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Rear Disc Conversion

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andy

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This is a basic how-to on converting to rear disc brakes using mk3 cav or astra hubs. This is a very simple swap and is very worthwhile since the disc setup brings both better braking and easier maintenance.

 

Now if your thinking of doing this I assume you can remove the beam yourself so im not going through that. The rear brakes will need to be bled afterward and there is a small bit of welding needed on the handbrake adjuster.

 

The easiest way to do it it to get your hands on a complete mk3 cav rear beam complete. This just bolts straight on without any modification leaving you with only the handbrake cable to sort.

 

If however you can't get one of those but can get the disc hubs all is not lost, you can use your mk2 beam.

If for have early NON ABS hubs they will fit straight onto the mk2 beam.

 

If you have ABS hubs it goes as follows

Horrible drums

 

img0369j.jpg

 

 

and off

 

img0371hf.jpg

 

Now when you compare the ABS hub with what you have taken off the problem becomes obvious

 

Old one

img0372cy.jpg

 

New one with stupid massive abs sensor

img0373e.jpg

 

The hole in the beam is too small so to get the hub to fit it has to be opened up to 61mm.

 

img0381e.jpg

 

There are a few ways to do this I used one of these with a carbide tip

 

img0387n.jpg

 

Hole marked up to be widened

 

img0389iv.jpg

 

And done

 

img0391ph.jpg

 

Then it all fits together

 

img0394zg.jpg

 

 

 

Brake line

 

If you have mk3 disc setup ones they fit straight on but if you dont you basically have two options.

 

1- replace the line with some copper or nickel brake line. If you dont have the tools to do this yourself most motor factors will make it up if you give them a length (bending a bit of thick wire into the right shape is a good way to get the right length)

 

2- bend the old drum pipe to reach the caliper. This works OK but IMO a new pipe is the way to go.

 

Ill be making up a new pipe for mine but just to prove that the drum one will fit

 

img0395s.jpg

 

 

 

Handbrake

 

This has to be done no matter what beam your fitting.

You will need to get a pair of mk3 cav disc handbrake cables which fit directly onto either beam. The problem is that mk3 cav cables are longer so you need to loose the slack.

 

The easiest way to do this is to get this little bugger (the adjuster used on both 84-88 mk2s and ALL mk3 cavs)

 

img0386wq.jpg

 

The adjuster is 140mm long overall and by making it shorter you loose the extra slack on the cable. You need to cut a bit out of it (about 25mm) so you end up with it being 115mm long.

Take the width of your grinding disc into account, it needs to end up being 115mm long or you wont get the ends of the cable into it.

 

img0396gt.jpg

 

And weld it back together

 

img0398gv.jpg

 

This is fitted as it would normally be and the mk3 disc brake cable will now fit the car perfectly. Once its all bolted back up and the system is bled your good to go.

You can also use larger Vectra or Saab 9-3 rear disc brakes if you want. Its a cheap 5 stud conversion too. Backplate needs redrilling though..

Edited  by Frisco

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