manual brakes, booster choices...
 

i was set on upgrading to manual brakes (no booster) using a 929 master. but at a price of over 100 bucks. i can easily uprgade to a much better MC for cheaper. better and cheaper? yes!

theres plenty of options on this link below. im am looking at the 1" bore part # 260-10375

http://www.wilwood.com/MasterCylinderList.aspx

i will fill in all the existing holes for the stock brake booster and redrill the 3 small holes to mount this MC. then adapt the stock brake pedal to it or maybe spring for a nice wilwood pedal. later on upgrading the stock clutch master to an identical wilwood one. maybe a reverse mount to further clean out the engine bay.

anyone have any suggestions? maybe its to large/small a master?

oh, this is for a 72 Rx2...

A 1" may be big to go without a booster. You need to go down in master size to increase the line pressure without needing a leg like a horse.

My FC race car has 5/8" front and 7/10" rear masters on a bias bar pedal set up.

929 Master details
 

I found a 929 in the yard so I took the master off and took some measurements and photos.

https://www.rx7club.com/attachment.p...1&d=1259431036
https://www.rx7club.com/attachment.p...1&d=1259431036

i thought at first 1" might be to big also. but also the smaller the bore, the more pedal travel i'll have. so if i just use the right bore size, stroke, with a correct pedal ratio, it shouldnt be so bad. same principle as a small ratchet Vs. a long breaker bar. the length gives you the torque you need to apply pressure. and the stock pedals on the Rx2 are pretty long.

the only thing im worried about is it only has one outlet for brake lines. so would i have to Y it off or something for front and back brakes? or are two needed, one for front one for back?

That particular part# is for dual master cylinder setups. You really want to have two outlets that feed from separate fluid "chambers" (as wilwood calls them).

Every sanctioning body requires the front and rear brake feeds to be pulled from separate reservoir. May even be a DOT rule.

-billy

You're thinking leverage, and yes you need the right amount from the pedal to start. Most pedals with a booster will have about a 5:1 ratio, without a booster they'll be in the 6:1 range. Measure the distance from the fulcrum to the hole the master attaches to and then the distance from the fulcrum to the foot pad. Divide the foot pad distance by the master distance and you have your ratio.

There is a lot of math involved and a little bit of experience of what works to get things right. A 'light' pedal will need about 70-80lbs of pressure from your foot, a 'heavy' pedal will be in the 110-120 range.

You don't want your entire brake system on one circuit from one master(all stock masters are two circuit). Besides the safety issue you will lock up the rears without some kind of bias adjustment/valve.

hmmm.... so i still would like to have a manual brake set up. but i do not want dual masters.

anyone reccomend a single master that will do the job? aftermarket or factory from some random car. i can fabricate my own pedal for correct ratio if needed.

thanks for the tips so far...

Air cooled Porsche 911's came with no booster People seem to like how those work well enough. These may work well as a design model. FYI, the majority use a 19mm master.

What calipers are you planning to use?
Piston areas will be key to moving forward with this exercise.

Are you playing with the diameter of your rotors as well?
Bigger rotors would need less pad force for a given wheel diameter.

If you want to move forward I'd recommend writing an Excel spreadsheet. Then you can just play around until you get the numbers you want, buy parts, cross your fingers and hope it works.

im not changing anything at the moment except for the master cylinder. The Rx2 i just picked up is missing it but has everything else. and i dont wanna spend time and money searching for an original one. so i decided to just upgrade and clean it up at the same time with a better master and no booster...

im thinking the 929 or similar might be the best choice. since most of the aftermarket set ups require 2 masters and P. valves to work correctly. it would just simplify everything.

Did you just pick up a car from Chad in TN?

Stock parts is going to be the "simple" way to do this. By the time you get a master cylinder, bias adjustment and convert the brake lines.

I have a few rx2 boosters, and I believe a master cylinder laying around. Master would need a rebuild, you can get kits from your local auto parts store.

If you are dead set on an aftermarket cylinder without boost you need to look at the units towards the top of the list on the page link you posted. Those have separate reservoirs.

-billy

yeah, got it from Chad.

as you can see from my posts. im pretty undecided on what im going to do. all i know is, i dont want to put a stock one and im pretty set on manual brakes.

im not sure what im doing as of now. im exploring my options and of course a wilwood set up would be better than a junkyard part. but after the pedals, dual masters, ect... that can be pricey. maybe is should add that to my x-mas wish list!

You will need to go with a smaller master than stock if you're getting rid of the booster. IIRC the 929 master trick is done to the FC's and they keep the booster.

Look into old VW masters or things like that. Stuff that had discs and no booster stock. A 19mm /3/4" or so might get you in the ballpark. A 17mm if you find metric stuff will probably be better. Don't worry too much about pedal travel, people get hung up on that and end up with a pedal that is too hard. A well thought out system with braided lines and good pads will give you a great pedal and stop the car without being a pain in the, uh, leg.

For new lines if the metric ones are too expensive I just buy long standard thread units and adapt one end to metric fittings if I have to. I'll even reuse the stock fittings if I can. If I can't reuse the stock fittings I buy the shortest metric line I can and cut it apart for the fittings. That can be cheaper than buying individual fittings. I nice pipe flare kit is your friend when making a new brake system.

double-flare that is. pipe cutter and double flare kit from harbor freight is cheaper than any other store but works very well.

whenever you get this problem solved take pictures an post them up. im in the middle of my rx-2 project as well, this would help greatly.

Chad who? he he
And yes, I would have to agree with billy on this. At least if you went back stock it would allow you to get the brakes back and then later you could research the other side of it. Billy's family has been in the rx2/rx3 game awhile so it there was an easy way Im sure he would know it.

^thats true. better to just go back to stock for simplicity. and then finish up my research and choices for a manual set up later on.