00MugenS2

As far as I can tell, no one makes a booster delete kit for the miata to run manual brakes. And I haven't been able to find any information about anyone doing a booster delete.

Any suggestion on where to find any information about doing this? I've already bought what I need to build the MC mounting plate but I think I am over thinking the ratio adjustments and MC bore size to get the pedal travel and firmness where it needs to be.

mcfandango

iTrader: (1)

There is no kit. It is dirt simple to build a mounting plate. I did it a few years ago on the XP.

I pressed the 4 studs out of the booster and used those on a piece of 12 (ish) gauge steel and a couple bolts to hold the master cylinder in place. You'll have to fab a new push rod using the parts from booster. I don't have a picture of that but all I did was get a long bolt the right threads for the clevis, cut it to the right length, drilled and tapped the center for the end that of the factory rod that pushes in the master.

Works fine, just a little different brake feel. You can drill the pedal and move the clevis up to increase the pedal ratio. ~5:1 is the limit though, factory is 4:1. Anything higher than that and you'd need to move the master up some.

00MugenS2

What pedal ratio r u running?

I have a 1/2 plate of aluminum that I plan on using moving the MC up to run about 6:1. I've installed the Massive kit on e30 BMWs and the plate moves the MC to the very top of the hole in the FW.

Leafy

iTrader: (1)

Cool. How is the firewall flex with that setup?

mcfandango

iTrader: (1)

1/2" Aluminum is overkill. There is no reason to run that large of chunk of metal. You'll not be able to use the studs in the booster. Build a brace from the shock tower to the end of the master or firewall if you are worried about flex. A chuck of 12 gauge steel is still thicker than the firewall and all that is needed. Usually can find a piece dang near the right size in the drop/scrap piles at the local metal yard.

Right now the pedal ratio is 5:1. I grabbed the wrong drill bit when I drilled that hole. Ended up using the one I was reaming the edges of the hole with instead of the correct size. So there is too much play that makes the pedal feel off. I also added a 6:1 hole but haven't pulled everything apart to move the holes to move the master cylinder up. I'm going to move it back to 4:1 for the time being until I can get a new pedal or fab a bushing to fix my over drilling.

FWIW: Most Miata based Locost guys end up using the 5:1 pedals (mainly as the 6:1 are harder to fit) and size the masters to match the factory calipers.

Firewall flex is pretty minor. I don't have a dial gauge but I've seam welded everything I could on the firewall. Both sides. I also welded the firewall to the front 1" cage tubes. They run from where the old dash bar was to the towers. I did setup my calipers to act as a dial gauge. I didn't see any movement when I was mashing the pedals.

Leafy

iTrader: (1)

I know with the stock setup when just bleeding the brakes with no assist from the booster I get a visible amount of flex. Hasnt been a big concern because its not visible when using the booster. But seems like it could be an issue unassisted. I want to eventually go unassisted and run separate masters, but not yet.

mcfandango

iTrader: (1)

Welding the seams helped a bunch. I used to be able to push down on the wiper/cowl area. There was a very audible creak and you could feel the area move downward. The noise and movement stopped after welding and adding the front tubes. I also added a 1" tube from the dash bar to the floor that tied into the "door bar". Basically replicate part of the Frog Arms on the inside of the chassis.

Alta_Racer

iTrader: (4)

Link

https://www.miataturbo.net/suspensio...46/#post779808

This is a great idea too, I may do this.

http://www.aggressiveautoculture.com/wp/?p=984

z31maniac

What would be the reason to do this if you aren't going with dual masters?

mcfandango

iTrader: (1)

Booster is roughly 10 lbs up relatively high in the chassis on what tends to be the heaviest corner of the car, especially on turbo'd cars.

I figure at under 1800 lbs for an autox car, the need for assisted brakes doesn't exist. Plus braking is usually not a priority for autox vehicles. But those are my reasons.

For others, it is probably similar to power vs manual steering type thing. The pedal feeling definitely changes after pulling the booster.

k24madness

iTrader: (6)

I would love manual brakes. I am use to standing on the whoa pedal of previous race cars and would like to get back to the same on the Miata. I guess with enough seat time I would get use to things as is but manual brakes are a better choice for a track car IMHO.

Radioheavy

I did this mod several months ago on my '99 NB. My setup is a replica of Chase Bays system. I purchased a Manual conversion plate from Rywire and had it powdercoated black. Added a Wilwood 7/8 MC & proportioning valve and plumbed all the hard lines into the cabin using bulkhead fittings. I had DOT certified SS flex lines made for the cabin and t'd everything off the hard line coming in from the MC. I installed my proportioning valve right below the steering wheel for on the fly adjustments. The location does not interfere with my knees.
Pedal feel is stiffer but, very manageable. I've already had a couple of instances on the street that required hard braking (idiots!) and the brakes responded perfectly.
This was pretty easy to set up. I recommend using a high quality flaring tool like Mastercool. I used Cupro (copper/nickel) for the hand formed hard lines. It looks good, easy to bend & flare and meets SAE & ASTM standards.

FatKao

I should be sketched out by a car in the race prep section having single circuit brakes, right?

00MugenS2

I was thinking the same thing. That's why I wanted to use the stock MC.

I got the plate made today, just need to pull the pedal drill the new clevis location. Ill take a few pics tonight.

Leafy

iTrader: (1)

Have you ever driven a stock MC car where you lost the rear circuit? I havent in a miata, but I have in plenty other pieces of crap and mid 2000's GM trucks. Might as well be single circuit, pedal goes to the floor no brakes at all even though one of the circuits is intact. It never seems to work in practice like its supposed to work in theory, maybe if the reservoirs were separate it would work.

Savington

iTrader: (31)

Yep. I've had the, erm, privilege? of losing a single corner of brakes in a Miata a couple of times now. One RF, one LR. All the braking ability goes away as soon as you lose the first line.

Alta_Racer

iTrader: (4)

Exactly why I am looking at dual masters. Even then the brakes will not be great with the loss of a circuit, but it will be at least better. Add the bias adjustment as a bonus and I see a win.

Leafy

iTrader: (1)

You dont get very much there either, better than nothing. Since the balance bar will put all the stroke to the empty circuit until that master bottoms then it pushes on the master with pressure still. If the balance bar is driver adjustable you can crank it over and be "fine" though. One other problem is if you dont have enough range of motion on the yolks that connect to the balance bar you can bend the **** out of the master rods. But you'd hopefully discover that issue when bleeding the brakes... like last year's WPI fsae team, that was an interesting call to get at 1am, "we broke the master cylinders do you know where the spares are..."

Seefo

iTrader: (5)

how is the bias adjustment a bonus? you can do that with a single master... Is there an advantage for the dual that I am not seeing in this comparison?

mx5-kiwi

and

I am not sure these two comments are on the same page .......