AP Caliper CP3697 or CP2696??

Rgm list the normal CP2696 caliper as used by many owners of a hole range of classic machines. They also list a CP3697 which is said have larger pistons. On their old website it used to say that using the cp3697 with its larger pistons would maintain the hydraulic advantage gained from sleeving down the master cylinder. Does anyone use the CP3697 an can confirm this??

toppy said:

They also list a CP3697 which is said have larger pistons. On their old website it used to say that using the cp3697 with its larger pistons would maintain the hydraulic advantage gained from sleeving down the master cylinder. Does anyone use the CP3697 an can confirm this??

Click to expand...

If the CP3697 has a larger pistons, it will further increase the hydraulic advantage from sleeving down the master cylinder, not maintain the hydraulic advantage.

You need to cite the before and after master cylinder diameter as well as your current caliper piston diameter as well as the diameter of the two CP caliper pistons. Calculate the areas and then compare the ratio of your current caliper cylinder area to your current master cylinder area.

or

You can use the handy chart at Vintage Brake - http://www.vintagebrake.com/mastercylinder.htm

With the above chart all you need to know are the diameters.

Dances with Shrapnel said:

toppy said:

They also list a CP3697 which is said have larger pistons. On their old website it used to say that using the cp3697 with its larger pistons would maintain the hydraulic advantage gained from sleeving down the master cylinder. Does anyone use the CP3697 an can confirm this??

Click to expand...

If the CP3697 has a larger pistons, it will further increase the hydraulic advantage from sleeving down the master cylinder, not maintain the hydraulic advantage.

Click to expand...

I think the OP means the 3697 has pistons larger than the 2696, which, this seems to imply, are smaller than the OEM caliper?

I use 2 AP calipers and I've never checked they have the same piston diameters. Both of them are very old. I use the diameter master cylinder normally used for only one caliper and the brake is extremely good. I will check to see if they are stamped.

The piston diameter of the CP3697 and also standard Norton Lockheed caliper I believe is: 44.5mm.

The AP CP2696 piston diameter is smaller: 41.3mm.

L.A.B. said:

The piston diameter of the CP3697 and also standard Norton Lockheed caliper I believe is: 44.5mm.

The AP CP2696 piston diameter is smaller: 41.3mm.

Click to expand...

This is what I was lead to believe L.A.B. i have the RGM 13mm sleeve fitted an i can feel the standard LOCKHEED caliper flex ever so slightly when high pressure is applied (SS brake hose to). So force is being wasted but the norm would be to fit the CP2696 i do notice the picture of the CP3697 on RGM website show a more modern looking item than the CP2696 so it may be they are a newer product. For my money this looks the way to go i just wondered if someone has tried it.

A friend of mine fitted one of the 2696 calipers with the smaller pistons to a system with the standard master cylinder and one of the old Norvil discs with the serrated centre boss, he said it was much worse than the standard setup and immediately took it off. I have now inherited it and plan to use it with a sleeved down master cylinder from RGM. Does anyone have any experience with this setup?