Were the assisted brakes always standard or was there a 1st gen with manual brakes?

I am asking because I have converted an 85 GSL to plug in electric and really don't want to add a vacuum pump to the car if I can avoid it. I have been driving the car for about 6 months now without a vacuum pump and apart from the brakes being a bit stiffer than I like it works fine. I can lock up the wheels if I really need to. I believe part of the stiffness comes from the vacuum assist assembly. I have replaced the master cylinder which is easy on these cars. I have not ever removed the vacuum assist mechanism to see how the brake linkage connects. I am guessing that if there was a non assisted version that there would be a different master cylinder that I could get that would just bolt to the existing pedal mechanism. Another possibility would be using a master cylinder from an older mazda, (RX-4, Cosmo, GLC, something compatible) if it will just bolt in place. I would just install an electric vacuum pump which I have purchased if this would require a lot of fiddling.

Thanks!

 

Hi there i would say that you can just remove you vacuum assist and bolt the original brakecylinder to the torpedoplate.. it is also quite easy to put to mastercylinders on the car with two resouvoirs and a balancebar then you can adjust to your demands. but if you only want one you should messure the original piston and buy a larger one just a millimeter ore 2 bigger should give you a easiere braking..

I hope my English is understandable

best Regards Rasmus from Denmark

 

the RX-7 has always had power brakes. 79-95's all had them regardless of whether they were rear drum or rear discs.

 

Mazda had power brakes Rx2 and newer...

however, i've run my car with no vacuum to the booster, and you need a little muscle but its fine, although my Triumph had manual brakes stock...

i think converting to non power would be really easy, you just need a longer pushrod, and you'd maybe want to move it on the pedal (manual brakes usually have a different pedal ratio, Jgrewe has posts about that, i haven't had my coffee yet.

i've seen people mill aluminum blocks to adapt the stock master to the firewall, which i think is what our dutch friend means by torpedo plate.

 

Thanks for the reply. So what you are saying is the Master Cylinder has the same bolt spacing as the vacuum assist assembly so it would just be making a couple of hard lines to fit the new Master Cylinder location? I guess I would need to find some way to support the line splitter since it hangs off a bracket on the front of the vacuum assist chamber.

 

That is what I thought but it never hurts to ask. For the American market I suspect they would have ruled out a lot of sales if they didn't have this pretty much standard.

Thanks for the verification.

 

So unlikely to find a MC that would fit from an older Mazda before power brakes were standard.

Like I said I've been driving it with no vacuum for about 750 miles now and as you say it needs a little muscle but it really isn't a problem. The problem is I have another car and the habits you have in one car you have in the other. Since I am driving most of the time without the assist when I get in the other car it takes a bit to not, shall we say, apply the brakes excessively!

I think quite a bit of the resistance is from the vacuum assist assembly because in addition to applying the brakes you also have to overcome that.

I will probably just go ahead and put in the electric vacuum pump and leave this for a future project. I have a lot of things to do that are more important than milling an aluminum block to match stuff up. Things like getting the heater working.

The sounds you hear in an EV are completely different. Things you never hear in a regular car. The surprising ones are the noises from the gearbox and differential and even the speedometer cable. At highway speeds it is wind and tire noises. And you always hear other cars. I would hate to spoil this with a noisy electric vacuum pump.

 

WHO SAID IM DUTCH thats the guys with the legal weed.

But yes i ment firewall.

I was a little wrong it will not fit directly on the firewall (i was doing a opel Ascona B and mixed up) you are gonna need to construct a metal plate for adapting the brakecylinder.
I will get you some pictures off my 2 mastercylinders wich is quite easy to mount on the original "pedal box" you only need a cup drill and a few hours. But i dont know the rules for street cars in your country iff you ar allowed to do stuff like that in denmark almost no changes to a car is legal and certanley not on the braking system.

Best Regards Rasmus

 

you'd need an R100 master cylinder, and its probably not easy to get one of those! i do agree the vacuum booster is probably hard to push, in fact i tried it off the car, and by hand its not pushable, although if you apply like 2psi of vacuum it moves pretty easy.

it would suck to ruin the gearbox whine with a vacuum pump

 

lmao! sorry i thought that said the netherlands, my English isn't so good

 

What ever you do don't leave the booster hooked up and not working with vacuum . In a panic braking situation you will be in someones trunk before you get the darn thing pushed hard enough to activate the brakes proper . They seem to work fine until you really need them then you are screwed. Why not remove the diaphragm from the booster and use as is ? ( that is a question not a statement ) Gerald m.

 

A smaller bore on the master cylinder will give you more brake pressure, a larger bore gives you less pressure, and a firmer feel. Kinda cournterintuitive The advantage of a bigger master cylinder is that it has more volume, which is only helpful if you switched to 4 pot brakes calipers from 1. A smaller master makes the brake pressure go up, the pedal travel further and you can brake harder with no power brakes. A larger master makes the pedal travel less, less total brake pressure, pedal feels firmer. You have an 85gsl, with a 7/8 bore master, you could switch to an 83 gsl master cylinder with a 13/16 bore and the that will help a little. But I believe it has different fittings for the brake lines...


This helps explain it
Mark Williams Enterprises - Brake Technical Information

I believe this is your master cylinder 85 gsl w rear disc
More Information for CENTRIC 13045104

This from an 83 gsl w rear disc is smaller and I think maybe it will fit, but one of the lines needs a new fitting, and I'm not sure about the rest.
More Information for CENTRIC 13045103

You could maybe just pick an off the shelf wilwood master and proportioning valve from summit and do it all custom... The danger od goint too small on the master cylinder is making it so you the pedal travels so far you hit the floor before you lock up the tires in an emergency braking situation.

Weirdly enough, I actually built an EV from an FB, too. An 85 gs. A few years ago. I ended up getting a cheap vacuum pump from surplus center online, a vacuum switch, and mounting it inside an mdf box i built. I could only hear it if I really listened for it.

 

It is a good question too. And the answer is I didn't know this is an option. I've been driving since 1972 but I only started working on cars when I started doing this EV conversion in 2011. I guess I would consider myself a car guy now. Before that the deepest I ever got into a car was changing out a leaking front transmission seal and clutch on a 63 ford econoline van. That was easy but unpleasant so is probably why I avoided similar tasks. Now I find working on cars is therapeutic.

Thanks

 

Well I don't know that it is an option it just seems a lot easier than the rest of the options , you might be just as far ahead and remove the booster vacuum valve from the booster ( I think someone might have mentioned that )( the fitting that the vacuum hose attaches to), that should be much easier than removing the diaphragm then if you no like you can just put the valve back in and buy the vacuum pump It only takes 2 or 3 inches of vacuum NOT PSI to operate the power brake system . That said I do think that it is poor practice to screw with the brakes in any way. GOOD BRAKES SAVE LIVES . Gerald m.