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Converting a GTM rear drums to 8.4 standaard discs
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Author:  Mini Garage Aalst [ Wed Oct 17, 2012 12:37 pm ]
Post subject:  Converting a GTM rear drums to 8.4 standaard discs
Hello All,

I'm quite new with the GTM's. Got one a few weeks ago for using it on the track.

I've been thinking to modifie the frunt 8.4 disc brakes to 4 pot calipers with vented and grooved discs which should be much better.

But I would like to put the front calipers to the rear.

Has anyone experience with this ? I'm curious if the brake balance would be ok or not and how easy it can be done.

Thanks already
Author:  ibrooks [ Thu Oct 18, 2012 4:50 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
What master cylinder are you running? Mine was running a standard Mini single circuit cylinder with Metro 4-pots up front and Mini 8.4 2-pots on the rear when I got it and it was prone to locking the rears under heavy braking. I then fitted MGF rear calipers working on standard Mini 8.4" solid discs on the rear and found the balance to be near perfect with no bias device fitted. A good stamp on the pedal would lock the fronts and a really heavy stamp would lock all 4 wheels.

I'm in the process of a rebuild and fitting a bias pedal box whilst I'm at it (because I want twin circuits and for some space reasons) and I'm hoping I can get the brake balance just as it was before.

Iain
Author:  the other Tim [ Fri Oct 19, 2012 4:52 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
You will need to change the uprights though :wink:
Author:  Mini Garage Aalst [ Fri Oct 19, 2012 8:36 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
Hello guy's,

What do you mean with "prone" ? The translater gives me something very strange. My native language is Dutch so I don't understand this word
Could you explain it a little ?

Same with up holders


Thanks, David
Author:  Mini Garage Aalst [ Fri Oct 19, 2012 8:38 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
Sorry that should be uprights in stead of holders.
Holders is my translatian of the translation.


Dammm
Author:  Malcolm_Ball [ Sat Oct 20, 2012 12:38 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
Mini Garage Aalst wrote:
Hello guy's,

What do you mean with "prone" ? The translater .........Thanks, David


Hi David - welcome to the english language where one word means two things.

Prone can mean "laying down" :lol: or in this case try "tends to" see if that translates better.
Author:  the other Tim [ Sun Oct 21, 2012 12:27 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
Steering upright, balljoint on the top and bottom, steering arm and caliper or drum brakes bolted onto it. Disc and drum brake versions are different :wink:
Author:  ibrooks [ Wed Oct 24, 2012 2:19 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
Sorry - yes the hub or upright will need to be changed if you are going from drums to discs. I was thinking about what I needed to change on mine which already had the Mini front brakes on the rear when I got it.

You will need to change everything between the top and bottom arms at the rear for a Mini disc brake setup. You will need to modify the hub ever so slightly to fit the MGF brake calipers. You will need to use Metro Turbo drive flanges with standard Mini brake discs. You might need to chang the way the rear hubs are locked in the straight ahead position (the reverse A-arm system used on some Coupes I don't think fits to a disc-braked hub. You will need a brake hose to connect from the Mini pipework to the MGF caliper (the conversion set that you buy to fit the 4-pots to the front has a suitable hose so buy two sets if you are going to do it).

The MGF calipers need to be fitted to the "wrong" sides so bleeding them is interesting - you need to do it with the caliper un-bolted from the hub and turned upwards. Stick a block of wood between the pads so that they don't close up. It's a bit of a pain to do but not something you need to do often so I live with it.

The existing handbrake cables on mine were from a Morris Minor and they fit the MGF calipers OK with the addition of the fitting from the end of the MGF cables (my calipers were from a breaker so they came with part of the cables still attached as they had just cut them). Ideally they need to be shorter so I modified them.

Just moving the Mini front caliper to the rear is a slightly simpler job but the rear braking effort I found to be too much - you could sort this with a bias valve. You would also need to make a different arrangement for a handbrake.

I'm fairly sure I've posted more detail and pictures on here before and i'm not the only one that has done it.

Iain
Author:  Andy [ Wed Oct 31, 2012 10:48 pm ]
Post subject:  Re: Converting a GTM rear drums to 8.4 standaard discs
I did it on mine when I had it (check out Andy's 83 Coupe in the Projects section) I used standard 8.4 discs with Golf Mk5 rear calipers which gave me a handbrake. I used the drum hub and made my own mounting plate which I welded to the hub. Yes you will need to change your locking method but I made this up myself also.
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