LocostUSA.com

Hi guys,

I'm thinking of designing the pedal box. I don't like the bias rod design. I'm thinking of using two clutch master cylinders from mitsubishi mentero as a brake master cyinders. The two master cylinders has a solid connection to the pedal, rather than bias rod. A proportional valve is attached in the rear brake line to control the pressure to the rear brake slave cylinders so that you can control the front-rear brake froce distribution.

Will such a plan work? Did anyone build something similar to this? Can I use clutch master cylinder for brakes? I have seen a lot of racing master cylinders that were designed for both brakes and clutches.

Yes, it could work if the masters move enough fluid and the reservoir has enough capacity with well worn pads (it doesn't look like it from the pic).

I don't know anyone who has done this; probably because there is no benefit over a standard dual circuit brake master that probably costs less than two clutch masters and rebuild kits are available.

While right now it may be easy to find cheap montero clutch masters, don't expect that to be the case in 10 years. Standard, common parts, universal racing or oem for something popular are the safest bet.

Usually the best brake balance curve comes from a balance bar and a prop valve but a standard single master system with adjustable prop works fine and is cheaper long term.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
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360LA 442E: 134.5x46x15
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Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

It might work, but using the same size cylinder for both the front and rear brakes is probably a problem. Unless the piston size on the front and rear calipers in the same one cylinder is going to meet resistance first, then you linkage will have to flex. The rear cylinders are probably going to be smaller so that will meet resistance first, I am not sure a proportioning valve well help as you going to have to keep pressing harder to flex your linkage to get good pressure to the front calipers.

Looks like a lot of effort for little or no return.

Graham

The front and rear cylinders don't move the same amount. If there isn't some sort of bearing in the bar, something will eventually fail.

_________________
-Andrew
Build Log
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I do not see any advantage in using two M/Cs if you have them tied together mechanically. As already stated, the two need a bias bar to function properly. You seem to not want that for some reason.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

I'm not aware of any reason that a clutch master cylinder couldn't be used on a brake circuit... However, the design you are proposing not only offers no advantages over either type (bias bar or tandem master cylinder) of conventional system, it's actively dangerous.

It would seem that what you don't like about the bias rod design is probably what makes dual master cylinders work at all in the first place. If you were successful in locking the movement of the two pistons together, the each will then be putting an equal volume of fluid through each circuit regardless of the resulting respective line pressures. Your smaller volume rear circuit will pressurize much faster than your front circuit, and you probably won't even have the pedal travel to bring the front circuit up to pressure. A proportioning valve can only reduce pressure, not volume, so it would not meaningfully help in this case. While having the same size calipers at all 4 corners might work, or diagonally connected circuits, any minor imperfections and you'll lose the desired pressure ratio. There is a very good reason that tandem master cylinders all have the added the internal complexity of having each circuit independently operated by two separate pistons. It's the only reason they work as safely and effectively as they do. If you don't like the balance bar design, just get an appropriately sized tandem master cylinder and call it a day.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

I was thinking about doing the same thing, but it seems like it is not a good idea.
Any input of what should I use for a braking system(street use)? I'm thinking about making my own pedal box(Westfield style).
Which master cylinder should I use? I guess, it should be a tandem then. 7/8" bore(Wilwood recommendation) is a good size?
Also, they recommend a 3/4" bore master clutch cylinder.

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Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

I have a 3/4 and a 7/8 iirc - both wilwood on a wilwood mount. One for fronts and the other for rears. You will want some sort of bias bar or a valve on the rear circuit for adjustment.

Look at Facebook marketplace - you can easily find a lightweight pedalbox.

Most likely I will make a biased version, but I was hoping to avoid the complications.
I'm not looking to spend hundreds of dollars on a baking system. It has to be the Locost way.
I'm thinking about getting some Ali cylinders, and building the rest myself.

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

Why not use a dual circuit master? That is what they were made for and they do it very well.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

I would go with that, it is much easier, but which one?
Maybe a VW Beetle(classic) that it's made for disc/disc?
Some others are saying that it may not work, then I will still be going the two single cylinder way.
I agree, that with the two cylinder way I have more flexibility, but it is more complicated and more costly.
The tandem one has only one size bore, that won't be an issue?

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

To be honest, I don't know. My donor car provided the entire drivetrain including hubs, brakes, wheels etc. I used that master and proportioning valve, without the power brake servo. I had no problems at all with braking. Somewhere on this site there is a great brake spreadsheet. It may provide some assistance.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

I can't find your build topic Tibimaki.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12