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How I Fitted Rear Discs and MGF Callipers 
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Joined: Tue Jun 17, 2008 9:11 pm
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Post How I Fitted Rear Discs and MGF Callipers
I see that this topic has come up again and, when I did it, I had to do a fair bit of research to figure it out so I have written the whole thing down in the hope that others may find it useful. This is how I did the job and I offer no guarantees or anything else that it will work out for anybody else because every job is different and so are different people's mechanical abilities. If you decide to follow this method please regard it as a framework to adapt to your own needs.

Parts used:
Mini disc brake type hubs
Mini 8.4" solid brake discs
MG Metro drive flanges
Mini disc type CV joints
MGF rear callipers incorporating handbrake mechanism
MGF handbrake cables together with their securing bracket from the lever end and the compensator from the lever.
Mini handbrake lever - later type with single cable and compensator

Method:

Remove rear drum brake set up, hub, cv joints and handbrake cables

Fit disc type cv joints to drive shafts - it is not necessary to replace the shafts because the cv joints are a straight swap.

Fit Mini disc type hubs

Fit Mini brake discs

Fit MG Metro drive flanges - these have a longer nose without which the conversion will not work. They move the flange out to make more room for the calliper and therefore increase the track a little as well.

Fit MGF callipers upside down and on the wrong sides...... They will not fit any other way because the arm to which the handbrake cable attaches fouls the front tie bar. Also, the bolt hole spacing is slightly different between the calliper and the hub so the holes in the calliper will need elongating by a couple of millimetres each. This is easily enough done with a file but be sure to take the same amount off each to keep the calliper central.

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Next, and most importantly, the discs must be centralised in the calliper. As far as I can tell it is usually necessary to machine small amounts off the calliper mounting bracket to achieve this but when I did mine the opposite was the case and I had to shim them with thin stainless washers to get the disc dead centre. A millimetre or so off centre seems to be acceptable and MGF rear brakes are known for wearing unevenly anyway with the inner pads doing most of the work.

The handbrake and cables are next. There are different options here but I went this way because my car was going for it's IVA test and it was necessary to fit a compensator which equalises the balance between the rear wheels (on the rollers at the IVA test station the imbalance on mine was less than 1% )

The single cable type handbrake lever does not mount the same way as the double cable type. The later cars have a bracket on the floor so you will have to make something up for the rear fixing bolt. It's all pretty obvious when you see it.

Bolt the MGF compensator to the lever in place of the Mini one. It has two holes to take the bullets on the end of the MGF cables - fit and secure a clevis pin in each hole.

Attach the handbrake cables to the callipers and route them underneath the sub frame, through the rear bulkhead and into the car. The cables are far too long and need to be shortened considerably. The fixings on the end of the cables can be 'unscrewed' carefully and kept for reuse.

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Mount the front cable securing bracket (which you hopefully remembered to get with the cables) to the centre tunnel and shorten the outer cables only to a suitable length. Reattach the end fittings which you removed earlier by 'screwing' them back on. These are not meant to be removed and replaced but it is possible with a bit of fiddling and a vice is very handy for helping to do this.

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Feed the inner cables round the clevis pins on the compensator and double them back to form a loop which is secured with small cable clamps ( I used two on each side ) making the loops as short as possible and both cables the same length. Cut off the excess inner cable.

That's it. Bleeding the rear is a bit fiddly because the callipers are upside down and trapped air can't escape. I unbolt mine and, with an Eezibleed attached, open the bleed nipples while holding the calliper the right way up. The brake cables will stretch slightly as the loops settle in and may need adjusted. There is not a lot of room for lever movement in the Rossa centre console and one of the two things my car failed IVA on was the lever just touching the top of the slot while being hauled on hard while on the rollers and the loops on the cables stretching as they settled in. This was easily rectified by modifying the console with a large half round file to give more clearance. At no time did the cable clamps slip which was something that I was worried about. I also hid an adjustable brake balance valve ( they're not allowed any more ) in case the balance was upset by the rear discs but it was not needed, the balance was perfect on the rollers.

There are different ways of doing this mod but this is how I did it and I'm very pleased with the result.

Sorry the photos aren't better but I didn't take many of this job :roll: Good luck.

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Sat Aug 08, 2015 10:41 pm
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Joined: Mon Jul 13, 2015 6:32 pm
Posts: 545
GTM: Libra
Post Re: How I Fitted Rear Discs and MGF Callipers
Hi Raymond,

I presume that you have posted this after my plea for information earlier - I'm so glad you did and I'm indebted to you.

Brilliantly set out and has answered all my questions, thank you so much.

While I'm on, I've been reading your previous build diary and if my own Rossa rebuild turns out half as good as yours I'll be a happy man - top job.

Cheers

Jamie


Sat Aug 08, 2015 11:23 pm
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Joined: Mon Jul 13, 2015 6:32 pm
Posts: 545
GTM: Libra
Post Re: How I Fitted Rear Discs and MGF Callipers
Ooops sorry Raymond, I do have one more question.

Do you by how much the Metro drive flanges increase the track?

Thanks, Jamie


Sat Aug 08, 2015 11:26 pm
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Joined: Tue Jun 17, 2008 9:11 pm
Posts: 671
Post Re: How I Fitted Rear Discs and MGF Callipers
Hi Jamie. Glad you find it useful. I'm not certain how much the track is increased by because I didn't measure it but it must be something like 15- 20mm each side. It's not enough to make the wheels stick out anyway if that's what you're wondering. As a matter of interest, when my handbrake was tested on the rollers it locked up the wheels which really surprised the tester who was more used to crappy setups on kit cars :mrgreen:

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Sun Aug 09, 2015 11:39 am
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On the Road

Joined: Mon Jul 13, 2015 6:32 pm
Posts: 545
GTM: Libra
Post Re: How I Fitted Rear Discs and MGF Callipers
Thanks Raymond,

I've ordered some callipers and handbrake cables and hope to emulate your good results. Cheers.


Sun Aug 09, 2015 6:21 pm
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Joined: Mon Jul 06, 2015 8:26 pm
Posts: 124
Location: Chorley, Lancashire
GTM: K3
Post Re: How I Fitted Rear Discs and MGF Callipers
Great post thanks for sharing, good information on the parts and how they can be used.

Looks like a good build :)

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Sun Aug 09, 2015 10:11 pm
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Part built GTM

Joined: Thu Jun 19, 2008 2:02 pm
Posts: 76
Post Re: How I Fitted Rear Discs and MGF Callipers
that is amazing.
very well shared.
thank you.
:-)
i would love to ditch my rear drums and now i know how. . . .


Tue Nov 10, 2015 8:52 pm
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