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TOPIC: Question about KZ750/KZ550 rear wheels

Question about KZ750/KZ550 rear wheels 02 Dec 2019 18:37 #814858

  • Saablord
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I was thinking about swapping the rear wheel with drum brake on my 82 kz550 LTD for one with a disc brake. Partzilla link for current wheel
I found a 80 KZ750-H1 (LTD) at a local salvage place and it looks awful similar. partzilla link for KZ750-H1 rear wheel with disc

Both wheels are J16x3, and they share a axle bolt which leads me to believe the spacing between the chain tension adjusters is the same. Could this be a straight swap? Might have to machine different spacers? Id use the 550 swingarm with a caliper torque bar mount welded on as i believe the 750 swing arm is longer and has a wider pivot.

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Question about KZ750/KZ550 rear wheels 03 Dec 2019 07:30 #814872

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It might work. I put 550-Ltd wheels on my 81 650-CSR & it was a direct swap. The 650-CSR has the same frame as the 750H Ltd & they share a bunch of parts, including the swing arm pivot. I'm pretty confident that the 750H rear wheel will fit my motorcycle, so if it fits the 650-CSR then it should also fit the 550-Ltd. However, I think the 550 has a smaller frame & I have no idea if there will be any issues with that, such as the torque link mount or brake pedal linkage.

Other stuff. The 650-CSR has the same muffler stays as the 750H >> the RH stay has mounts for some of the brake stuff. The 650-CSR shock damper & sprocket carrier are the same as the 550-Ltd & 750E/H models, and they all use the same Rr axle. The 550-Ltd Rr hub is ~ 4-3/8" wide >> you could measure it yourself & get that same measurement from the 750H Ltd wheel. I have no doubts that the 750H Ltd wheels can be used on my motorcycle, so I bet they can be used on the 550-Ltd.
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Last edit: by martin_csr.

Question about KZ750/KZ550 rear wheels 03 Dec 2019 08:18 #814875

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Thanks, exactly what I was looking for. There were some topics on this but they were mostly on the non LTD 750s that had the 18x2.15 rear wheel.

Since this is an 80 750 parts bike, I'll take the jugs and head as well to put on the 650 motor in the bike already to make an 810cc "kz550". Should be fun.


Oh and I think I should be able to make the master cylinder mount work. I have a zr7 exhaust on this already so I have a custom mount back there for that anyways.

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Question about KZ750/KZ550 rear wheels 04 Dec 2019 19:44 #814926

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Hey Martin, nother silly question here... I started looking at the front suspension.... It looks like the front wheel and dual calipers should swap over! All of the wheel bearings and spacers are the same, but the wheel has a different PN (which makes sense for the dual disc mounts). The discs have different PNs, but should be the same according to the EBC aftermarket PN.

Anyways, any thoughts on that?

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Question about KZ750/KZ550 rear wheels 05 Dec 2019 03:31 #814935

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Typically with KZ brakes, the single rotor is much thicker than the rotors for a dual setup, so you should not run two single rotors, nor a dual rotor by itself. As long as you have the wheel, rotors and calipers from a factory dual disk setup, you should be fine.
Does your off-side fork have caliper mounts?

Edit: The master cylinders are also different.
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1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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Last edit: by TexasKZ.

Question about KZ750/KZ550 rear wheels 05 Dec 2019 05:17 #814936

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>>Does your off-side fork have caliper mounts?
It does.

>>Edit: The master cylinders are also different.
Hopefully I can find a rebuild kit for it. I had to use am eBay front master cylinder because I couldn't find seals for the 550 one.

Thanks again for confirming that. I'll post an update when I get the parts.

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Question about KZ750/KZ550 rear wheels 05 Dec 2019 07:18 #814941

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Dual disk rotors may be smaller in diameter, so the dual disk calipers are mounted differently on the forks.
The 550-Ltd single disk rotor is the same diameter as the 650-CSR & it's larger in diameter than the 750H Ltd.
I have a couple sets of 750H forks & the caliper mounts are indeed in a different location. I think lower on the fork legs.

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Last edit: by martin_csr.

Question about KZ750/KZ550 rear wheels 05 Dec 2019 10:38 #814955

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hmm. This was what i was going off of for the rotor diameter: https://www.kzrider.com/forum/5-chassis/474697-gpz-front-brakes#474704

"And an expanded listing of compatible disc's for several models(I believe the "K" listings are for EBC brake systems part numbers)):
Kawasaki Brake Disc Sizes
BRAKE DISC ROTORS:
Brake disc: KD1
FRONT Z250A3 Z400J12/J3 Z440D/H Z550A2/A3 Z550C1/C2(LTD) Z550D1(GPZ) Z650F2/F3/F4 Z750R1(GPZ) Z750E/L/H GT750-SHAFT VN750A"

I will, of course, test the 750 caliper on a 550, and measure the rotors before i buy the parts to be sure.

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Question about KZ750/KZ550 rear wheels 05 Dec 2019 11:31 #814957

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I would try the EBC site to verify what fits what. But I'm pretty sure the 750H disks are smaller in diameter.
Without doing an exhaustive search, the EBC disk on EB for the 550-Ltd has a different part number. none of them I saw had the dimensions listed.

