Front aftermarket caliper

Hi, I have an 850 Mk.3 I am doing up. It has an aftermarket AP Lockheed front caliper on it. It needs new pistons & seals. Is this caliper a better alternative than the original?

Hi Flozz
the ap caliper is miles better. You can buy all the parts from Andover Norton although they are not easily found on the website. Or Fowlers of Bristol. The caliper will have a number cast into it near the mounting bolts/ stud/ nuts.

I use this caliper with a bigger floating disc . It's ugly in comparison . Grimeca M.C. and braided small diameter hose with it all . Works better .

two comments;

1. check the diameter of the pistons - there was a version of that caliper with 36mm pistons made for Triumph twin disc kits in the early 80s. A couple of years ago I was able to get some 36mm stainless steel pistons from L P Williams. (I have the 36mm version of that caliper on my Commando)

2. when you order the seal kit, check that it includes the square section O ring that seals between the two halves of the caliper, not all seal kits include that item, it may have to be ordered separately.

The AP caliper has a piston diameter of 1 5/8" where as the original has a piston diameter 1 3/4" so the original system has a better hydraulic ratio, But, the AP caliper has pads with more area where as the original has pads that are slightly smaller in area than the pistons. Everything else being equal makes the comparison between the calipers to not much difference in braking. What makes a BIG difference is fitting a smaller bore Master cylinder. Sleeved original or new. You can also fit bigger disc/s (the bigger the disc the better the braking)
If someone marketed a direct bolt on caliper that doesn't use an adaptor plate but uses The AP size of pad (or something similar) and crucially the original size of piston and disc, I would buy one.
I dislike the adaptor plate that has to be used with the AP caliper. Ruins the looks in my opinion.
The cheapest way to a better brake is the RGM sleeve kit for the master cylinder.

daveforty said:

two comments;

1. check the diameter of the pistons - there was a version of that caliper with 36mm pistons made for Triumph twin disc kits in the early 80s. A couple of years ago I was able to get some 36mm stainless steel pistons from L P Williams. (I have the 36mm version of that caliper on my Commando)

2. when you order the seal kit, check that it includes the square section O ring that seals between the two halves of the caliper, not all seal kits include that item, it may have to be ordered separately.

Click to expand...

The 36mm piston diameter in your caliper makes for a far worse hydraulic ratio than the original calipers piston diameter of over 44mm.
Are you using a double disc set up? Or is that caliper on the rear wheel?

dobba99 said:

The 36mm piston diameter in your caliper makes for a far worse hydraulic ratio than the original calipers piston diameter of over 44mm.
Are you using a double disc set up? Or is that caliper on the rear wheel?

Click to expand...

Single 12" Norvil floating disc on a standard front wheel. The master cylinder is sleeved down to 13mm. I think that makes a 15:1 hydraulic ratio, so not as good as the ideal which I believe is between 20:1 to 30:1? With HH disc pads it works OK. I do have a 'spare' alloy caliper with 41mm pistons, that would result in a 19:1 hydraulic ratio, so maybe worth a try.

Ratios discussed here with table


27:1 is supposed to be the sweetspot but this does not take into account the master cylinder lever ratio.



Post 18 in this thread has the full calc including lever length and offset

daveforty said:

Single 12" Norvil floating disc on a standard front wheel. The master cylinder is sleeved down to 13mm. I think that makes a 15:1 hydraulic ratio, so not as good as the ideal which I believe is between 20:1 to 30:1? With HH disc pads it works OK. I do have a 'spare' alloy caliper with 41mm pistons, that would result in a 19:1 hydraulic ratio, so maybe worth a try.

Click to expand...

Looking at the chart posted by Kommando getting the ratio up towards the low twentys is very benefical. Your current set up hydraulically, is no better than a bog std system (5/8" m/c, std disc, std caliper, rubber lines)

I've recently bought a genuine Lockheed seal kit and some stainless pistons from this place.


Very fast delivery and the pistons look to be great quality and fit perfectly. Some of the newer calipers have alloy pistons but mine had steel chromed ones that were a bit messy on the outer edge.

I use 2 Lockheed AP calipers on Suzuki high speed steel discs with a master cylinder which is designed for use with only one AP caliper. I had trouble getting pads for it. But with very old asbestos pads, the brake is one-finger operation and excellent. On a race bike, the front brake can be a major source of anxiety. It is the thing which is most likely to bring you undone. What I really like about it, is it never changes.

AP clone, bigger disc, and 13mm MC here. Makes for very acceptable braking for me.

Funny when I hear comments from guys who say "those things never had disc brakes" when they see the obvious new brake. I point to the rear and ask them to explain the stock brake.

I have a Rickman I’m rebuilding that has AP Lockheed CP2195 calipers front and rear, I’ve just stripped them and ordered seals, pistons and bolts. I’m not sure if this is the case with the later CP2696 caliper but in the earlier calipers I have the pistons are different heights one being 0.700" and the other 0.820". Only problem is I can’t find a torque figure for the bolts that join the two sides of the calipers together but I’ve emailed AN, who I’ve ordered the parts from, for the figure.

Dave