Question about KZ750/KZ550 rear wheels

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.
Rick H.

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

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.

I pulled the parts off a week ago or so. Looks like the front and rear wheels will drop right in. I also tried one of the 750 calipers on a 550 at the junkyard and that seemed to line up as well.

I did not see a difference in thickness for the 550 and 750 rotors, but the 550 single rotor was larger in diameter than the dual 750 rotors. So I got another 550 front rotor.

Will be a bit before I can install these

I needed to fix a fork seal so i guess im going to swap these parts in.

As i thought I can use a 750 wheel with two 550 single rotors (10.625" OD) and the 750 dual front calipers. The 550 rotors are required because the caliper mounts are higher up on the 550 forks. The attached photo is with the 750 rotors so the caliper doesnt line up.



Maybe ill swap the rear when i need a rear tire :laugh: