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MG Midget and Sprite Technical - Triple Master Cylinder in Stock Bracket

So i've looked through the archives and found some good information on fitting all 3 Wilwood/tilton master cylinders in the stock housing. I'll get pictures up of my build here in the next few weeks. But wanted to help out and get some detailed documentation.

My build is based on the Peter May setup, which doesn't widen the stock housing. (So it all fits without moving the wiper motor or cutting the wing)

It did, however, require the master cylinder mounting brackets to be machined down a little bit for the width.

If anyone is interested in specific details; or the parts required to do this. Let me know. I am making enough parts to build 2 in case someone was looking to purchase a setup.

Thanks Guys!

Josh Meacham
Mg midget
Rx7 Rotary Engine
Mazda Rear End
4-Link
4 wheel mazda disc brakes
and soon...Triple Master Cylinders.

Jm Meacham

I'm interested.
J Bubela

I want to check out your sexy fine rear end

Prop
Prop and the

Preview of Mounting Plate

I will hopefully get time to machine the master cylinder flanges down this week. Stock width on each master flange is 1.7in, I will need to narrow them to 1.5in.


Jm Meacham

This is certainly a silly question but as I don't understand, I will ask it anyway.
One for clutch, one for brakes, but what is the 3rd master cylinder for?
GuyW

Guy,
probably Josh will say I'm totally wrong but I'd guess there are two master cylinders for brakes, front and rear, to give more control and adjustment over the brakes.

Makes me wonder if for the auotosolo(?) type racing they could have a separate cylinder for handbrake but not as big as here - I might be wrong about that too, both ideas are just something in the back of my mind
N Atkins

I think you are right about a hydraulic handbrake, but that has its own reservoir built in by the handbrake lever.

But a third cylinder does make sense for split circuit brakes. That must be it then ! Thanks.
GuyW

Yes, the third master cylinder is for separate brake cylinders front and rear. The linkage to the brake pedal will allow the braking effort to be biased front to rear. This is helpful when adding rear disc brakes, upgrading front brakes, or when having the ability to change braking bias in a racing application is needed.

The main hope of using the stock bracket, is that one wouldn't need to chop up the sheet metal on a more valuable car to do this. (Mine doesn't fit in that category, but this option seems to be the cleanest thus far)
Jm Meacham

Here's a picture of one I made last year, fits a treat




Martyn Wilks

And fitted



Martyn Wilks

Yes. Admittedly been reading through your posts from last year and copying what you've done. Great set-up and ultimately after looking over your thread, the reason why I abandoned a pre-fabricated wilwood pedal set. I'll once I've got it built I'll be sure to upload dimensioned drawings of the parts. I know there are others out there offering similar versions....but some of us are simply DIY types (and smaller pocketbooks).
Jm Meacham

Cylinder Flange is narrowed from 1.7in to 1.5in. This was done on a mill, but could be done by hand with a file if needed. This gives enough room between the brake masters for the pivot bar system to work, and still fit the cylinders within the stock bracket width (5.1 in)


Jm Meacham

I used the new plate I made as a holding bracket to machine the cylinders to width. Again, i could have installed the cylinder in the top hole location, and then filed it down to fit the width i needed.


Jm Meacham

I'll have to trim down the balance bar threads, and I did have to narrow up the balance bar tube (1in Tubing from 1.5in long to 1in long), but otherwise this is just a tilton off the shelf setup. I'm getting ready to cut out the new linkage tabs that will weld to the pedal assembly and then its just getting ready to fit into the stock housing and bolt into the car.


Jm Meacham

Will the cut down 1" tube allow for enough adjustment? I'm in the process of making my own version with the clutch m/c mounted outside the standard box but the pedals are still inside so no mods needs.
Have you got the dimensions of your mounting plate? I.e. How are apart the m/c are mounted etc?
Thanks
Jon


Jon White

I also incorporated a couple of pressure sensors so I can adjust the front to rear balance


Martyn Wilks

Martyn
What do they do? Does it just allow you to monitor the actual % pressure? I assume you have a digital readout somewhere?
Jon White

The mounting plate is 5.1in wide by 3in tall. The spacing is such that the two brake masters are 2in apart and the clutch and the next brake master is 1.5in apart. Spaced at 2in apart, there seems to be plenty of room for the bias bar to move where it needs to. Roll cage tubing on my car made it such that i didn't have room to mount the clutch offset like you're doing. Though I've seen it done that way some and it looks like it ought to work as well.

I like the idea of pressure monitoring. Something I will think about.

Tilton lists the distance from "Off Center" the bias bar can be, and what percentage braking that would equate to. I was going to add a counter dial to my adjustment knob and determine braking bias based on how many turns +/- from center I was at.
Jm Meacham

Just a couple notes

When hooking up the masters use stainless steel braid lines with AN fittings...the angle to try and hook up hard rigid brqkes lines is near imposiable to line up

the bias its 90/10 on the spridgets

The easiast to adjust... find a flat non trafficed road ... run the car up to speed, then slam on the brakes and just keep adjusting rince and repeat until you get the braking you want.

The pressure idea is good, but there is so many factors and slope built into the car... its going to be more of a suggestion then a fact

P.
hreadlist

The pressure sensors are linked to a SPA Design Brake Bias gauge which has a front and rear display.

My cars brake lines are entirely stainless steel with AN fitting except the line across the rear axle, which uses the original tee fitting with a suitable AN adapter.

All the lines run inside the car including the fuel line, which I used Goodridge 811 hose and fittings.

Martyn Wilks

What size cylinders and part numbers did you use?
J Bubela

Front and rear brakes 0.625" clutch I think is 0.750
Martyn Wilks

"the bias its 90/10 on the spridgets"
Not so. The piston area ratio is 86:14 (2" front, 3/4" rear), but this takes no account of the self-servo action of drum brakes' leading shoe. Once this is applied, the actual braking effort split is close to 2:1. The influence of self servo is immediately evident when converting to disc brakes on the rear, where area ratios are in the order of 2:1 to get front:rear balance.
Paul Walbran

Sorry paul,

We have covered this several times over the past decade the 90/10 balance is a published spec.

The balance for most cars is between

80/85 to 20/15

The midget is 90/10... i think its lusted in haynes

Prop
hreadlist

Prop when modifying the car, factory specs go out the window. Lots of variables will affect brake setup - tyre grip, position of C of G, spring rates, weight distribution etc etc.
The ideal split is that under max braking the fronts just lock up before the rears. Almost impossible to calculate a fixed ratio - it will even vary by weight of different drivers of course, hence why people fit adjustable bias valves. Not forgetting that one wants to wind off rear braking in wet conditions.
davidsmith

Hey david

Thats why i suggested ... NOT using pressure guages.

AND JUST find a section of straight abandon road and race it and slam on the brakes then adjust the cars balance untill it brakes the way you like for good braking

Its really simple just an allen screw in the porportioning valve and then a twist

In you can even buyba device from tilton that screws onto the proportion valve and you can adjust rhe bias from inside the cockpit

Prop
hreadlist

Sorry Prop, not so. At all. Repeating something wrong many times doesn't make it right. The Midget piston area ratio is 86:14, add in the drum self-servo and it pulls well back from there.
Front wheel drive cars will certainly be biased more to the front than RWD.
But yes, when modifying then adjustable bias is the best was to achieve balance. Personally I like the back to lock just before the front, but that's my rally bias coming through :-)
Paul Walbran

Any updates?
Jon White

It's a tight fit, but it fits.

I'll get a copy of my excel spreadsheet loaded once i can figure out how to load other file types.


MY CAR is NOT stock. So choosing master cylinder size is going to have to be a bit different for each application. However, you can calculate this based on your vehicle weight, wheel size, center of gravity, caliper size, rotor size, ect. It's not as simple as "choose pressures" but it's not impossible either. You can find many brake bias calculators online:

Here is my setup:
Mazda Rx7 Front Rotor
Mazda Rx7 Rear Rotor (axle)
Mazda Rx7 Front Caliper
Mazda Miata Rear Caliper

.625 Clutch Master
.75 Rear Master
.625 Front Master

The pedal setup is a 7.11 pedal ratio, giving me a require pedal force of 60lbs, and a pedal travel of 3.66in. This "feels" right to me, but we'll see once the car is rolling and I can take some actual measurements.

This allows me to adjust from 70/30 Front Biased to 90/10 Front Biased by adjusting the knob 3/8in off center each direction. My initial target will be to adjust for an 80/20 and then adjust from there with road testing.


Jm Meacham

Pedal Assembly Linkage


Jm Meacham

Bias Adjustment could be done in the engine compartment, or via a remote knob in the cabin.



Jm Meacham

Excellent, what are of bias bar did you use and did you cut the tube down.Thanks
Jon White

Would a proportioning valve such as http://www.speedwaymotors.com/Compact-Adjustable-Proportioning-Valve,1979.html work instead of the balance bar? The two piston rods could be fixed to the foot petal lever and the valve in the drivers compartment do the adjusting on the rear brake line? Just a thought. Opinions from the members.
J Bubela

Well done jim...nice job

The only issue i see because yours is an american car it the gap around the adjusting perportioning bar

Beause we in the usa sit directly behind the exhauste. Manifold the heat from it will get sucked into thst hole and down onnto your feet... nice in the winter ... freaking hell in summer..on my tilton set up i used a bread pan and an old door seal and made cover to keep the heat out

With tiltoni filled out an on line form they had with my specs and they sent back the next day there recommendation for master cly... and they nailed it spot on...free be !!!

Also but some time into adjusting your clutch properly ...i found that can get a little tricky and a bolt thur the floor behind the peddle was a good cure for over throwing the clutch when depressing it

Prop

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This thread was discussed between 17/03/2017 and 06/04/2017

MG Midget and Sprite Technical index

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