rwatson5651

iTrader: (5)

Good information!!

I have been searching for MC s that would work and not having a lot of luck.

The booster swap is a little more complicated for me as my car is an SA which came with a tiny booster and the clutch master sits too close to the booster to allow one of much larger diameter without reworking the firewall to move the clutch master.

Plus I'm thinking if I go up in booster size along with MC size the larger booster will negate the firmer pedal I will get from the larger master.

I will check out clockker's post to see what I can learn. Thanks.

I noticed that your booster has no vacuum source connected to it, do you run it this way? This could be helpful for me. I may be able to deactivate my booster to help me get the firmness I need. Had not thought of that alternative. I may be able to just do a booster delete. I think I have seen a kit from a vendor to help with this. Techno Toy Tuning? Deleting the booster may lower the diameter of the MC I need into the range available with vertical mounting lugs.

rwatson5651

iTrader: (5)

Here is the part I was thinking of:

https://technotoytuning.com/mazda/fb...ater-sa-fb-rx7

It looks like it will allow the use of either vertical or horizontal MCs so I could go up and down in bore size indefinitely till I get the perfect feel. Thoughts?

j9fd3s

iTrader: (3)

everything Rx3 SP or newer has the same brake booster mounting, and since clokker has uncovered the subaru and honda also share, i do mean everything. ALL Mazda's 78-now, Subaru from ? to now, honda from ? to now, and also the fords*.

the only thing you need to watch out for on the SA, is that if the booster gets too big it hits the clutch master, as detailed in the competition manual

*due to some badge engineering there were a bunch of Mazda's with ford boosters, tribute being the chief one. i know its the same pattern, as its also the booster we sold the most, because it says ford on it. all the other 4 letter words were taken....

LargeOrangeFont

iTrader: (7)

I do run it with the vacuum plumbed to the intake manifold. That picture was taken befor I had the car running. Be aware there is a check valve in that hose so you still have a couple pumps of assisted braking if the engine shuts off. Just remember to cut the hose open, remove the valve and shove it into your new hose when you do a booster swap.

rwatson5651

iTrader: (5)

Thoughts on deleting the booster?

valley

iTrader: (1)

As in running manual brakes?

At the absolute least, if you're lucky, you might be able to get away with changing the pivot point of the brake pedal and a custom pushrod for the MC. More likely you'll have to more or less "redesign" the the brake pedal, all associated hardware, and find MC(s) that will work with the specifics of your vehicle, that is weight, balance, calipers, etc.

Most people, when switching to manual brakes buy a new pedal assembly, have it custom installed, speak with who ever makes the MC(s) they're buying to find good MC(s) to start with, then spend time dialing them in with a bias bar or proportioning valve. Depending on how expensive you're going you could be looking at multiple thousands of dollars. Depending on how much you can do yourself you're still looking at a minimum of ~$300 (my off the cuff guesstimate).

It's a lot of work and time.

If you want to delete the booster without doing any of this... well... find a deserted area, disconnect your booster and drive around, SLOWLY, and try to stop.

rwatson5651

iTrader: (5)

My plan would be to do just what you discribe on the pedal to get the ratio right, (I have found guidlines on brake design websites) then use the Techno Toy Tuning booster delete adapter (see above) and use a single master,rather than the dual master/balance bar) , use the calculators I have found online to help determine the bore diameter and install an adjustable proportioning valve to get the balance right. I could experiment with different bore diameters to get the firmness I am looking for while still providing enough volumn for the four pot calipers I have in front, without wasting too much money. The 3T part lets you use a wide variety of MCs with either a vertical or horizontal lug set up so I could go to any size that makes it work. I have spare pedal boxes and I can weld and have access to machining equipment. So I think it may work, as crazy as it sounds. It will allow me to tweak things to get the very firm pedal I'm looking (read firm pedal even with pads with very high friction ratios) and good front/rear balance. Mind you I have not decided to go this route yet, just considering all alternatives.

And yes, I probably would experiment with just disconnecting the booster as a quick test to see if they would compensate for the very soft pedal / early lock up that occured when I installed the HP Plus pads recently. Certainly in a deserted area...

rwatson5651

iTrader: (5)

Or I may just install an adjustable prop valve and a larger MC that will bolt to my SA booster and see what that does. At this point I am just considering my alternatives.

j9fd3s

iTrader: (3)

the SA/FB booster is just there for decoration, you can put a PP engine in, and forget to put a booster line on the manifold (twice!) and you won't really notice much difference. its still a softer pedal than my manual braked Tr3.

the FC is completely different, FC with no booster is undriveable. i know a guy who sells booster deletes too, they are for a toyopet but i think they will work (if not i can give him the right measurements)

valley

iTrader: (1)

Sounds like you've some good avenues to explore then, good luck and let us know how it goes!

Odd, it sounds like the booster has an remarkably low assist then...

j9fd3s

iTrader: (3)

it basically makes the pedal mushy. i should mention again, that the SA/FB are a little unique there, the FC is not driveable without the booster

rwatson5651

iTrader: (5)

I have been checking the specs of the pedal assemblies I have to see what modifications would be required to go manual. The SA pedal is a 6 to 1 ratio and the FB is a 5 to 1 ratio and can be modded very easily to provide a 6.25 so I could adjust either direction very easily. The Wilwood people recommend starting with 6 to 1 so I am right where I need to be. That leaves the only other variable the bore of the MC which I should be able to predict with the calculators online, if I have to I can adjust. I see this as the conservative alternative, but I have to admit I am really digging the aftermarket twin master setups I am seeing on the websites!!

mustanghammer

iTrader: (3)

I would focus your efforts on making the single master work with or w/o power. I have installed dual master and triple master setups in two different cars and it is not easy to do. Even if you do one that puts the masters in the engine compartment there is allot sheet metal surgery involved. Also, the OE gas pedal/throttle cable assembly is generally in the way of the way of the brake bias adjuster cable on the aftermarket pedals.


