bdavis

I am looking to put dual master cylinders on my RallyX EG. Has anyone done this before? I searched but it did not return much.

I would like to keep the brake booster as my wife will drive it as well and if the brakes are as hard to push as the clutch is, she will kick my ***.


Thanks
Burke

slammed_93_hatch

I wont say its impossible, cause nothing is....

But it isnt going to be easy or cheap, and probably not OTS.

Your booster would have to have space to hold two MC.

Every single car ive seen with dual MC does not run a booster.

So if your looking for an adjustable prop just instal the typical tilton pressure one.

cluelessmale

iTrader: (1)

it can be cheap just need to watch ebay, might take a month to get the 3 things cheap.

FerreiraCompetitions

Tandem masters require a new pedal box and never run booster. I dont think that's what you need at all. Specially only on a rally-x car. If you want to better rotate the car in rally-x, try running more rear friction brake pads.

dirty19

iTrader: (1)

A cheaper yet solution!

Jaker

Here's what you need for dual masters in an EG, assuming of course that the RHD is the same configuration as the LHD. These come from Northern Ireland.

Like everyone else mentioned though, you won't be able to run the booster. However, with properly sized master cylinders, you might get away with only a slightly more firm pedal.



from here:

http://www.eg6ek4ep3.com/eg6.php

bdavis

Thanks for the links guys.

I currently run a higher friction pads in the rear. But I do daily the car when I can, but while tapping the brakes on an off ramp and locking the rears is fun, it worries me if/when the wife takes or there is some panic situation.

I plan on using a tilton prop-valve (http://www.summitracing.com/parts/TIL-90-1003/) in conjunction with dual masters to give me all the adjustability in the world.

Right now the engine is out, so i figure if I am going to do this, now is the time to route all of the lines, etc.

I have access to fab what I need, I think the only thing holding me back will be space constraints on booster. But as someone had mentioned, with the properly sized master's maybe the pedal wont be that bad.


Thanks for the input everyone.

Burke

FerreiraCompetitions

Dont take this the wrong way, but very respectfully I dont think you know what you want or know what a pedal box can do. IF you have a pedal box you will NEVER need a prop valve, because the pedal box IS the best way to adjust bias.

Your car is not at the level where a pedal box is needed, therefore, if you route new lines, drop the OE prop valve and install an adjustible one inside the car you will get the desired effect without all the fussing and issues pedal boxes bring. Setting a balance bar and pedal geometry on a pedal box is more difficult than people think. Once the M/C sizes are chosen and static pressure bias set, then the rod length stager needs to be setup so that the pedal doesnt go "over center" and to properly set the engagement timing of the fronts and rears, then there's the bias migration that occurs typically @50hz, etc, etc... so I dont think what you're looking for takes that much time and effort, specially when you can get a prop valve for $50 vs a decent pedal box for $500+.

Here's a taste of what you're in for if you get a tandem master system
http://www.performancefriction.com/p...20401_Bias.pdf

Stinkycheezmonky

I was thinking the same thing, but you said it nicer.

bsclywilly

This is a dual MC setup that I designed and built for my TT/daily EG. It is very beneficial to have the ability to adjust brake bias and eliminating the booster provides a much firmer feel at the pedal which can give the driver more confidence.

For rallycross and autocross, or for tracks that don't require alot of threshold braking but more partial braking, I would recommend that a prop valve (adjustable or not) be installed in addition to your dual MC or stock setup. The prop valve will vary the bias depending on the amount of braking force applied so that on lower traction surfaces the bias is balanced a bit rearwards but as braking force increases (higher traction) the bias become more forwards when you need it. Helps alot with trail braking. If you're using only a bias bar, then you have a fixed bias which will be optimal for a smaller range of decelleration.

This pic just shows the top half of the MC mount



I can provide you a similar setup if you're interested.

slammed_93_hatch

bsclywilly- It is hard to tell from the pictures, but Does your dual MC have an adjustable balance bar?

bsclywilly

Yes. You can see the threaded end and jam nut on the side of the clevis. The MC's and bias bar are Tilton hardware. The lines from the MCs go to a tee fitting for the front and rear circuits using the stock hard lines. And the tie-rod on the bias bar housing goes to the stock brake pedal clevis. Under pressure, the pivot that the bias bar housing is on is 1:1 which should minimize any friction from that joint.

When I roll in to tech inspection it's always nice to hear that it's the best brake pedal the scrutineer has ever felt.

RR98ITR

Cute setup. Really tight clearance to the shock tower, necessitating the tight packaging and the presumed really limited range of adjustment. And it also clears the belt driven intake manifold too. Nice.

Scott, who would remind some that Prop Valves and Bias Bars have subtle and useful differences...Bias Bars take you in a straight line from zero to wherever...Prop valves can take you to that wherever from a higher initial rear bias slope...could be useful...

bsclywilly

It's a standard 2.5" c-c bias bar. It only takes about 5 turns to go from a wet setup to a dry. I've been to a couple autocrosses and I think I could use even more rear bias than that, hence why I think a prop valve is still necessary. The disadvantage with a prop valve on road courses is that you increase the pedal force required for a given decel. So either you push harder, or you increase your pedal travel.

There is also some advantage to set it up slightly rearward biased even under peak decel rates. Rotates the car better on turn in but sacrifices max straight line braking capability. I'm seeing max 1.2g under braking with street tires.

bdavis

This why I will be using a prop valve as well.


Also if I only went with a prop valve, then I would loose all brakes if I busted a line on one wheel. I do some stupid stuff in the car where this could very possibly happen I am doing this all in hopes of the car making its way to a stage rally someday. But for now running around in dirt, horse tracks, occasional pavement, and my yard is all I can afford...

slammed_93_hatch

your talking about something like pictured in the summit link right?

how is something like that going to get you more rear bias.

my understanding is the "max pressure" is all the open, like not have a prop valve. And it only reduces pressure from there.

bsclywilly

I should clarify.
I would add the prop valve to the rear line and then turn the bias bar to a very rear bias setting (or increase rear caliper piston/reduce rear MC piston area). So the car is rear biased under low decel and more front biased under hard braking (since the prop valvve restricts the pressure to the rear as you increase pedal force).

FerreiraCompetitions

In theory that could work, but if in reality it did, then all pro-race teams would do it, meanwhile they stick with the correctly sized tandem masters, and only use the balance bar to adjust the bias to correct for race conditions. Fuel levels, aero changes, etc. Never more than 2 or 3 percent because then it screws with the pedal and rod geometry and you get umpredictable behaviours.

Stinkycheezmonky

Yeah, prop valves (at least to my understanding) can only increase front bias/decrease rear bias.