New 4 piston calipers

[Treetrimmer]

Hi All,

I have taken the plunge and purchased new 4 piston front brake calipers, supplied by Zeus in the U.K. These give a greater pad area, plus greater pad pressure, to help modernise the braking performance.
I was a bit peeved to subsequently find I had to make alterations to the Stone guards, but more importantly the new calipers offer the possibility of 1/2" discs, compared with the standard 3/8" disc. I believe the 420 had 1/2" thick discs as standard; is anyone here able to confirm this? My original discs are quite corroded, as the car has been standing for some time, so it seems appropriate to have new discs to go with the new calipers.
The Zeus calipers come with a variable shim arrangement to allow for the choice of 3/8" or 1/2" discs.

Regards, Richard

[cass3958]

Not sure about the sizes but the 420 part number for front discs is C27024 where as the S type part number is C23484.
The 420 have a three pot caliper system (2 on the outer caliper and 1 in the inner) where as the S type only has two pots the same as the Mk2.

[JCS]

Richard

Both the front brake calliper conversions by Cooper Craft and Zeus require modification to the “stone guards”.

The front brake hose outer mounting point is part of this guard. It is possible to successfully modify the shield, and presumably fashion a new hose mounting bracket if needed. Care needs taking if the steering has been converted to rack and pinion steering, if lock stops have not been fitted. In that condition the shield can become trapped between the brake disc and the top suspension joint on full lock and because of the weaken disc it can be ripped away.The fouling of the shields is also very much dependent upon the positioning of the castor angle shims.

These “Stone Guards” were fitted to equalise the disc pad wear, not particularly to combat rocks. Given the low annual mileage of these cars today you could contemplate removing the shields and fitting a different front brake hose support.

Unless you are contemplating some serious Alpine fast motoring I would suggest keeping to the original disc brake thickness. The brakes on these cars are up to the job particularly after a Coopercraft or Zeus conversion. Do keep an eye on the brake fluid level and be prepared to replace the master cylinder and servo. With the conversion the piston travel in these units can increase. These conversions are much better completed on the S Type than the Mk 2 due to the loaded centre of gravity position on the car.
Norman

[Treetrimmer]

Hi Norman,

Thank you for your comprehensive reply.
Judicious use of a "Dremmel" type tool, and plenty of " offering up and checking" means I've managed to successfully adjust the original stone guards, and still retain the original mounting point for the brake flexible.
The "1/2 inch" discs I purchased from David Manners were part number C27024/1. They are slightly less than 1/2" thick, but substantially thicker than the rusty original ones. Strangely, they were somewhat cheaper than the standard 3/8 " thick discs.
I note your comments about the brake master cylinder, I hadn't considered the greater piston travel required, so I think I'll replace the master cylinder for peace of mind.

Regards, Richard