All of these things can be dealt with on a gutted race car. But on a street car with all the wiring and an HVAC system would be a real PITA.

rwatson5651

iTrader: (5)

That's exactly what I have decided to do. I have ordered the Wilwood adjustable proportioning valve and have decided on the 7/8 in master and have sent e-mail to Techno Toy Tuning to confirm the spacing of the mounting holes on their "brake booster delete" adapter before I actually order it. I was just too concerned about cutting up the firewall on a car I have owned for 35 years, so I decided against the nifty two master setup. I still may spring for a single wilwood master cylinder, just to get that perfect racy look under the hood. LOL....

But seriously, I have learned a lot about engineering a brake system through all of this. I just got through running all the math to determine my line pressures and clamping force computations to determine how much different the clamping forces will be with no proportioning, looks like it will be approximately 67% front/ 33% rear which seems to be in the ballpark. Also helps estimate how much pedal pressure will likely be required, hoping to get it perfect with the first master I try, still a guessing game however.

Oh, and I also learned how to spell pedal LOL....

Here is a question for you,

How many deceleration gs should I expect on street tires (Yokohama Ado8r) if/when I get the balance right? I have been playing with my new lap timer that shows g forces and I have only been getting about .6 or so. Seems way to little to me. Hoping to get as much as .9, 1.0 or higher, is this realistic?

LargeOrangeFont

iTrader: (7)

I did recently did -1.05g with 100 tread wear tires and was not braking as agressive as I could have. I am pretty sure I have done higher in cooler weather, I'll have to look.

j9fd3s

iTrader: (3)

here is one of ours i'm assuming since its just the one lap, and nobody crashes its the winning one. since the G thing, isn't labeled, i'm not sure if the inner circle is 0.5G or 1.0G (outer would then be either 1.0g or 1.5g)

not sure it matters, notice turn 1 right in the beginning is the hardest braking? it happens first thing. also notice that there isn't anywhere else on the track where there is braking in a straight line? also if you drew the "traction circle" ours is shaped like a pyramid (it would be a diamond if the car accelerated), only turn 11 (big hairpin near the end) does the G spot follow the line.

the car is a miata, on 225 hoosiers, a fat cat double condom setup (with the ohlins he can flat 9-10). hp for this run is 133 on the dyno* they had that day, which was reading high, so its probably like 120rwhp. if we overlaid your FB data, i think the FB is faster (notice lack of acceleration G's?), the miata will have more lateral grip because its got stickier tires, slightly. car is just under 2400lbs with driver


*we are allowed a certain weight and hp, and they dyno us at the nationals. this part is ok, the part that isn't ok, is that the dyno they use is +/-20hp. the miata dynoed 147hp one weekend, and 120hp the next, and then 138 the weekend after that. they say its not possible to have that big of a swing, but it apparently is.

peejay

Your cars must be way different than mine then One of the things I'm used to doing with my car is blipping the throttle every now and then to build brake assist.

But the takeaway I am getting is that I can bolt in a manual brake setup from a Subaru if i find one, maybe just have to redrill the brake pedal to get a 7:1 ratio instead of the stock 5.5:1. (I think FC are 4.5:1)

j9fd3s

iTrader: (3)

well there are three things going on. the first is that there haven't been any manual braked cars in our driving lifetimes. the second, is that my Tr3 had manual brakes, and they were great, pedal effort was a little higher than you're used to, but not by a lot. or maybe i should say that pedal effort starts normal, but goes higher linearly with braking force, where a power braked car doesn't.

the third thing, is that mine is an 82, so its got a different booster/pedal setup, but P port 2 is an 85, so this is kind of moot

or maybe you're not pumped up enough?

peejay

I drive enough of them... and Chevy made manual brake S10s in the 80s.

I like getting into a big block 60s car with manual single-stage brakes and 9" drums. Actually works pretty well, but the very idea gives modern people the vapors

But if a Subaru booster bolts up, then maybe there's a manual brake solution made for the rally guys who convert to manual brakes because their engines don't ever make vacuum except on transits when they turn the antilag off.

j9fd3s

iTrader: (3)

the brake booster pattern seems to be pretty universal, we know Mazda uses the same pattern from the Rx3 SP on, and junkyard honda, subaru (mid 90's to 2015's), and then the fords that Mazda sold fit too (Tribute, don't buy one though, we sold a lot of those, they go bad all the time).

since it seems to be generic across such a wide range, one wonders if every car has that pattern. for a funnies, just based on working on different cars, you'd expect GM to use something wildly different, like a snap ring, or a 2x4. Mercedes would use the same pattern a 1937 Chrysler had*, its what Mr Hilter bought them, and he hasn't approved a change. BMW would use whatever ATE put in, so nobody knows. the British one would bolt it in, using the same pattern, but it would made of something that is flammable, even when its wet, which it will be. it will also be rusty and oily. on a Lada, the brake booster, is the friend you have to make sure the car doesn't get away from you when you push it down hill. audi/VW would use whatever "fell off the truck", there are probably 7 bolt patterns in that firewall.

*the automatic transmission Mercedes had in the 60's was from a 30's chrysler, they used it into the 80's.