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PostPosted: November 4, 2017, 9:40 am 
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Joined: June 8, 2010, 8:02 pm
Posts: 477
Location: White Rock, BC, Canada
I would suggest getting the 6:1 ratio. 5:1 really isn't much for a car and pushing hard on the pedal takes some finesse away for performance driving. The spreadsheet should get you close enough for the bias bar to handle the rest. If you find the bias-bar is too far to one end, you should adjust m/c bore size to suit.

Cheers.

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PostPosted: November 4, 2017, 2:44 pm 
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Joined: June 11, 2008, 1:31 pm
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Location: Denver,CO
For starters, my car is a mid-engine locost. It has a VQ30de v6 mid mounted in the rear with the front calipers from a 1997 maxima in the rear. (piston sized 57.2mm) The front brakes are from a 90-93 miata 51mm piston.

I tried to adapt my factory brake pedal master cylinder to my car. When it did drive the results were somewhat disastrous. The fronts would lock under light braking, the rears wouldn't lock at all. The pedal arc is way off and every time I push the brake pedal my knee bends and my foot has to push forward to engage the brake. The maxima brakes had a booster and a 15/16 master cylinder.

I put a proportioning valve on the front brakes and that improved the performance of the brakes but not the ergonomics.

I also added a clutch pedal from an S2000, made it a reverse swing unit and it worked better, but I still had the funky ergonomics of having to push my foot forward rather than pivot my foot.

I found by rising the clutch pedal that fixed the ergonomics, but put the pedal mounts above the scuttle.

My solution is to by a clutch and brake pedal set. I have found they have two ratios 5:1 and 6:1. I'm leaning to the 6:1 but I have no idea what master cylinders to by for the brakes as it is a dual system. I have a fair amount of room to mount these pedals. Do I get equal sizes or stager them. The pedals I am looking at are from southwest speed. http://www.southwestspeed.com/?sec=view_menu&cat=Hubs%20And%20Brakes&sub=Pedals&ssub=Brake%20and%20Clutch%20Pedal%20Combo%20Kits%20With%20M/C&sssub=Reverse%20Swing%20Mount-Long. They have daul masters with a balance bar. The sizes they have available are 3/4", 7/8", & 1.


Thanks

evo

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PostPosted: November 4, 2017, 3:34 pm 
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Joined: April 12, 2012, 11:56 am
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Location: Pemberton, BC
It is a bit of a puzzle, evo, that several have struggled with, including myself. There are spreadsheets, but I think the variables are too many, and in the end, it will need to be tried and tested. I'm guessing that a 6:1 ratio and a stagger with one size smaller to the front might work for you.
I have a floor mounted Willwood pedal, 6:1 ratio, 5/8 front and 7/8 rear. My problem is locking up the rears, with the balance bar all the way to the front. Since I can't change the rotor diameter on either end, I'm thinking of trying a 1" rear M/C. That is the cheapest option, but it will make the pedal even stiffer, and I'm not too sure if it will be too much stagger.
Oh the fun of continuous development. :BH:

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PostPosted: November 4, 2017, 4:08 pm 
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Joined: June 11, 2008, 1:31 pm
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Location: Denver,CO
Thanks.I used Mike Polan’s excel speed sheet and cake up with an ideal master of .713 front and .924 rear. Some of the assumptions were on weight. I estimated 1880 with me in it. (I’m 230). Also I guess the front weight split to be around 40%.

So with these calf’s I would be looking at 3/4 front and 1” rear. Even playing with the numbers this seems to be the closest ballpark.

Evo

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PostPosted: November 11, 2017, 1:28 am 
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Joined: June 11, 2008, 1:31 pm
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Location: Denver,CO
I ended up picking up a set of adjustable wilwood reverse swing pedals on amazon for $130. Normally they are $219 but these were open box. I found I had to completely reduce the steering column mounts to make this setup fit.

I’m also making an adapter to fit an oem clutch master cylinder on the wilwood pedal mount. The master I have is brand new and properly sized for the transmission I’m using.

Evo

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PostPosted: November 14, 2017, 5:58 am 
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Joined: June 11, 2008, 1:31 pm
Posts: 433
Location: Denver,CO
So adapting the oem clutch master is t going to work as the outlet points at the brake masters.

My next question. Is there any real difference in master cylinders besides weight and physical size and price. Looking at the wilwood high volume master cylinders as they are priced well and fit where I’m going to place them. The compact/remote masters are $20 to $30 more than the high volume units.

I’ve read of some sealing issues with the wilwood plastic reservoirs. Is there a real difference between the Southwest aluminum masters and the wilwoods? They have identical measurements to the wilwoods just look to be lacking some finishing.

Evo

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