When I was at the mini show here in Adelaide, I was drooling over a race car that was on display. This car had a modification that I have not seen on another mini.

It was using a MAZDA tandem brake master cylinder which had a remotely mounted fluid reservoir (which I thought looked WAY cool.)

My question is, would this modification improve anything?

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

i have no idea if it would improve braking or not but maybe it is just alot cheaper to by mazda master cylinders.

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FOR SALE MInidlx, 1293, GR head, RE-13, GR worked Redline Manifold, 45 mm DCOE,pulsar dizzy , "S" Disc's, Mk II "S" box, 3.65 diff. Minator 10X6's On the loose

maybe he is using it cause it is way cool

weird, and why would you bother??

I just bought NEW plastic master cylinders (brake and clutch) for $100 each

I am now wondering if that Mazda master cylinder has a larger bore and piston in it.... therefore reducing the travel required at the brake pedal to move the same amount of fluid.... maybe

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

Was there a brake booster? increasing the master cylinder bore size would increase the amount of foot effort required for similar barking force maybe he was trying to get more feel with a booster fitted. Or maybe he was just trying to get more feel it was a race mini after all and as I understand racers like lots of pedal feel.

I guess another possibility is that he had different type brakes and needed a different bore size to compensate for different wheel cylinder and caliper diplacement (is that the right term? the amount of fluid it takes to activate the brakes on disk brakes)

Maybe

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

Hmmmm..... nope, no booster. Was running 7.5 inch cooper discs.....

A friend of mine bought it that day, but has not yet taken posession of it. I will have to wait and see.

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

Nope, its the opposite. Larger bore master cylinder with standard size brake lines will infact shorten the pedal travel required for the same amount of braking.

Here are the answers to my first question: "..would this modification improve anything? " - answered by the original owner.

1. This modification makes the pedal feel harder, requiring less travel for the same amount of brake pressure.

2. These master cylinders require only a lillte modification to fit the mini.... and cost around $100 BRAND NEW.

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

Sorry SC, you are wrong. Pressure in the brake line will go up if you reduce the MC size, as the same force is applied to a smaller area. But you will get more pedal travel to displace the same amount of fluid.
A bigger MC as here is the opposite- less pedal travel, but more force needed. Simple fluid dynamics.

That's why (for example) the 998 Cooper had a small 5/8" bore MC, to do away with the `pressure intensifier' used previously on the 997 Cooper (3/4" bore MC) and reduce pedal effort.

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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.

Hmmmm.... That point really fu*ks me up then.

The way I calculated it was.... (assuming the brake line is same diameter)..

surface area of piston X length of travel = amount of fluid moved to the caliper.

more fluid = more pressure.

If you are moving a larger piston over the same distance, it will move more fluid, therefore upping the pressure at a greater rate than a small piston would....

How can this be wrong?

What... would the pedal require MORE mechanical advantage or something?

Help.
Confused.

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

Me thinks the good Doc is talking hydrolic pressures within the system while Nath is discussing the distances the pedal will travel, and the Volume of hydrolic fluids moved.

Perhaps if you agreed to compare apples to apples, you may find you ware not that far off agreeing with each other

Yeah.... thats what I was thinking

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[NATHAN] -- Sold everything mini related and am back in big beautiful BMWs

Hey SC850,
Has your mate taken possession of this car yet? I keen on the master cylinder. Won't to investigate what is required to do it as it will give me some room around the manifold.
JC

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But he's thriving and striving and hugging the turns.

In most classes of car racing you must have dual circuit brakes. Historic racing is the exception.

To fit dual circuit brakes you could use a later mini master cylinder or do what this bloke has done. It looks simple and looks like it would work.

Was going to use the mini one but if I can pick one of these up new at a good price i would leen towards the mazda.

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But he's thriving and striving and hugging the turns.