Madjak

If you are doing a booster delete you may as well drop in a balance bar and go with dual masters. I don't see much point going half way. It's not that much harder and gives you so much more reliability and tweaking options. Plus in cockpit bias adjustment and far simpler brake lines with isolated systems.

Modifying the stock pedal box is easy enough for anyone who has a drill and a hole saw. The only difficult bit is welding on some additional bracing the pedal box once the required metal has been removed and welding the balance bar tube into the stock pedal. The dual masters will bolt up through the existing holes in the chassis with just a thin blanking plate required. You also need to hole saw the chassis to make room for the masters.

The hardest part is bolting it all up and then bleeding it.

aidandj

iTrader: (5)

I don't necessarily disagree with that, but just saying that those aren't just copper lines.

freedomgli

If you're going to go manual brakes with dual master cylinders then I don't see the point in modifying the stock pedal box. In for a penny, in for a pound. https://www.miataturbo.net/race-prep...5/#post1352056

Truthfully, I get that not everyone wants to re-engineer the entire braking system from the pedal to the wheel. But you do reach this point of diminishing returns. It kind of reminds me of using RRFPR with stock injectors and an Apex'i S-AFC instead of a MS3 and bigger injectors.

Madjak

Well sort of. A non factory pedal box install is a big undertaking. Getting it positioned correctly and fabbing up mounting points is no easy task, even getting it to fit around the steering column and accessibilites are an issue.

In terms of level of difficulty installing a balance bar is not much harder than just the booster delete and gets you 90% of the way in terms of capability to a full pedal box replacement. It is probably a bit more expensive as you need to purchase the biasing bar and masters but it's far far more useful on the track. The benefit of the aftermarket pedal box is being able to place it where you want and the rigidity.

In some respects having the masters visible and accessible is preferable so that you can do easy visual checks and not needing a physio apointment afterwards.

soot

A couple of things:

- Yes, that is NiCopp brake line. Yes it is awesome and super easy to work with.

-The bias valve will be hard mounted. Hell no do I want to risk that braking off, but I do not have access to a shop at the moment to make a bracket. The car is parked for now until I can get somewhere to make something less hacky than I can make in my room.

-I would have loved to do a dual master setup, but I bought this kit because it was supposed to be bolt on since I lost my garage. I have a couple of spots I can show up and use a welder/shop for short durations, but not long enough to finish a dual master install with welding, etc. Unfortunately this kit is not bolt on... I'll likely either route the lines into the cabin and mount the bias valve there, or move to a dual master setup when I have a better shop situation.

Edit: I know it's not a great setup, but it's what I have for now. I had to work with the fittings I had on hand, things did not work out as planned and I'm on a bit of a time constraint. If anyone wants to post up their dual master balance bar setup it would be nice to end the thread with a bit less fail.

hi_im_sean

iTrader: (3)

Im so glad I read this. This has been one of my biggest complaints about braking, and I couldn't quite figure out why. I was told by a few people that's just how brakes are on track, I knew that couldn't be right. Thanks Hector.

Madjak

You can easily test a booster delete by unplugging the vacuum line and blocking it with a bolt to top the intake manifold sucking air through it. Removing the booster itself only removes a little extra resistance.

USE LOTS OF CAUTION WHEN YOU FIRST TEST.

Manual brakes require a lot of initial force to start slowing the car. It's alarming the first few times so make sure there is no one around. It takes a while to get used to the higher pedal pressure required.

soot

If you're using a master that's the same diameter as stock, you'd need to also change the pedal ratio to make the brake effort reasonable. The factory MC is too large of a bore without a booster. My Wilood MC was the same diameter as stock, so I had to drill a new hole for the clevis 15mm higher on the pedal.

Madjak

I ran my car for several events with the vacuum line of the booster disconnected. Once I was confident I preferred the manual brakes over boosted I set up the dual masters at the right sizing to reduce the pedal force but it's not a lot different from that initial test. I still recommend people try it before moving completely removing the booster given it's so easy to disconnect and plug the vacuum line.

