29 replies to this topic

[Spider]

Crazy what you end up finding. Good thing I decided to check.

 

So what do you think is best in order to get them right?

 

Was looking at the minispares brake id chart but obviously there is nothing there that suites  a black tandem mc running 7.5 discs  with a regulator.

 

The only closest match I see on that chart is the black tandem mc used on 1275GT Diagonal split with 8.4" discs and that used 1/2" rear wheel cylinders with no regulator.

 

for the life of me I cant figure out why people don't do things properly the first time. Its not really that hard is it.

 

 

As Graeme pointed out, the discs you have are 8.4", not that that changes much on the rear brakes.

 

The Mini Spares chart seems to only cover cars made for the UK market and doesn't cover all possibilities.

 

We had a Mini made here, it was called a 1275LS, it was similar to the UK 1275GT, These had a Green Tag Master Cylinder, which was the same as the Black Tag, only the threads for the fittings were M10 x 1.0, instead of 3/8" UNF.  These had 8.4" discs up front, 5/8" Rear Wheel Cylinders and one of those dreadful FAM7821 valves. These were configured front / rear split like yours.

 

Our 1275 Californian Mokes also had a similar set up, only on those, they very soon dropped the FAM7821 Valve in favour of the 13H7757 Inertia Valve.

 

I feel it's a better brake set up if you can use the largest rear wheel cylinders you can, that avoid lock up and for your set up, as I suggested above, the 5/8" Cylinders are what I'd fit, along with a Valve of one type (but not the FAM7821 !).

 

Typically, the 1/2" Cylinders were only used with a Diagonal Split System as it's not easily possible to fit a Regulating Valve of any sort for the Rear Brakes in such a set up, however, these also give next to no rear brakes.

If you were to change to a Yellow Tag Master Cylinder, as these have stepped bores, then you could go to 11/16" Rear Wheel Cylinders.
 

[Ethel]

I think you'll find you have 8.4" discs

 

"Hiding in plain sight" 

 

The piston area on 7.5, 8.4 & 4 pot calipers is  much closer than the rear cylinders, so it shouldn't matter as much. 

[mvahora]

 

Crazy what you end up finding. Good thing I decided to check.

 

So what do you think is best in order to get them right?

 

Was looking at the minispares brake id chart but obviously there is nothing there that suites  a black tandem mc running 7.5 discs  with a regulator.

 

The only closest match I see on that chart is the black tandem mc used on 1275GT Diagonal split with 8.4" discs and that used 1/2" rear wheel cylinders with no regulator.

 

for the life of me I cant figure out why people don't do things properly the first time. Its not really that hard is it.

 

 

As Graeme pointed out, the discs you have are 8.4", not that that changes much on the rear brakes.

 

The Mini Spares chart seems to only cover cars made for the UK market and doesn't cover all possibilities.

 

We had a Mini made here, it was called a 1275LS, it was similar to the UK 1275GT, These had a Green Tag Master Cylinder, which was the same as the Black Tag, only the threads for the fittings were M10 x 1.0, instead of 3/8" UNF.  These had 8.4" discs up front, 5/8" Rear Wheel Cylinders and one of those dreadful FAM7821 valves. These were configured front / rear split like yours.

 

Our 1275 Californian Mokes also had a similar set up, only on those, they very soon dropped the FAM7821 Valve in favour of the 13H7757 Inertia Valve.

 

I feel it's a better brake set up if you can use the largest rear wheel cylinders you can, that avoid lock up and for your set up, as I suggested above, the 5/8" Cylinders are what I'd fit, along with a Valve of one type (but not the FAM7821 !).

 

Typically, the 1/2" Cylinders were only used with a Diagonal Split System as it's not easily possible to fit a Regulating Valve of any sort for the Rear Brakes in such a set up, however, these also give next to no rear brakes.

If you were to change to a Yellow Tag Master Cylinder, as these have stepped bores, then you could go to 11/16" Rear Wheel Cylinders.
 

 

 

Awesome, thanks a lot. 

 

how much of an improvement would there be between yellow tag MC with 11/16 cylinders VS using the existing setup with 5/8 cylinders?

 

Worth the cost to change?

Edited by mvahora, 23 July 2023 - 02:21 AM.

[Spider]

Awesome, thanks a lot. 

 

how much of an improvement would there be between yellow tag MC with 11/16 cylinders VS using the existing setup with 5/8 cylinders?

 

Worth the cost to change?

 

If your Black Tag Master Cylinder is in good order, run with that and 5/8" Cylinders.

 

There's a small reduction in pedal effort, that's all. It won't otherwise improve braking performance.
 

[bpirie1000]

pics

Think i would be more concerned with the bolt that holds the caliper together appearing to have been cut down slightly (for your wheels i suspect)

[mvahora]

 

pics

Think i would be more concerned with the bolt that holds the caliper together appearing to have been cut down slightly (for your wheels i suspect)

 

 

I didn't even notice that until you pointed it out. Checked and both sides are like that. The previous owner had 12x6 non deep dish minilights on the car before deepdish 13x7s were put on. Looking at it more in detail, it seems the body of the caliper has also been grinded/reshaped eg. areas around the bolts and also on top of the AP logo. Any idea why this may have been done? Don't tell me I have to buy new calipers lol. 

