive never heard of that happening to anyone. Like with most rims, it would have to be specifically drilled to the hub, especially because the hub is conical so the spoke angles are quite different side to side. Ive heard tale that you can sometimes over drill existing spoke holes and use fatter nipples to use a rim that is already drilled. I got stainless pokes and a excel rim from buchannons for mine. weighs quite a bit less than the factory mags that were on the 1000 when i got it.