Next time my dash is out I'll be moving the top pivot downwards 12 - 15mm rather than the clevis upwards. I like the clevis to be as close as possible on the centerline of the masters.

573

iTrader: (2)

One thing I either missed or haven't seen mentioned is that most of these manual brake kits include master cylinders with only a single output. This is dangerous and doesn't meet OEM standards because the entire brake system is hydraulically linked. A single leak could result in your brakes being totally lost.

The OEM configuration uses a tandem master cylinder, giving you two hydraulically isolated braking circuits. This is much safer because if one fails you still have the other to slow you down.

hi_im_sean

iTrader: (3)

There is a whole range of 2 bolt flange tandom masters that come in a variety of bore sizes for things like a 1993 dodge daytona, available on rockauto for less than $40. Commonly known in the GM metric chassis world, as the Mopar Manual Brake Master swap. Checking the flange compatibility for miatae is something aidan and I have been meaning to do for quite some time. Wilwood sells this exact master, as a universal for about $120. If the bolt pattern is the same, or if it can be slotted, this will open up a huge range of cheap, and safe options. Someone want to get me those dims? And I can measure the mopar master I have at home, later today.

Savington

iTrader: (31)

In theory, sure. In practice, I assure you that one big leak in a front caliper will result in zero braking at any wheel.

Madjak

The tandom systems have a floating piston so if either side develops a leak you basically get no pressure anywhere. You an test this when you bleed the brakes. Crack any brake nipple on the car and the foot goes to the floor.

The only way to have redundant hydralic brakes is to run dual masters with an angle limit on the balance bar. I know with my system I can have zero front pressure but the rears will still work fine because of the mechanical limit. It makes bleeding the brakes a big challenge until you figure out you have to do both ends at once.

Leafy

iTrader: (1)

Screw a pedal box to do balance bar. Like I linked, that VW bracket should bolt in place of our booster if the chase bays kit fits. Its off the shelf, albeit from england. I'm sure someone must sell one over here since it should fit a **** ton of cars.

Madjak

Part of the reason why I removed the booster was for space considerations, but for the LHD miatas that isn't really an issue.

I had another look at those brackets as I didn't really look at them that closely before. There is an RX7 one with longer studs which would probably be ideal and as you say I bet it will just bolt up through the existing holes. I'm pretty sure the RX7 boosters are interchangeable with ours. Someone needs to try one and see how they go as they do look like a very good option.

soot

This would be so awesome. I assume you're looking for the bolt spacing for a 'universal' Wilwood MC? I can get you any measurements you need off of mine if that would help. Also, Wilwood posts full dimensions for all of their MCs online as far as I know.

e.g. below.

Leafy

iTrader: (1)

They do seem to have a USA sales division, or at least a usa sales email.

hi_im_sean

iTrader: (3)

No I need the miata dims. I can get them myself, just didn't want to dig the miata out. Ill try to get some **** done tomorrow, its my day off.

hector

I don't have my car to take any measurements or even pictures but we swapped in a tandem master with the right brake line sizes instead of the right spacing. My co-driver made an adapter plate from aluminum that bolted to the firewall and pedal assembly then bolted the new master to that. Same 4:1 pedal ratio with 11/16" master feels good for street driving and autoxing. When we did it I did not notice that the Solo rules allow you to drill an additional hole in the pedal. It would only be a 1/2" higher as the same rule says nothing about clearancing the firewall but even this would be about 4.5:1 ratio. This may have worked with the 3/4" master that we tried first which I found too firm for street driving.

M2Ken

MAZDA MX5 HYDRAULIC BIAS BOX & KIT B WITH LINES CMB6331-KIT-LINES | eBay

i have no idea what master cylinders are sourced for this, or what math was used in putting this kit together. However, it appears to offer an interesting option if you are deleting the brake booster.