 

It was driven with the 13x7 for a long time and there were no issues. The mini was then parked up in storage and unused for years. Now I've gotten my hands on it so am trying to do a proper restoration. Finding more issue the more I open it up    

Edited by mvahora, 23 July 2023 - 09:38 AM.

[bpirie1000]

I would certainly say it was due to an old set of 10" rims.

I would see if the thickness can be established. AP obviously tested the calipers and made the wall thickness for a reason. Brakes are something not to mess about to much with..

Did you get the rear cylinders sorted out..

[mvahora]

I would certainly say it was due to an old set of 10" rims.

I would see if the thickness can be established. AP obviously tested the calipers and made the wall thickness for a reason. Brakes are something not to mess about to much with..

Did you get the rear cylinders sorted out..

 

 

 

Awesome, thanks a lot. 

 

how much of an improvement would there be between yellow tag MC with 11/16 cylinders VS using the existing setup with 5/8 cylinders?

 

Worth the cost to change?

 

If your Black Tag Master Cylinder is in good order, run with that and 5/8" Cylinders.

 

There's a small reduction in pedal effort, that's all. It won't otherwise improve braking performance.
 

 

 

 

Just measured my discs and they're only 200mm diameter (7.9").  Looks like someone in the past has grinded down the discs and also grinded down the caliper to fit 10" wheels. Its all making sense. 

 

Looks like I'm going to have to buy new discs and calipers. Oh well, just another day in the life of a mini owner. 

 

What are my options for new discs and calipers, what's recommended?

 

@bpirie1000 will prob keep the black tag MC and use the 5/8 rw cylinders as spider suggested.

Edited by mvahora, 24 July 2023 - 08:50 AM.

[Ethel]

I know turning down discs to 7.9 is a thing, but I'd be wondering if anything has also been done to move the caliper mountings on the swivel hubs. Probably worth investigating for consideration in your plans.

[mvahora]

I know turning down discs to 7.9 is a thing, but I'd be wondering if anything has also been done to move the caliper mountings on the swivel hubs. Probably worth investigating for consideration in your plans.

 

have uploaded some more pics at the link below. let me know if you guys spot anything

Edited by mvahora, 04 November 2024 - 11:58 AM.

[bpirie1000]

Everything else looks alright. The caliper has been fairly modified and i suggestchanGing them is the best option if you intend to remain running the 13" wheel and tyre set.

10" rims are in my opinion the best option for a mini. The 13" rims pull you from pot hole to pot hole.

Consider things now and future proof your car.

Eitherway well done for making the decision to post on here for the wealth of knowledge.

[mvahora]

Everything else looks alright. The caliper has been fairly modified and i suggestchanGing them is the best option if you intend to remain running the 13" wheel and tyre set.

10" rims are in my opinion the best option for a mini. The 13" rims pull you from pot hole to pot hole.

Consider things now and future proof your car.

Eitherway well done for making the decision to post on here for the wealth of knowledge.

 

I just love the look of the 13x7s on the sportpack flares so cant get away from them.. Maybe in the future Ill have to try find another mini and then keep them both 

 

Who supplies the best calipers? 8.4s I'm assuming? vented/grooved or plain discs? 2 pot or 4 pot?

 

Would it be worth installing tapered bearings into the uprights?

Edited by mvahora, 25 July 2023 - 10:26 AM.

[mvahora]

so after reading on the forums decided on the MSSK014 (8.4" BRAKE DISC & MINTEX PAD KIT) and the standard 8.4 2 pot calipers all from minispares

[mvahora]

 

Awesome, thanks a lot. 

 

how much of an improvement would there be between yellow tag MC with 11/16 cylinders VS using the existing setup with 5/8 cylinders?

 

Worth the cost to change?

 

If your Black Tag Master Cylinder is in good order, run with that and 5/8" Cylinders.

 

There's a small reduction in pedal effort, that's all. It won't otherwise improve braking performance.
 

 

 

Need clarification on the rear pressure reducing valve and if I need to change the valve or the spring inside it.

 

The one that is fitted in my 77 mini is the 21A2031 which was designed to work with 3/4" rear wheel cylinders when drums were all around the car.  

 

Since I now have 8.4 discs on the front and am going to use the 5/8 rear wheel cylinders; will I need to change pressure reducing valve to the 21A1774 which was suited to models that had 5/8" bore rear wheel cylinders?

 

I can change the spring if this is necessary because I don't want to waste money on an entire new pressure reducing valve.

[Spider]

Need clarification on the rear pressure reducing valve and if I need to change the valve or the spring inside it.

 

The one that is fitted in my 77 mini is the 21A2031 which was designed to work with 3/4" rear wheel cylinders when drums were all around the car.  

 

Since I now have 8.4 discs on the front and am going to use the 5/8 rear wheel cylinders; will I need to change pressure reducing valve to the 21A1774 which was suited to models that had 5/8" bore rear wheel cylinders?

 

I can change the spring if this is necessary because I don't want to waste money on an entire new pressure reducing valve.

 

 

Ideally yes, you would want to change the spring. I'm sorry, I am on the road for the next month and so I don't have all my data to hand, but off hand the cars with discs up front had a 450 PSI shut off pressure and yours, if it's from a car that had drums, would have been around 300 or 320 PSI, so that one will work and not lock the rears, but won't give as effective rear brakes as it could.