2002 Cop Calipers - Twin Piston Upgrade

Just did some test fitting of my new rear twin piston caliper from a 2002 police bike, and I'm lovin' it. It was a direct bolt-in swap, but I'll need a slightly longer hose to hook it up.




I've got the matching fronts on the way, along with the master cylinder and forks to mount them up.

You have my attention!
Although I think the twin piston calipers would do more good on the front than rear,when youre getting on the skids really hard your weight is shifting to front of bike making rear wheel really easy to lock up from lack of traction.
I wonder if fronts will be that easy to change over?

Heres the fronts

As long as you can use them with the older rotors this could definately open lots of doors braking wise.

I know the rotor part numbers are the same between the '02 and my '81 GPZ, so that should be a go. The fork lowers are definitely different, so I got those coming also. I'm just hoping the spacing between the forks is the same. If so, I should be golden.

I haven't given up on this, just haven't had much time to tinker lately.

I got a 2001 ZR750 rear master cylinder bolted in and a custom line made up, so the rear is basically done. The front is going to require a little bit of machining to fit, though. Apparently the fork spacing on the police bikes is a little wider than my '81 GPZ, so the calipers hang a little farther away from the fork to reach the disc. Once I mill about .200" off the shoulder of the mounting tab, everything should go together nicely. I'll post some pics later to explain exactly what I'm talking about.

Have a look at this website from the UK. www.pretech.co.uk

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ :sick: :woohoo:

Well, it's official. I'm an idiot. :pinch:

When I checked rotor part numbers, apparently I only checked the rear, because the fronts are indeed different.

I cut down the mounting ears on the forks, put fresh seals and fork oil in them, and bolted everything together. It didn't take long until :huh: "Something doesn't look right."

The pad is only contacting the outer half inch or so of the rotor. After looking at pictures and measurements on the web, it looks like the police rotors are about an inch bigger in diameter. And, even better, they make the extra diameter by enlarging the center hole, so the bigger rotors won't bolt up to my wheel. Aaannndd, best of all, I don't think the hub of the cop front wheel will fit between my forks, because I got the front axle from the cop bike, and it's almost an inch longer than the one from my GPZ. I guess the forks are spaced farther apart and a wider wheel goes between them to make up the difference.

Nevertheless, I will not be defeated. I'm too hard-headed for that! I believe it will be easier to mill up some mounting plates to adapt to my original GPZ forks than to try and use the cop forks.

However, I think I need a break from this project. I think I'll get back to re-assembling my engine, and tackle this little gem a little farther down the line.

Are those actually gpz1100 fork legs?

No, what's pictured is the cop fork I was hoping to use to make this basically a bolt-on upgrade. Looks like I won't be that lucky.

Id try the gpz lower legs and see if its closer