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Question about KZ750/KZ550 rear wheels 06 Dec 2019 03:50 #814973

  • Rick H.
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I am somewhat confused by this reply. All things being equal, except for thicker rotors, why would it matter if a person ran two thick rotors or two thin rotors so long as the rotors are the same thickness? I can understand not wanting to mix two different thickness rotors on the front axle, but if they are the same width and diameter it shouldn't matter at all.

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Question about KZ750/KZ550 rear wheels 06 Dec 2019 06:56 #814977

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Kawasaki ran two of the thick single discs in the very early Z1, but changed to thinner ones. I suspect it had in part to do with rotating mass and unsprung weight. The extra rotating mass would partially offset the effectiveness of having two brakes, and thinner ones cool more quickly.
More unsprung weight is not what an already too soft suspension really needs.
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Question about KZ750/KZ550 rear wheels 06 Dec 2019 08:03 #814980

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I'm not sure what setup you're going for but here is some info regarding single and dual disks on the various Kz550's.

As mentioned in the quote, you can't really just put a dual disk wheel with rotors onto a single disk Kz550 and add a caliper. The disks won't align with the pads since the dual disks are smaller diameter. The options are to run two single-disk rotors on the dual wheel or get fork sliders from a dual-disk bike, or somehow make adapter plates and use different calipers. Or possibly get a pair of dual-disk rotors from a bigger bike. The single disk is indeed thicker than one of a dual disk.

It does raise the question why Kawasaki made forks with both caliper mounts if it also made dual-disks with smaller diameters.

Brake disks, and likely forks, depends on the year and location. There are a slew of different brake diameters for the 400/500/550 line.

The Kawasaki Factory service manual, uses the term "effective disk diameter" for it's measurements, which is not the actual O.D. measurement. From what I gather, "effective disk diameter" is measured from the center of the pad area.

From the factory service manual (red base manual 99924-1018-03):

1979 500B1 models:
Europe and Australia got dual front disks. They were 232mm.
Everywhere else got single disk. It was 250mm.
All had rear disk. It was 237mm.

1980 500B2 was the same 500B1.

The forks have bosses for calipers on both sides even if the bike only came with one brake. But the forks will be different from dual disk models because the disk sizes were different.

1980 400J1 model:
UK and West germany got dual disk 232mm.
Japan and elsewhere was single disk 250mm.
Rear drum.

1980 550A1 models:
Europe got dual disk 232mm.
Elsewhere single 250mm.
Rear drum.

1980 550C1 model:
European got dual disk 226mm.
Elsewhere single 236mm.
Rear drum.

1981 400J2
UK and West German dual disk 226mm.
Elsewhere single 236mm.
Rear drum.

1981 500B3:
All got dual disk 226mm.
Rear is 226mm.



1981 550A2 same as 400J2 single
1981 550C2 same as 400J2 single
1981 550B2 same as 500B3
1981 550D1 same as 500B3 (Actual O.D. is 260mm. Rear is 7mm thick, fronts are 5mm thick.)

The forks use different amounts of oil too.

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Question about KZ750/KZ550 rear wheels 06 Dec 2019 12:15 #814996

  • Rick H.
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TexasKZ wrote: Kawasaki ran two of the thick single discs in the very early Z1, but changed to thinner ones. I suspect it had in part to do with rotating mass and unsprung weight. The extra rotating mass would partially offset the effectiveness of having two brakes, and thinner ones cool more quickly.
More unsprung weight is not what an already too soft suspension really needs.


I agree with the supposition that more unsprung weight may have been an issue, but I think in the overall scheme of things it really didn't make much difference in normal street application. For the life of me I don't understand why Kawasaki didn't equip all the KZ's and Z's with dual disc front brakes except as a way of saving some money on the back end. Of course perhaps they were ahead of time by offering an optional dual disc brake accessory kit in order to make more money after the sale. Something that H-D has gotten real good at. Simply stated, take off parts that you can and ones people like and make them available in the accessory catalog.
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Question about KZ750/KZ550 rear wheels 06 Dec 2019 14:06 #814999

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Rick H. wrote: I am somewhat confused by this reply. All things being equal, except for thicker rotors, why would it matter if a person ran two thick rotors or two thin rotors so long as the rotors are the same thickness? I can understand not wanting to mix two different thickness rotors on the front axle, but if they are the same width and diameter it shouldn't matter at all.

Rick H.


Not that it would matter much for normal street riding, but after hard braking wouldn't thick rotors retain more heat than thin rotors and wouldn't that have at least a minor impact on the braking capability? I believe some race cars actually spray water on the rotors to cool them for that very reason. Ed
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Question about KZ750/KZ550 rear wheels 06 Dec 2019 15:33 #815002

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Great info guys, thanks. Ill take a disc off another 550 and the calipers off the 750.

I would like to upgrade the forks, but that's a bit hard to do without loosing height with all the gsxr etc forks. I'll probably just get springs and emulators.

As for the heat thing, yes, a thicker disc would retain more heat, but it would also take longer to heat up as it has more thermal mass. This is important due to only having half of the surface area for cooling as the dual disc.

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