Convert Kadett Front Drum Brakes to Disc's

[ultraclyde]

Well, work progresses haltingly on the '71, and I've encountered a new problem. I finally pulled one of the front drums, and all the brake hardware is shot. The springs are almost rusted through, the caps on the wheel cylinder were rotted out and the pistons inside the wheelcylinder were oxidized to white powdery lumps.

So, since I've got to TOTALLY replace all the brake components, how hard is it to convert the (manual) front drums on a '71 1.1L Kadett to disc?

Most of the hardware for the drums is readily available, but while I'm in there....

[BQS4]

Ultraclyde;
I'm not sure about the spindles, but, just to be sure, I'd find a GT and get everything including the spindle/knuckle assembly and swap to the much safer and upgraded disc brakes. Or go a step further, and upgrade to the 75 "big brakes" and really put some "whoa" to it!
Gene

[tekenaar]

Originally Posted by BQS4 Ultraclyde; I'm not sure about the spindles, but, just to be sure, I'd find a GT and get everything including the spindle/knuckle assembly and swap to the much safer and upgraded disc brakes. Or go a step further, and upgrade to the 75 "big brakes" and really put some "whoa" to it! Gene

OR . . . how about this , right here too!

[heimue]

It is the best idea to convert those brakes over to discs. As for the large discs, I would rate that as overkill. You have front drums now, meaning you have a "small" ohv engine - regular discs will be more than enough (or call it "just right"). You might have to change out more than only the spindle and the actual brake parts if you convert to discs from a "large" 1.9 liter axle. I did it once, but I don't remember what parts needed to be changed. And, last but not least, you have to watch that you use the right master cylinder and booster. It would be best if you had a donor vehicle to take all parts from, everything else can open a whole can of worms. But again - it is absolutely worth it!
Good luck, and keep us informed!
Dieter

[GTJIM]

I recently was working on my 1967 Kadett front disc brakes - they clamped on during braking and had to be removed to get the car home on the hand brake! Thought "I will just fit my spare pair of GT calipers and hoses". They do not fit - the mounting bolts are larger and spaced further apart on the GT ones. If you want to fit GT discs to a Kadett then the entire spindle will have to be replaced too. Later Kadetts may have different spindles that have caliper mounting points that are similar to GT ones but the early Kadetts certainly do not.

[anastosmotors]

I convert my 69 kadett from front drums to rotors.
i bought front spidle ass, [ w/caliper, rotor, steering arms, back plates,...]
i clean everything and rebuilt calipers. i never change
master cyl or booster. I do have the bigger lower ball joints.
it was an easy bolt on conversion. Car stops nice and does not
pull right or left when i stop.
I bought everything from dave at www.opeljunkyard.com

Pete

[oldopelguy]

The reason you had problems was because you have a 1.1 Kadett, Jim, not because it's a Kadett. The 1.1L Kadetts do indeed use a different and smaller caliper than the 1.9 cars, however the rotor and hub are the same. In fact, you can get the hub and rotor from pretty much anything pre-75 and it'll probably work, be it Manta, Kadett, or GT.

That said, you will need the spindles and calipers, as a matched set, from either a Kadett or GT with disc brakes. Either caliper size will stop the car fine, but if you go to the larger 1.9L calipers, you will probably want to add new larger wheel cylinders to the rear brakes as well to keep the front brakes from locking up prematurely on you. With a set of 1.1 calipers you can use the origional master cylinder you currently have, but you will need to remove, disable, and reinstall the residual pressure valve for the front brakes or they will "drag" on you and wear quickly and demolish your fuel economy, at a minimum.

The residual pressure valve on the Kadetts is on the master cylinder itself, the little brass adapter-looking thing that screws into the master cylinder that the brake line screws into. If you take it apart you will see that it is a check-valve assembly, and all you need to do is remove the little ball and spring from the one inline with the front brakes and you will disable it's functionality. It is there to keep some pressure, 8# by spec, in the brake lines for drum brakes to keep the wheel cylinders full of fluid and sealed against their bores while the springs for the drum brake shoes are trying to collapse them, by the way. It is not needed in a disc brake configuration, and I have seen it often enough bite people when they buy a replacement master cylinder and get the wrong one, both ways.

As a general rule, disc brakes usually require more pedal force to operate than drum brakes, so you may want to consider the power brake assembly for a Kadet as well. Myself, I would try the manual brakes first, before I swapped in all the power brake stuff, because the smaller bore on the 1.1 Master cylinder might make the brake pedal feel acceptable for you, and because I hate the power brake "tower of cr@p" in the Kadett engine bay. If you do convert to power brakes, you will also have to run new brake lines, by the way, because the old ones won't reach the master cylinder in it's new location.

One more thing to consider, while you're shopping for parts, is that the steering arms on the GT are different than the ones on the Kadett too. They have a shorter, angled arm, which mmeans quicker steering and improved steering angles, both of which will improve the "sportiness" of the car quite a bit, without much investment at all. So, if you end up with GT parts as a doner, keep the steering arms too, you will like the difference.

[RallyBob]

Nice recap Stephen, you really hit all the important points.

One other thing to remember is the 1.9 Kadetts have small-pistoned calipers than the GT calipers do.

Bob