Hi,
My mini is a bitsa. I have owned it a few months and am working through all it's issues with lots of new parts and refurbing what I can to keep costs down. It's my first mini. Just seeing what the consensus is on what my brakes are. They seem to be consistent with post 1984 disc brakes but they measure 8" diameter, could they be 7.9"? If i bought new discs can I just turn them down to 8"? Maybe that's what has happened in the past.... I have no booster, will these brakes be fairly good? some photos attached, Cheers

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1972 Mk3 Mini 1000, 1150cc supercharged.
https://www.ausmini.com/forums/viewtopic.php?f=3&t=95872

Looks like 8.4s turned down to 7.9"

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks. Do you think 8.4's will fit inside these calipers or must they be turned down?

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1972 Mk3 Mini 1000, 1150cc supercharged.
https://www.ausmini.com/forums/viewtopic.php?f=3&t=95872

They should fit but you will need 12" wheels or bigger. People turned rotors down to 7.9 so they would fit in (some) 10" wheels. Check the caliper mounting lugs for mods too.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Why would turning the disc down help the clearance to 10" wheels, surely it's the caliper that is the constraint.

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Find a job you love and you will never have to go to work !

Thats why drmini has said to check for changes to the caliper mounting lugs. If you machined the disc smaller you'd move the caliper in a little as well.

Can you put the calipers on the hub and check how much clearance you have to the disc?

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Thanks for the input guys, I'm on 12" wheels, the discs measure 8" exactly and the calipers appear to be unmodified.
I'll give you an update and hopefully get some help with a new problem which has arisen....

Today I started assembling the hubs with the GHK1140 bearing kit from minisport. Note that for whatever reason when I disassembled my hubs there were ball bearings in there no tapered rollers. So I knock in the cups and put the hub in the vice to set up the bearings, I have a new disc type CV and new drive flange. Inner bearing on, spacer on, outer bearing on, then disc and drive flange on. I finger tightened the nut and the disc fouled on the ball join before the bearings even took up! What the heck could be going on with it??

I'm at a loss, as my mini has been molested before, I don't know how things are supposed to be. They look to me like 8.4" style discs and calipers. Are there different hubs? Surely the bearings should be all the same. Why would the disc rub on the ball joint like that? Have I done something wrong?

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1972 Mk3 Mini 1000, 1150cc supercharged.
https://www.ausmini.com/forums/viewtopic.php?f=3&t=95872

Some more photos

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1972 Mk3 Mini 1000, 1150cc supercharged.
https://www.ausmini.com/forums/viewtopic.php?f=3&t=95872

Could some kind person please measure their 8.4" style disc for me so I can see if this one is the same?? It's got to be wrong in some way to be causing my problem.
I think, if i buy new discs and pads, and have a new cv and bearings and drive flange, then it HAS to go together, right??

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1972 Mk3 Mini 1000, 1150cc supercharged.
https://www.ausmini.com/forums/viewtopic.php?f=3&t=95872

Put your thinking cap back on Phil...say the rotor was 11", where would the calliper be?

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"Show me the Mini!"

You put the spacer that goes between the bearings in? (at least it does on the S brakes, I haven't done 8.4s ).

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Roads need more corners
A Deluxe(CG13DE), 2 Clubbies(998 and 1275) and 2 Morris 1100Ss

Yep spacer in. Even without it it should still take up on the bearings without the disc fouling on anything. Something funny is going on just need to get To the bottom of it. It's hard having not worked on a mini before this one.

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1972 Mk3 Mini 1000, 1150cc supercharged.
https://www.ausmini.com/forums/viewtopic.php?f=3&t=95872

I think you should compare the old drive flange with the new - if the new flange pushes the rotor further inward then it'll do what you describe. I've no idea why it'd be different though...

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did I tell you that I won a trophy?

Can you get us a photo of the hub assembled with the drive flange and no disc?

Must be a different disc or hub- normally you can drop one of them on a hub with no flange and it still shouldnt touch the ball joint.

For some reason i suspect thats an mg metro disc, or the hub off an 1100 or something whacky.

51mm for the length you have indicated in your photo above.
Assembled, it should be like this (simplified):